Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 16 (2014)

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1 Aliphatic Nitriles1 Acute Exposure Guideline Levels PREFACE Under the authority of the Federal Advisory Committee Act (FACA) P.L. 92-463 of 1972, the National Advisory Committee for Acute Exposure Guide- line Levels for Hazardous Substances (NAC/AEGL Committee) has been estab- lished to identify, review, and interpret relevant toxicologic and other scientific data and develop AEGLs for high-priority, acutely toxic chemicals. AEGLs represent threshold exposure limits for the general public and are applicable to emergency exposure periods ranging from 10 minutes (min) to 8 hours (h). Three levels—AEGL-1, AEGL-2, and AEGL-3—are developed for each of five exposure periods (10 and 30 min and 1, 4, and 8 h) and are distin- guished by varying degrees of severity of toxic effects. The three AEGLs are defined as follows: AEGL-1 is the airborne concentration (expressed as parts per million or milligrams per cubic meter [ppm or mg/m3]) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic, nonsensory 1 This document was prepared by the AEGL Development Team composed of Cheryl Bast (Oak Ridge National Laboratory), Julie Klotzbach (SRC, Inc.), Chemical Manager George Rodgers (National Advisory Committee [NAC] on Acute Exposure Guideline Levels for Hazardous Substances), and Ernest V. Falke (U.S. Environmental Protection Agency). The NAC reviewed and revised the document and AEGLs as deemed neces- sary. Both the document and the AEGL values were then reviewed by the National Re- search Council (NRC) Committee on Acute Exposure Guideline Levels. The NRC com- mittee has concluded that the AEGLs developed in this document are scientifically valid conclusions based on the data reviewed by the NRC and are consistent with the NRC guidelines reports (NRC 1993, 2001). 13 

14 Acute Exposure Guideline Levels effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure. AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including sus- ceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape. AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including sus- ceptible individuals, could experience life-threatening health effects or death. Airborne concentrations below the AEGL-1 represent exposure concentra- tions that could produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsen- sory effects. With increasing airborne concentrations above each AEGL, there is a progressive increase in the likelihood of occurrence and the severity of effects described for each corresponding AEGL. Although the AEGL values represent threshold concentrations for the general public, including susceptible subpopula- tions, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to idiosyncratic respons- es, could experience the effects described at concentrations below the corre- sponding AEGL. 1. GENERAL INFORMATION FOR SELECTED ALIPHATIC NITRILES In this chapter, the bases of the AEGL values for the following five aliphatic nitriles are described: acetonitrile, isobutyronitrile, chloroacetonitrile, propi- onitrile, and malononitrile. Information relevant to all five compounds is first pre- sented, and is followed by separate sections on the individual chemicals. 1.1. Absorption, Distribution, Metabolism, and Excretion Aliphatic nitriles are readily absorbed from the lung and gastrointestinal tract, resulting in systemic toxicity. Most of the systemic toxicity of these ni- triles is mediated through hepatic and extrahepatic cytochrome P450 catalyzed oxidation of the carbon alpha to the cyano group producing a cyanohydrin and an aldehyde. The metabolically-liberated cyanide is then conjugated with thio- sulfate to form thiocyanate and is excreted in the urine (NTP 1996). Studies con- taining nitrile-specific metabolism information were available for acetonitrile, propionitrile, and chloroacetonitrile and are described below. No chemical- specific metabolism studies were available for isobutyronitrile or malononitrile. 

Aliphatic Nitriles 15 1.1.1. Acetonitrile In humans, studies of smokers suggested that 91 ± 4% of the acetonitrile inhaled in cigarette smoke was retained and that a significant portion may have been retained in the mouth (Dalhamn et al. 1968). Also, human poisoning cases suggest that acetonitrile is well absorbed by both inhalation and dermal routes but provide little quantitative data (see Section 2.3.1). Studies in monkeys, rats, and dogs have shown cyanide in the blood and thiocyanate in the urine following exposure to acetonitrile by injection or inhala- tion (Pozzani et al. 1959). The rate of cyanide release from acetonitrile is slower than for other nitriles (Ahmed and Farooqui 1982; see Section 1.4). Peak blood cyanide concentrations occurred 7.5-h after exposure to acetonitrile whereas peak levels occurred 1 h after exposure to comparable amounts of other nitriles or potassium cyanide. Also, the percentage of acetonitrile excreted in the urine as thiocyanate was lower than that for other nitriles, even when the initial dose was greater. These data suggest that the toxicity of acetonitrile is less than other nitriles because of its slower conversion to cyanide and thus more efficient de- toxification to thiocyanate (NTP 1996). Studies of male rats found free and conjugated cyanide and unchanged ace- tonitrile in various tissues after inhalation or intraperitoneal injection (Haguenoer et al. 1975). Ahmed et al. (1992) found acetonitrile and metabolites in the liver, kidney, gastrointestinal tract, gallbladder, and urinary bladder 5 min after admin- istration of 2-[14C]-acetonitrile to mice. At 24- and 48-h post-exposure, label was still detected in the liver and gastrointestinal tract, and delayed retention was noted in the male reproductive organs and brain. Elimination acetonitrile occurs mainly through urinary excretion of un- changed chemical and free and bound hydrogen cyanide. Urinary excretion is greatest during the initial 24 h after dosing. However, after intraperitoneal injec- tion, small amounts were detected in the urine of rats for up to 4 days post- exposure. Thiocyanate excretion was observed for up to 11 days post-exposure (Haguenoer et al. 1975). At high inhalation concentrations, unchanged acetoni- trile may be eliminated by exhalation. 1.1.2. Propionitrile Fromont et al. (1974) studied acute and repeated parenteral administration of propionitrile in relation to its distribution and biotransformation to cyanide in the rat. Lethal doses resulted in propionitrile accumulation in the kidneys, heart, testes, and liver, whereas cyanide concentrations were highest in the spleen, lungs, heart, and brain. Mumtaz et al. (1997) administered a tracer dose of 100 μCi/kg 14C-propionitrile intravenously to female Sprague-Dawley rats, and killed selected animals 1-, 8-, or 24-h post-exposure. Within 1 h of administra- tion, peak radioactivity was detected in the duodenum, kidneys, lungs, large intestine, plasma, erythrocytes, stomach, heart, and brain. The animals excreted approximately 5.3% of the dose within 24 h, with approximately equal amounts 

16 Acute Exposure Guideline Levels in the expired air and urine and only trace amounts in the feces. The presence of radioactivity in the gastrointestinal tract for up to 24-h post-exposure suggested enterohepatic recirculation of propionitrile or metabolites. Subcellular fractions of liver, duodenum, and brain showed significant accumulation of radioactivity. 1.1.3. Chloroacetonitrile Male Sprague-Dawley rats were administered chloroacetonitrile at 57 mg/kg by gavage (Pereira et al. 1984). Approximately 14% of the administered dose was excreted as thiocyanate in the urine within 24 h, suggesting that, as with other ni- triles, chloroacetonitrile is metabolized via P450 catalyzed oxidation of the carbon alpha to the cyano group producing a cyanohydrin which leads to hydrogen cya- nide. Male Sprague-Dawley rats were administered [2-14C]chloroacetonitrile in- travenously (Ahmed et al. 1991). Within 12-h post-exposure, 51% of the radio- activity was excreted in the urine, 2.7% in feces, and 12% in expired air as 14 CO2. Only 0.8% of the administered dose was exhaled as unchanged chloro- acetonitrile, and no unchanged chloroacetonitrile was excreted in the urine. Whole-body autoradiography for up to 48-h post-exposure showed persistent label in the thyroid, gastrointestinal tract, testes, brain, and eyes. In vivo and in vitro studies suggest that chloroacetonitrile reacts extensive- ly with glutathione and causes significant decreases in glutathione concentra- tions in treated rats (Ahmed et al. 1989) and mice (Jacob et al. 1998). 1.2. Mechanism of Toxicity The toxicity of the aliphatic nitriles is due to the metabolic release of cya- nide. Cyanide interrupts cellular respiration by blocking the terminal step of electron transfer from cytochrome c oxidase to oxygen. Tissue concentrations of oxygen rise, resulting in increased tissue oxygen tension and a decreased un- loading of oxyhemoglobin. Increased oxyhemoglobin in the venous blood may impart a flush to the skin and mucous membranes. As a consequence, oxidative metabolism may slow to a point where it cannot meet metabolic demands. This is particularly critical in the brain stem nuclei where lack of an energy source results in central respiratory arrest and death. Cyanide also stimulates chemore- ceptors of the carotid and aortic bodies to produce a brief period of hyperpnea. Cardiac irregularities may occur, but death is due to respiratory arrest (Smith 1996). 1.3. Concurrent Exposure Issues As noted in Section 1.2, the selected aliphatic nitriles reviewed in this doc- ument share a common mechanism of toxicity through their biotransformation to cyanide. Therefore, caution should be noted regarding cumulative effects of expo- sure to multiple aliphatic nitriles. 

Aliphatic Nitriles 17 Tanii and Hashimoto (1986) studied the effect of ethanol on the metabo- lism of 20 nitriles, including acetonitrile, isobutyronitrile, propionitrile, and chloroacetonitrile. Male ddY mice were dosed orally with either ethanol (4.0 g/kg) or glucose (7.0 g/kg), killed by cervical dislocation 13 h later, and micro- somes were then prepared from the livers. (A preliminary study indicated that hepatic microsomal metabolizing activity for nitriles reached a maximum 13 h after oral administration of ethanol at 4.0 g/kg. Glucose at 7.0 g/kg was isocalor- ic to the ethanol dosage). The nitrile was added to the reaction mixture and the amount of cyanide released per minute per milligram of protein was determined. None of the nitriles were metabolized when incubation mixtures lacked nicotin- amide adenine dinucleotide phosphate (NADPH). Ethanol treatment stimulated the metabolic rate of most nitriles compared with the glucose control, suggesting that ethanol consumption may enhance the acute toxicity of nitriles. The etha- nol-to-glucose ratios ranged from 1.00 to 1.83 for the 20 nitriles tested. The rati- os were 1.83 for acetonitrile, 1.20 for isobutyronitrile, 1.62 for propionitrile, and 1.54 for chloroacetonitrile. Willhite and Smith (1981) found that subcutaneous pretreatment of mice with carbon tetrachloride (at a dose that effectively destroyed the metabolic ca- pacity of the liver) protected mice against the lethal and toxic effects of intraper- itoneally administered acetonitrile, propionitrile, and malononitrile. Survival of the carbon tetrachloride-treated mice compared with controls was attributed to decreased brain cyanide concentrations. Tanii and Hashimoto (1984) also found that mice pretreated intraperitoneally with carbon tetrachloride were less suscep- tible to the toxic effects of orally administered acetonitrile and propionitrile. In another study, Tanii and Hashimoto (1985) pretreated male ddY mice with olive oil or carbon tetrachloride and then orally administered malononitrile at doses 3-5 times greater than the LD50. Mean survival times were increased and brain cyanide concentrations were decreased in the carbon tetrachloride-pretreated mice. 1.4. Structure-Activity Relationships Because the acute toxicity of nitriles depends on their ability to undergo cytochrome P450 mediated hydroxylation, on the carbon alpha to the cyano group (α-carbon), and because the hydroxylation is a radical-based reaction, acute toxicity of nitriles is related to the structural features that influence α- carbon radical stability. Generally, the nitriles that are metabolized most quickly or easily at the α-carbon are more toxic than nitriles metabolized more slowly at the α-carbon. Thus, the toxicity pattern, in decreasing order, with regard to the type of α-carbon radical formed following α-hydrogen abstraction is benzylic ≈ 3° > 2° > 1°. The presence of a hydroxy or a substituted or unsubstituted amino group on the α-carbon increases toxicity, and the presence of these moieties at other carbon positions decreases acute toxicity (DeVito 1996). Dahl and Waruszewski (1987, 1989) examined the in vitro metabolism of acetonitrile, propionitrile, n-butyronitrile, isobutyronitrile, acrylonitrile, succinoni- 

18 Acute Exposure Guideline Levels trile, and benzyl cyanide. Nasal maxilloturbinate, ethmoturbinate, and liver micro- somes were prepared from 10-16-week-old male F344 rats. The microsomes and selected nitriles were incubated at 37°C for 30 min, the reaction was stopped by the addition of potassium hydroxide, and cyanide concentrations were measured. The rate of cyanide production varied with both the nitrile side chain and tissue source of the microsomes. Except in the case of acrylonitrile with maxilloturbinate microsomes, the maximum rate of cyanide production increased as the number of carbon atoms in the side chain increased. For ethmoturbinates, the rate of cyanide production was the lowest for acetonitrile and acrylonitrile (which had almost equal rates), followed by propionitrile, butyronitrile, isobutyronitrile, and suc- cinonitrile (which had similar rates), and then benzyl cyanide. For maxilloturbi- nates, the rates were the lowest for acetonitrile, followed by propionitrile, isobu- tyronitrile and succinonitrile (which had similar rates), butyronitrile, benzyl cyanide, and acrylonitrile. For liver, rate were lowest for succinonitrile, followed by acetonitrile, propionitrile and butyronitrile (which had similar rates), isobu- tyronitrile, acrylonitrile, and benzyl cyanide. Ahmed and Farooqui (1982) orally administered aliphatic nitriles or potas- sium cyanide at a single LD50 to male Sprague-Dawley rats. Animals were killed 1 h later and tissue and blood cyanide concentrations were measured. Hepatic and blood cyanide concentrations were highest for malononitrile, followed by propionitrile, potassium cyanide, butyronitrile, acrylonitrile, allylcyanide, fu- maronitrile, and acetonitrile. The pattern in the brain differed in that potassium cyanide preceded malononitrile and propionitrile. Hepatic and brain cytochrome c oxidase were decreased and the decreases corresponded to measured cyanide concentrations. Intraperitoneal LD50 values from studies of mice have been reported for several nitriles (Lewis 1996), allowing for the comparison of the relative toxicity of these compounds (see Table 1-1). These data are consistent with the infor- mation described above showing that the predicted rate of cyanide production (Dahl and Waruszewski1987, 1989; Devito 1996) and measured blood cyanide concentrations (Ahmed and Farooqui 1982) correlate with the intraperitoneal LD50 values. TABLE 1-1 Intraperitoneal LD50 Values for Mice Chemical LD50 Acetonitrile 521 mg/kg Isobutyronitrile Not available Chloroacetonitrile 100 mg/kg Propionitrile 34 mg/kg Malononitrile 13 mg/kg Molar ratio of LD50 values: Acetonitrile/Chloroacetonitrile 10 Acetonitrile/Propionitrile 21 Acetonitrile/Malononitrile 65 

Aliphatic Nitriles 19 1.5. Species Sensitivity Data on the aliphatic nitriles suggest that mice, guinea pigs, rabbits, dogs, and monkeys are more sensitive than rats to the effects of acetonitrile. Interspe- cies differences in acetonitrile toxicity may be due to the relative speed of cya- nide formation and detoxification (NTP 1996). Thus, a slow rate of cyanide pro- duction that enables more efficient detoxification may account for the decreased sensitivity of the rat to acetonitrile. Although much metabolism data are availa- ble for rats and mice, direct comparisons of the rates between species are not possible because of differences in cyanide detection methods, different routes of administration, and units used in reporting data (for example, nmol/106 cells vs. ng/mg protein when comparing cyanide formed from isolated hepatocytes from rats vs. mice). No studies that rigorously compared the acute toxicity of isobutyronitrile, propionitrile, or chloroacetonitrile in different species were found. However, available data suggest that mice are more sensitive to the toxic effects of these nitriles than rats. In an acute inhalation study of saturated atmospheres of isobu- tyronitrile (Tsurumi and Kawada 1971), 0/10 rats died after 4 min of exposure, 1/10 after 5 min, 4/10 after 6 min, 6/10 after 8 min, and 10/10 after 10 min. In studies with mice, 3/10 animals died after 0.5 min, 5/10 after 1 min, 7/10 after 1.5 min, and 10/10 after 2 min. No deaths occurred in rats exposed to propionitrile at 690 ppm for 4 h, and the 4-h LC50 was 1,441 ppm (Younger Labs 1978). The 1-h mouse LC50 of 163 ppm (Willhite 1981) is approximately six times less than the concentration caus- ing no deaths in rats exposed for 4 h. Finally, rat oral LD50 values for chloroace- tonitrile are in the range of 180 to 220 mg/kg (Younger Labs 1976; Lewis 1996), whereas, the reported mouse oral LD50 is 139 mg/kg (Tanii and Hashimoto 1984). 1.6. Temporal Extrapolation The concentration-exposure duration relationship for many irritant and systemically-acting vapors and gases can be described by the equation Cn × t = k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). Data were available to derive an empirical value for n for acetonitrile only. An analy- sis of the acute inhalation lethality data for rats was conducted using the dose- response software of ten Berge (2006). This analysis used the concentration- specific data presented in the summary tables of lethal and sublethal effects of acetonitrile presented later in this chapter in Section 2.4.6, which allowed for the inclusion of all rat data except the DuPont (1968) study for which dose-specific data were not available. The value of n was estimated to be 1.550, with confi- dence limits of 0.539 and 2.560. Details of this analysis are presented in Appen- dix A. The exponent was rounded to 1.6, and was considered valid for scaling across time only for rat data because the rate of cyanide release from acetonitrile may vary between species. 

20 Acute Exposure Guideline Levels Data were unavailable to determine an empirical value of n for isobu- tyronitrile, propionitrile, chloroacetonitrile, or malononitrile. In the absence of chemical-specific data, default values of n = 3 for extrapolation shorter durations and n = 1 for extrapolation to longer durations were used to provide AEGL val- ues that are protective of human health (NRC 2001). 2. ACETONITRILE 2.1. Summary Acetonitrile is a volatile, colorless liquid at ambient temperature and pres- sure (WHO 1993). It has a sweet, ether-like odor, with a reported odor threshold of 42 ppm (Ruth 1986). Mean ambient air concentrations of 0.000048 to 0.007 ppm have been reported, and slightly higher values were obtained for urban than for rural air. Single measurements taken before and after burning of brush and straw indicated a 10-fold increase in acetonitrile concentrations in air (WHO 1993). The major use for acetonitrile is as an extraction and processing solvent in the pharmaceutical industry. Acetonitrile is also used as a process, extraction, and formulation solvent for agricultural chemicals, and in the extractive distilla- tion of butadiene. It is also used as a mobile phase in high-performance liquid chromatography and in the separation of chiral systems. It also has minor uses as an intermediate in chemical manufacturing and in photographic applications. The toxicity of acetonitrile is due to the metabolic liberation of cyanide and signs and symptoms are similar to those observed after cyanide exposure. Slight chest tightness and cooling sensation in the lungs reported by one of three male volunteers exposed to acetonitrile at 40 ppm for 4 h (Pozzani et al. 1959) were used as the basis for AEGL-1 values. An interspecies uncertainty factor of 1 was applied because the critical study was conducted in humans. A factor of 1 was also applied for intraspecies variability, because the mild effects were judged to have occurred in a sensitive subject. No symptoms were reported by two other subjects exposed in the same manner, nor when the same subjects were exposed at 80 ppm for 4 h. A modifying factor of 3 was applied to account for the sparse database for effects relevant to AEGL-1. The 4-h AEGL-1 value of 13 ppm was held constant across the 10-min, 30-min, and 1-h durations be- cause no human data were available exposure durations of less than 4 h; thus, time scaling to shorter durations could result in values that would eliciting symptoms above those defined by AEGL-1. A calculated value for an 8-h dura- tion was 14 ppm, which is essentially equal to the 4-h AEGL-1 value of 13 ppm, so an 8-h AEGL-1 value was not recommended. At nonlethal exposures, AEGL-2 effects, described as less than “moderate to marked pulmonary hemorrhage or congestion” were observed in rats (Pozzani et al. 1959). Since no-effect levels for AEGL-2 effects were not identified, AEGL-2 values could not be derived from the available data. Therefore, AEGL- 2 values were estimated by dividing AEGL-3 values by 3. 

Aliphatic Nitriles 21 The no-effect level for maternal and fetal mortality in pregnant rats ex- posed to acetonitrile at 1,500 ppm for 6 h/day on gestational days 6-20 (Saillen- fait et al. 1993) was used as the point of departure for deriving AEGL-3 values. Although the study involved repeated exposures, fetal death can occur during a narrow developmental window and does not necessarily require repeated expo- sures (Van Raaij et al. 2003). Therefore, the observation of increased fetal death after repeated gestational exposure was considered an appropriate end point for deriving AEGL-3 values. In addition, maternal lethality after repeated exposure during pregnancy is also relevant to AEGL-3 derivation, as pregnant animals may have increased sensitivity to acetonitrile compared with nonpregnant ani- mals. An interspecies uncertainty factor of 10 was applied because no compara- ble data for similar exposures (repeated inhalation exposure during gestation) in other species were found. An intraspecies uncertainty factor of 3 was applied because studies of accidental and occupational exposures to hydrogen cyanide (the metabolically-liberated toxicant) indicate that there are individual differ- ences in sensitivity to this chemical but that the differences are not expected to exceed 3-fold (NRC 2002). Thus, the total uncertainty factor is 30. Time scaling was performed using the equation Cn × t = k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). This equation has been shown to describe the concentration-exposure duration relationship for many irritant and systemically acting vapors and gases. An empirical value for n of 1.6 was determined on the basis of rat lethality data that involved exposures to acetonitrile ranging from 15 min to 8 h. Time scaling was not performed for the 10-min AEGL-3 value, be- cause of the uncertainty associated with time scaling a 6-h exposure to a 10-min value. Therefore, the 10-min AEGL-3 value was set equal to the 30-min AEGL- 3 value. AEGL values for acetonitrile are presented in the Table 1-2. TABLE 1-2 AEGL Values for Acetonitrile Classification 10 min 30 min 1h 4h 8h End Point (Reference) AEGL-1 13 ppm 13 ppm 13 ppm 13 ppm NRa Slight chest tightness (nondisabling) (22 (22 (22 (22 and cooling sensation mg/m3) mg/m3) mg/m3) mg/m3) in lung (Pozzani et al. 1959) AEGL-2 80 ppm 80 ppm 50 ppm 21 ppm 14 ppm One-third of (disabling) (130 (130 (84 (35 (24 AEGL-3 values mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) AEGL-3 240 ppm 240 ppm 150 ppm 64 ppm 42 ppm No-effect level for (lethal) (400 (400 (250 (110 (71 maternal and fetal mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) lethality in rats (Saillenfait et al. 1993) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 is without adverse effects. 

22 Acute Exposure Guideline Levels 2.2. Introduction Acetonitrile is a volatile, colorless liquid at ambient temperature and pres- sure (WHO 1993). It has a sweet, ether-like odor, with a reported odor threshold of 42 ppm (Ruth, 1986). Mean ambient air concentrations of 0.000048 to 0.007 ppm have been reported, and slightly higher values were obtained for urban than for rural air. Single measurements taken before and after burning of brush and straw indicated a 10-fold increase in acetonitrile concentrations in air (WHO 1993). Acetonitrile is a combustion product of wood, straw, and other vegetation (WHO 1993). Commercially, most, if not all, acetonitrile produced in the United States is a byproduct of acrylonitrile synthesis by propylene ammoxidation. The amount of acetonitrile produced in an acrylonitrile plant is depends on the am- moxidation catalyst that is used; however, the ratio of acetonitrile:acrylonitrile is typically 2-3:100. Acetonitrile is then recovered as the water azeotype, dried, and purified by distillation. Current acetonitrile production information was not found. Acetonitrile can also be synthesized by other methods such as dehydra- tion of an acetic acid and ammonia mixture, acetamide, or ammonium acetate; reaction of ethanol and ammonia at moderate temperatures in the presence of a metal catalyst; or the reaction of cyanogen chloride with methane, ketones, eth- anol, alkylene epoxides, and paraffins or olefins (WHO 1993). The major use for acetonitrile is as an extraction and processing solvent in the pharmaceutical industry. Acetonitrile is also used as a process, extraction, and formulation solvent for agricultural chemicals, and in the extractive distilla- tion of butadiene. It is also used as a mobile phase in high-performance liquid chromatography and in the separation of chiral systems. It also has minor uses as an intermediate in chemical manufacturing and in photographic applications. The chemical and physical properties of acetonitrile are presented in Table 1-3. 2.3. Human Toxicity Data 2.3.1. Acute Lethality Case reports of lethality from acetonitrile exposure exist; however, specif- ic information about exposure concentrations and durations are not available. Symptoms from acute exposure to acetonitrile before death include chest pain, gastric distress, skin discoloration, tachypnea, hypotension, general weakness, and absence of deep reflexes. Grabois (1955) reported on 16 workers accidentally exposed to acetoni- trile vapors while painting the inside walls of a storage tank. One worker died after two days exposure, two were seriously ill, and other workers experienced 

Aliphatic Nitriles 23 TABLE 1-3 Chemical and Physical Data on Acetonitrile Parameter Data Reference Common name Acetonitrile HSDB 2009 Synonyms Cyanomethane; ethanenitrile; nitrile of WHO 1993 acetic acid; methyl cyanide; ethyl nitrile; methanecarbonitrile CAS registry no. 75-05-8 HSDB 2009 Chemical formula CH3CN HSDB 2009 Molecular weight 41.05 HSDB 2009 Physical state Colorless liquid HSDB 2009 Boiling point 81.6°C WHO 1993 Freezing point -45°C HSDB 2009 Flash point 5.6°C (open cup) WHO 1993 Density/Specific gravity 0.78745 at 15°C/4°C HSDB 2009 Solubility Infinitely soluble in water; WHO 1993, readily miscible with ethanol, HSDB 2009 ether, acetone, chloroform, carbon tetrachloride, and ethylene chloride; immiscible with saturated hydrocarbons (petroleum fractions) Vapor density 1.42 (air = 1) HSDB 2009 Vapor pressure 88.8 mm Hg at 25°C HSDB 2009 Conversion factors in air 1 ppm = 1.68 mg/m3 WHO 1993 1 mg/m3 = 0.595 ppm less serious symptoms. In a follow-up report to this incident, Amdur (1959) re- ported that the tank capacity was 22,730 L (6 meters high and 2.75 meters at its greatest diameter). Due to the viscosity of the paint, it was thinned and heated to 25°C on the second work day; also, ventilation to the tank was stopped. The paint consisted of 30-40% acetonitrile and the thinner was 90-95% acetonitrile. Other components of the paint and thinner included phenolic resin primer, di- ethylene triamine, and mica. The one fatality was a 23-year-old male who had painted inside the tank for 12 h. He was asymptomatic when he returned home; however, he awakened shortly after midnight with malaise and chest pain. Nau- sea, vomiting, and spitting up blood preceded convulsions and coma. He was admitted to the hospital at 9:15 AM with shallow, irregular, and infrequent res- piration; he died within 1 h of admission. Autopsy revealed cerebral, thyroid, hepatic, and splenic, and renal congestion, and a peach-pit odor of all tissues. Cyanide was detected in his blood, urine, gastric fluid, spleen, kidney, and lung. No cyanide was detected in his liver. The two workers who became seriously ill included a 35-year-old male who had painted inside the tank for 3 h and a 28- year-old male who had painted outside of the tank for 12 h. Both men felt well 

24 Acute Exposure Guideline Levels when they returned home; however, during the night or the next day, both men were hospitalized with lightheadedness and semiconsciousness, chest pain, nau- sea, emesis, tachycardia, pallor, shallow or intermittent respiration, and loss of deep tendon reflexes. Both men recovered and returned to work in 10-20 days. Several other workers present at the work site sand-blasted and mixed paint, but were not involved in painting the tank. Symptoms in these individuals included nausea, headache, lassitude, weakness, and chest and abdominal tightness and pain. Dequidt et al. (1974) reported the death of a 19-year-old male worker at a photography laboratory. He had handled acetonitrile in a closed vat for 2 days without problems; however, at the end of the second day, he poured an unknown amount of boiling water and acetonitrile on the floor to clean it. Four hours after work, he vomited and complained of nausea and epigastric pain. The next day he became comatose and had convulsions. Upon hospital admission, cyanide, thiocyanate, and acetonitrile were found in his blood and urine. He died 6 days post-admission despite treatment with dicobalt ethylenediaminetetraacetic acid (EDTA) and hydroxycolbalamine. A 16-month-old boy (11.8 kg) ingested 15-30 mL of false nail remover (“Super Nail Off”, 98-100% acetonitrile, 1-2 g/kg) (Caravati and Litovitz1988). The boy vomited approximately 20 min after ingestion. Assistance was sought from a poison control center; however, the product was mistaken for acetone- containing nail polish remover, and toxicity was expected to be minimal. During the night, the boy was breathing heavily and noisily; he was found dead in his crib the next morning, 12 h after ingestion. At autopsy, moderately severe pul- monary edema was found and cyanide was detected in his blood (3.1 mg/L) and brain (0.2 mg/kg). 2.3.2. Nonlethal Toxicity 2.3.2.1. Case Reports Grabois (1955) and Amdur (1959) reported both lethal and nonlethal cases from inhalation exposure to acetonitrile. These case reports are presented above in Section 2.3.1. Case reports of acetonitrile toxicity from dermal, inhalation, and oral ex- posure to false nail remover (98-100% acetonitrile) are also available. Caravati and Litovitz(1988) reported the case of a 2-year-old boy (12 kg) who spilled 30 mL of nail remover (98-100% acetonitrile) on himself and his bed. Eight hours after the exposure, he was moaning, poorly responsive, and had vomited. On arrival at the emergency room, an electrocardiogram showed sinus tachycardia. He responded to supportive treatment, and was discharged 3 days later in good condition. Geller et al. (1991) reported the case of a 3-year-old boy who ingested 15- 30 mL of nail tip glue remover containing 95% acetonitrile, and Kurt et al. 

Aliphatic Nitriles 25 (1991) reported the case of a 2-year-old girl who had ingested 5-10 mL artificial nail glue remover containing 84% acetonitrile. Both children were asymptomatic for 11-14 h after the ingestions. They then became restless and vomited and the girl became comatose with tachycardia. After treatment, both children recovered and were discharged within 2 days. 2.3.2.2. Experimental Studies Pozzani et al. (1959) exposed three male volunteers (ages 31-47 years) to acetonitrile at 40 ppm for 4 h in a 7,900-L chamber. Air was exhausted from the chamber at 1,400 L/min and chamber air temperature was kept below 76°F. A physician was available during the exposure period. Blood cyanide content was determined 19 days and 1 day prior to and immediately after the exposure. The thiocyanate content of 24-h urine samples was determined 19, 18, and 1 days before the test and immediately after. All subjects detected the odor of acetoni- trile during the first 2-3 h, after which some olfactory fatigue was experienced. The two older subjects reported no subjective symptoms during or after the 4-h inhalation period, and there was no appreciable increase in urinary thiocyanate and no detectable blood cyanide. The youngest subject reported no adverse sub- jective response during the inhalation period, but experienced slight chest tight- ness that evening. The following morning, he reported a cooling sensation in the lung, which persisted for 24 h and was similar to that experienced when menthol was inhaled. There was no detectable blood cyanide in this subject, but a slight increase in urinary thiocyanate was found. The two older subjects were tested one week later with acetonitrile at 80 ppm for 4 h. No subjective symptoms were reported before or during the exposure, and no blood cyanide was detected after exposure. The urinary thiocyanate value of one subject was higher immediately before inhalation than after, and the values for the other subject were constant. Finally, nine days after the 80-ppm exposure, the same two subjects were tested with acetonitrile at 160 ppm for 4 h. One subject reported a slight transitory flushing of the face 2 h after inhalation and slight bronchial tightness 5 h later, which resolved overnight. Blood cyanide and urinary thiocyanate values were similar before and after exposure, and both subjects said that they would have no hesitation about being exposed at 160 ppm for another 4-h period. 2.3.3. Developmental and Reproductive Toxicity Developmental and reproductive studies regarding acute human exposure to acetonitrile were not available. 2.3.4. Genotoxicity Genotoxicity studies regarding acute human exposure to acetonitrile were not available. 

26 Acute Exposure Guideline Levels 2.3.5. Carcinogenicity Carcinogenicity studies regarding human exposure to acetonitrile were not available. 2.3.6. Summary Case reports of acetonitrile toxicity exist; however, exposure concentra- tions and durations were not available. Signs and symptoms from inhalation, dermal, and oral exposure to acetonitrile are similar and include chest pain, chest tightness, nausea, vomiting, tachycardia, short and shallow respiration, head- ache, restlessness, and seizures. Effects are primarily due to the metabolism of acetonitrile to cyanide, and blood cyanide and thiocyanate concentrations are increased after acute poisoning. Human case reports have indicated that the on- set of symptoms is delayed for several hours after exposure (in contrast to the rapid toxicity of cyanide itself); this delay is consistent with the metabolism that must occur to release the cyanide moiety. Only one controlled experiment of the acute inhalation toxicity of acetonitrile was available, and no information about the potential human developmental and reproductive toxicity, genotoxicity or carcinogenicity was found. 2.4. Animal Toxicity Data 2.4.1. Acute Lethality 2.4.1.1. Rats Groups of 10 male Sprague-Dawley rats were exposed to acetonitrile at 10,100, 13,600, 19,700, or 22,200 ppm for 4 h in a 20-L glass exposure cham- ber, followed by a 14-day observation period (Monsanto 1986). Metered air was bubbled through a heated (80°C) bubbler of the acetonitrile. This stream was diluted with air at 15 L/min prior to entering the exposure chamber. The acetoni- trile exposure concentration was monitored continuously over the 4-h period using a gas analyzer, and the concentration of acetonitrile vapor was determined with a calibration curve. Animals were observed hourly during exposure and daily thereafter. Rats exposed at 10,100 ppm had hemorrhagic lungs, and rats exposed at higher concentrations had hemorrhagic lungs and corneal opacity. Mortality was 0/10 at 10,100 ppm, 1/10 at 13,600 ppm, 3/10 at 19,700 ppm, and 8/10 at 22,200 ppm. An LC50 of 19,950 ppm and an LC01 of 8,421 ppm were calculated. Groups of 10 young adult male ChR-CD rats were exposed to acetonitrile (concentrations not specified) for 4 h and observed for up to 14 days (DuPont 1968). The test sample was uniformly metered by a syringe drive into a stainless steel T-tube whose internal temperature was above the boiling point of the ace- tonitrile. A metered stream of air passing through the T-tube carried the vapors 

Aliphatic Nitriles 27 to the exposure chamber where the atmosphere was analyzed every half-hour by gas chromatography. Irregular respiration, hyperemia, incoordination, and face pawing were observed at sublethal concentrations during exposure, and irregular respiration, hyperemia followed by pale ears, face pawing, incoordination, and unresponsiveness were observed at lethal concentrations during exposure. Mild to severe weight loss for 1-3 days, followed by normal weight gain, was ob- served after the exposure period at sublethal concentrations. Severe weight loss for 1-3 days, followed by normal weight gain, was observed after the exposure period at lethal concentrations. Deaths occurred from 3 h during exposure through 24-h post-exposure. An LC50 of 17,100 ppm (14,600-20,000 ppm) was calculated. No other experimental details were reported. Haguenoer et al. (1975) exposed three rats to acetonitrile at 25,000 ppm; all rats died within 30 min after the start of exposure after exhibiting difficult breathing and cyanosis. Another group of three rats was exposed to acetonitrile at 2,800 ppm for 2 h/day for up to 5 days. All rats had labored breathing, tempo- rary anuria, and diarrhea. After the third exposure, one rat died with lung and brain hemorrhage. After the fourth exposure, the remaining two rats had paraly- sis and decreased urinary excretion. One rat died at the start of the fifth exposure and the other died 2 h after the fifth exposure was completed. Both rats lost 45% of their body weight over the 5-day period. Groups of 30 rats were exposed to acetonitrile at 4,000, 8,000, or 16,000 ppm for 4 h (UCC 1965). Mortality was 10% at 4,000 ppm, 33% at 8,000 ppm, and 57% at 16,000 ppm. No other details were available. Pozzani et al. (1959) exposed groups of 12 male and 12 female Carworth Farms-Nelson rats to accurately metered acetonitrile vapor for 4- or 8-h periods at concentrations of 1,000 (8 h only), 2,000 (8 h only), 4,000, 8,000, 16,000, or 32,000 ppm. Prostration, usually followed by convulsive seizures, preceded death, and necropsy of decedents showed moderate to marked pulmonary hem- orrhage or congestion. Some of the surviving animals also had these pulmonary effects at necropsy, but the effects were of less marked severity (described by as less than “moderate to marked pulmonary hemorrhage or congestion”). Mortali- ty data and calculated LC50 values are presented in Table 1-4. The investigators also reported that 0/6 rats died when exposed to acetonitrile at 53,000 for 15 min, whereas 3/6 rats died when exposed at this concentration for 30 min. A 13-week repeated exposure study (NTP 1996) described both lethal and nonlethal effects in rats; this study is described in Section 2.4.2.1. 2.4.1.2. Mice Groups of 10 male CD-1 mice were exposed to five or six concentrations of acetonitrile ranging from 500-5,000 ppm for 60 min and observed for 14 days (Willhite 1981). Actual individual group exposure concentrations were not re- ported. Acetonitrile was mixed with a stream of dehumidified air (10 L/min) and 

28 Acute Exposure Guideline Levels TABLE 1-4 Mortality in Rats Exposed to Acetonitrile for 8 and 4 Hours Concentration 8h 4h (ppm) Male Female Male Female 1,000 0/12 0/12 – – 2,000 0/12 1/12 – – 4,000 1/12 1/12 0/12 0/12 8,000 6/12 1/12 3/12 0/12 16,000 12/12 9/12 3/12 6/12 32,000 12/12 12/12 12/12 12/12 LC50 7,551 12,435 16,000 16,000 (5,975 to 9,542) (11,036 to 14,011) (12,450 to 20,5662) (13,037 to 19,636) Source: Pozzani et al. 1959. Reprinted with permission; copyright 1959, Journal of Oc- cupational and Environmental Medicine. delivered to a single pass 45-L glass inhalation chamber. Samples were collected every 5 min using a gas-tight syringe and were analyzed by gas chromatog- raphy. The mice exhibited dyspnea, tachypnea, gasping, tremors, convulsions, and corneal opacity 30-300 min following initial contact with acetonitrile. All mice exposed at 5,000 ppm died within 180 min of initial exposure and delayed deaths were observed for up to 3 days after exposure at lower (unspecified) con- centrations. The livers of exposed mice were bright red compared with controls. An LC50 of 2,693 ppm (1,955-4,247 ppm) was calculated. Groups of five male and five female Crl:CD-1 (ICR) BR mice were ex- posed to acetonitrile (>99.9%) vapor for 4 h via whole-body exposure methods (MPI 1998). Mean analytic concentrations determined by infrared spectrometer analysis were 3,039, 5,000, 4,218, and 3,568 ppm (Groups 1-4, respectively). Combined sex mortalities were 20, 80, 90, and 50%, respectively. All mortalities occurred on the day of exposure, except for a single male that died in the low- exposure group on post-exposure day 1. Clinical signs observed during the ex- posure and up to 4-h post-exposure included death, decreased activity, abnormal gait, loss of righting reflex, slow respiration, labored breathing, rapid respira- tion, gasping, cold-to-the-touch splayed limbs, leaning to the right, and yellow body surface staining. Surviving animals from Groups 2-4 were judged normal by study day 2. Clinical signs observed during the 14-day observation period for animals exposed at 3,039 ppm included death, decreased activity, and decreased defecation; survivors in this group were judged normal by study day 5. At nec- ropsy, no test article-related macroscopic findings were observed in male or female mice. All tissues were considered to be within normal limits. A 4 h LC50 of was calculated to be 3,587 ppm, with 95% confidence limits of 2,938-4,039 ppm. A 13-week repeated exposure study (NTP 1996) described both lethal and nonlethal effects in mice; this study is described in Section 2.4.2.2. 

Aliphatic Nitriles 29 The oral LD50 for acetonitrile was estimated to be 269 mg/kg in male ddY mice (Tanii and Hashimoto 1984). An intraperitoneal LD50 for acetonitrile of 521 mg/kg was reported for mice (Lewis 1996). No further information was available. 2.4.1.3. Rabbits Pozzani et al. (1959) exposed groups of four male rabbits to accurately metered acetonitrile vapor for 4 h at concentrations of 1,000, 2,000, or 4,000 ppm. Prostration, usually followed by convulsive seizures, preceded death, and necropsy of decedents showed moderate to marked pulmonary hemorrhage or congestion. Some of the surviving animals had these pulmonary effects at nec- ropsy, but the effects were of less marked severity. No rabbits died at 1,000 or 2,000 ppm, and all four rabbits died at 4,000 ppm. An LC50 of 2,828 ppm was calculated. 2.4.1.4. Guinea Pigs Pozzani et al. (1959) exposed groups of six guinea pigs to accurately me- tered acetonitrile vapor for 4 h at concentrations of 4,000, 8,000, or 16,000 ppm. Both males and females were used, but were not equally distributed between groups. Prostration, usually followed by convulsive seizures, preceded death, and necropsy of decedents showed moderate to marked pulmonary hemorrhage or congestion. Some of the surviving animals had these pulmonary effects at necropsy, but the effects were of less marked severity. No guinea pigs died at 4,000 ppm; and all six guinea pigs in both the 8,000- and 16,000-ppm groups died. An LC50 of 5,655 ppm was calculated. 2.4.1.5. Dogs Pozzani et al. (1959) also exposed groups of male dogs to accurately me- tered acetonitrile vapor for 4 h at concentrations of 2,000, 8,000, 16,000, or 32,000 ppm. Prostration, usually followed by convulsive seizures, preceded death, and necropsy of decedents showed moderate to marked pulmonary hemorrhage or congestion. Some of the surviving animals also showed these pulmonary effects, but the effects were of less marked severity. Mortality was 0/2 at 2,000 ppm, 0/1 at 8,000 ppm, 3/3 at 16,000 ppm, and 1/1 at 32,000 ppm. 2.4.2. Nonlethal Toxicity 2.4.2.1. Rats Nonlethal effects in rats were reported by Pozzani et al. (1959). The proto- col the study is described in Section 2.4.1.1, and nonlethal effects were de- scribed as less than marked pulmonary congestion or hemorrhage. 

30 Acute Exposure Guideline Levels Five male and five female rats were exposed to acetonitrile at 4,760 ppm in a 200-L glass chamber for 1 h and observed for 14 days (Northview Pacific Labs 1989). One female lost weight, but all other rats gained weight during the follow-up period. No rats died, and there were no gross abnormalities observed at necropsy. No further experimental details were presented. In a repeated-exposure study, groups of 15 male and 15 female Carworth Farms-Wistar rats were exposed to acetonitrile at 0, 166, 330, or 655 ppm for 7 h/day, 5 days/week for 90 days (Pozzani et al. 1959). Air was drawn from the 200-L exposure chamber at a rate of 125 L/min, and the acetonitrile concentra- tions were measured four times daily. There were no treatment-related deaths, or effects on body, liver, or kidney weights. Rats in the 166-ppm group had histo- cyte clumps in the alveoli (1/28), and those in the 330-ppm group exhibited bronchitis, pneumonia, and atelectasis (3/26). In rats exposed at 655 ppm, alveo- lar capillary congestion and focal edema (10/27, p < 0.001), accompanied by bronchial inflammation, desquamation, and hypersecretion of mucous, were observed. Tubular cloudy swelling of the kidneys (8/27, p < 0.005) and central cloudy swelling of the livers (7/27, p < 0.04) were also found at 655 ppm. No other treatment-related effects were noted. In another repeated-exposure study, groups of 10 male and 10 female F344/N rats were exposed to acetonitrile at 0, 100, 200, 400, 800, or 1,600 ppm for 6 h/day, 5 days/week for 13 weeks (NTP 1996). Vapor was generated by pumping liquid acetonitrile from a reservoir into a stainless steel vaporizer heat- ed to 177°F. The acetonitrile vapor was then mixed with filtered air, and the mixture drawn into a stainless steel distribution manifold, diluted to desired con- centrations by adjusting compressed air pressure to the vacuum pumps, and de- livered to the 1.7-m3 exposure chambers. Chamber concentrations were moni- tored by gas chromatography, and calibration was accomplished by acquiring grab samples from each exposure chamber. The samples were analyzed against gravimetrically prepared standards using an off-line gas chromatograph. The time required to achieve 90% of target concentrations after the start of vapor generation was 15-17 min, and the time required for chamber concentration to decay to 10% of target after vapor generation was terminated was 12-14 min. In the 800-ppm group, one male died during the first week of exposure. In the 1,600-ppm group, death occurred in six males (four during week 1, one during week 2, and one during week 4) and three females (one during week 1 and two during week 2). Hypoactivity and ruffled fur were observed during the first week of the study in males exposed at 800 ppm and in both sexes exposed at 1,600 ppm. Additionally, ataxia, abnormal posture, and clonic convulsions were noted in 1,600-ppm males that died during week 1. Decreased body weight gains were noted at 1,600 ppm, and depression of the myeloid system and mild hypo- thyroidism were also noted at 1,600 ppm. Gross necropsy findings were limited to animals that died early and included red, dark, and mottled lungs, and red foci on the brain. Increased absolute and/or relative kidney, heart, and liver weights and decreased thymus weights were noted at 800 and 1,600 ppm. No effects were reported at concentrations of 400 ppm or lower. 

Aliphatic Nitriles 31 2.4.2.2. Mice In a repeated-exposure study, groups of 10 male and 10 female B6C3F1 mice were exposed to acetonitrile at 0, 100, 200, 400, 800, or 1,600 ppm for 6 h/day, 5 days/week for 13 weeks (NTP 1996). The vapor generation and expo- sure monitoring were the same to those described for tests in rats in Section 2.4.2.1. All mice in the 1,600-ppm group died during the first 3 weeks of the study, and one female and one male exposed at 400 ppm and four females ex- posed at 800 ppm died before the end of the study. Hypoactivity and hunched rigid posture were observed during the first week of the study in the 800- and 1,600-ppm groups. Decreased body weight gains were noted only in 800-ppm males. In males exposed at 200 ppm or higher, an increase in absolute liver weights was found; relative liver weights were increased in males in all expo- sure groups. In females, absolute liver weight was increased at 800 ppm, and relative liver weight was increased at concentrations of 400 ppm or higher. In males exposed at 400 ppm or higher and in females exposed at 200 ppm or higher, areas of focal epithelial hyperplasia and ulceration were observed in the forestomachs. An increased incidence of cytoplasmic vacuolization was found in livers of males and females exposed to acetonitrile at 400 and 800 ppm. A lack of fatty degenerative change was observed in the X-zone of the adrenal cortex of females exposed at 800 and 1,600 ppm. No effects were reported in mice ex- posed at 100 ppm. 2.4.2.3. Dogs Pozzani et al. (1959) exposed three male hybrid dogs to acetonicrile at 350 ppm for 7 h/day, 5 days/week for 91 days. The inhalation chamber was a 7,900- L cube from which air was exhausted at 1,400 L/min. Liquid acetonitrile was delivered at a constant rate from a dual syringe feeder into a heated Pyrex evap- orator. The vapor was then introduced into the chamber under slight negative pressure. Daily inhalation concentrations were estimated from the amount of liquid acetonitrile consumed and the mean daily dilution airflow. The lack of animal housing facilities precluded an air control group. Decreased body weights were on days 3-72. Hematocrit and hemoglobin values were decreased during the first 5 weeks of the study, but returned to normal by the end of the 91-day inhalation period. Focal emphysema and alveolar septa proliferation were found at necropsy. 2.4.2.4. Monkeys Pozzani et al. (1959) exposed three adult male Rhesus monkeys to acetoni- trile at 350 ppm for 7 h/day, 5 days/week for 91 days. The exposure conditions were that same as those used in the tests in dogs described in Section 2.4.2.3. Bronchitis was noted during the 91-day inhalation period. Necropsy revealed 

32 Acute Exposure Guideline Levels moderate hemorrhage of superior and inferior sagittal sinuses of the brain; how- ever, this effect was considered an artifact of postmortem alteration due to tissue handling procedures. Pozzani et al. (1959) also reported that one Rhesus monkey exposed to ac- etonitrile at 2,510 ppm for 7 h/day appeared normal after the first day of inhala- tion; however, this animal exhibited poor coordination followed by prostration and labored breathing during the second exposure. This monkey died a few hours later. In another experiment, Pozzani et al. (1959) exposed two monkeys at 660 ppm for 7 h/day. Poor coordination was observed in both monkeys during the second week of exposure. One animal vomited before death on day 23 of exposure. 2.4.3. Developmental and Reproductive Toxicity In a developmental toxicity study (Mast et al. 1994), Sprague-Dawley rats were exposed to acetonitrile at 0, 100, 400, or 1,200 ppm for 6 h/day, 7 days/week. Each group consisted of 10 nonpregnant females (comparison group), 10 positively mated females for a distribution study evaluating maternal blood for acetonitrile and cyanide, and 33 positively mated females for evaluat- ing developmental toxicity. Rats were exposed for 14 consecutive days (on days 6-19 of gestation for pregnant animals). The vapor generation and exposure sys- tems were similar to those described for the 13-week rat and mouse studies (NTP 1996) described in section 2.4.2.1. In the 400-ppm group, a single dam died on gestational day 14 due to spontaneous cerebral hemorrhage; the study authors did not report any signs of toxicity or note any other adverse findings on necropsy in this animal. In the 1,200-ppm group, three animals were killed in a moribund state (one nonpregnant rat and two dams); they had severe clinical signs of toxicity (hypoactivity and emaciation). Therefore, it appears that the single death in the 400-ppm group was unlikely to be due to acetonitrile expo- sure. No treatment-related effects on body weights or reproductive indices at any treatment level were observed, and there were no significant increases in fetal malformations or variations. Measurement of acetonitrile and cyanide concen- trations in maternal blood showed that the acetonitrile concentration in blood increased with the exposure concentration. Cyanide was detected only in the blood of animals in the 1,200-ppm group. Willhite (1983) exposed groups of 6-12 pregnant Syrian Golden hamsters to acetonitrile at 0, 1,800, 3,800, 5,000, or 8,000 ppm for 1 h on day 8 of gesta- tion. Acetonitrile was mixed with a stream of dehumidified air at a rate of 10 L/min and delivered to a 45-L glass inhalation chamber. Chamber concentra- tions were measured by gas chromatography. No maternal or offspring effects were found at 1,800 ppm. One dam exposed at 3,800 ppm had dyspnea, tremors, hypersalivation, ataxia, and hypothermia at the end of the exposure period and died 3 h post-exposure. No other maternal effects and no offspring effects were found at 3,800 ppm. All dams exposed at 5,000 ppm exhibited excessive saliva- 

Aliphatic Nitriles 33 tion, and one dam had dyspnea, hypothermia, and tremors at the conclusion of exposure; this animal died 5 h later. Six abnormal fetuses were found in two litters from the 5,000-ppm group; malformations included exencephalyencepha- locoele and rib fusions. Four dams exposed at 8,000 ppm had respiratory diffi- culty, lethargy, ataxia, hypothermia, ocular and nasal irritation, and gasping. Three of these hamsters developed tremors followed by deep coma, and died within 90 min after exposure. The offspring from five of nine surviving litters of the 8,000-ppm group had severe axial skeletal dysraphic disorders, and average fetal body weight was decreased compared with air controls. Overall, there was an increase in the number of abnormal fetuses in the 5,000- and 8,000-ppm groups compared with controls. Although lethality data are not available to compare the sensitivity of pregnant and nonpregnant hamsters, increased sensi- tivity to acetonitrile during pregnancy is possible. Saillenfait et al. (1993) exposed groups of 20 pregnant Sprague-Dawley rats to acetonitrile at nominal concentrations of 0, 900, 1,200, 1,500, or 1,800 ppm (analytic concentrations were 0, 1,000 ± 53.7, 1,287 ± 66.4, 1,592 ± 120.4, or 1,827 ± 138.5 ppm, respectively) for 6 h/day on days 6-20 of gestation. Expo- sure was conducted in a 200-L stainless steel dynamic flow inhalation chamber. The chamber temperature was set at 23 ± 2°C and the relative humidity at 50 ± 5%. Vapors were generated by bubbling air through a flask containing the test compound and were mixed with filtered room air to achieve the desired concen- tration. The nominal concentrations were calculated from the ratio of the amount of test compound vaporized to the total chamber air flow during the exposure period. Analytic concentrations were determined once every hour during each 6- h exposure period using gas-liquid chromatography. Eight of 20 exposed fe- males died (time-to-death not reported) in the 1,800 ppm group, and no other maternal deaths were observed. Maternal absolute weight gain was decreased (p < 0.05) to 60% of control values at 1,500 and 1,800 ppm. Increases (p < 0.01) in the mean percentage of nonsurviving implants and early embryonic resorptions were found in the 1,800-ppm group, and were accompanied by a decrease in mean number of live fetuses per litter. One litter was completely resorbed in a dam exposed at 1,800 ppm. No other treatment-related maternal or fetal effects were observed. Although this study involved repeated exposures, fetal death is relevant to AEGL values because fetal toxicity could result from a single expo- sure. Results of an oral exposure study in pregnant rats show that acetonitrile can induce fetal toxicity after a single exposure (Saillenfait and Sabaté 2000). Pregnant Sprague-Dawley rats were administered a single oral dose of acetoni- trile (2,000 mg/kg) on gestational day 10, and fetuses were examined for mal- formations on gestational day 12. Embryo viability was not affected, but abnor- mal development, including “overall poor and abnormal development” and misdirected allantois and trunk and/or caudal extremities were observed. Johannsen et al. (1986) administered aqueous solutions of acetonitrile at concentrations of 0, 125, 190, or 275 mg/kg by gavage to pregnant rats on days 6-19 of gestation. Maternal body weights were decreased and death occurred in 

34 Acute Exposure Guideline Levels high-dose dams; no other maternal effects were found at lower concentrations. Increases in early resorptions and post-implantation losses were found only in the high-dose group, and no teratogenic effects were found in any dose group. Groups of 25 pregnant New Zealand white rabbits were administered ace- tonitrile at 0, 2.0, 15.0, or 30.0 mg/kg/day by gavage on days 6-18 of gestation (Argus Research Labs 1984). Rabbits in the high-dose group had decreased body weight gain and anorexia, and death occurred in five animals. Body weight was also decreased in the dames exposed at 15 mg/kg/day. A decrease (p = 0.011) in the average number of live fetuses in high-dose group was found, but no other fetal effects were noted in any dose group. 2.4.4. Genotoxicity Acetonitrile did not induce mutations in Salmonella typhimurium (Mor- telmans et al. 1986; Schlegelmilch et al. 1988; NTP 1996) or L5178Y mouse lymphoma cells with or without metabolic activation (S9). A weakly positive response was obtained in a sister-chromatid exchange assay in cultured Chinese hamster ovary cells only in the presence of S9 (NTP 1996). In another study, slight increases in sister-chromatid exchange frequency were found in cultured Chinese hamster ovary cells without S9 and slight increases in chromosomal aberrations occurred with S9 (Galloway et al. 1987). There was an increase in micronucleated normochromatic erythrocytes in peripheral blood samples from male mice exposed to acetonitrile for 13 weeks; however, the frequency was not affected in female mice treated similarly (NTP 1996). There was no increase in unscheduled DNA synthesis in rat hepatocytes in vivo or in vitro. Sex chromo- some aneuploidy was induced in the oocytes of female Drosophila melanogaster fed acetonitrile as larvae or as adults (Osgood et al. 1991), and acetonitrile in- duced aneuploidy, but no point mutations or recombination, in Sacchromyces cerevisiae (Zimmermann et al. 1985). 2.4.5. Carcinogenicity In a carcinogenicity study, groups of 56 male and 56 female F344/N rats were exposed to acetonitrile at 0, 100, 200, or 400 ppm for 6 h/day, 5 days/week for 2 years (NTP 1996). The vapor was generated by pumping liquid acetonitrile from a reservoir to a stainless steel vaporizer heated at 200°F. The acetonitrile vapor was then mixed with filtered air, and the mixture drawn into a stainless steel distribution manifold, diluted to desired concentrations by adjusting com- pressed air pressure to the vacuum pumps, and delivered to the 1.7-m3 exposure chambers. Chamber concentrations were monitored by gas chromatography, and calibration was accomplished by acquiring grab samples from each exposure chamber. The samples were analyzed against gravimetrically prepared standards using an off-line gas chromatograph. The time to achieve 90% of target concen- trations after the start of vapor generation was 10-15 min, and the time for 

Aliphatic Nitriles 35 chamber concentration to decay to 10% of target after vapor generation was terminated was 14-17 min. No treatment-related effects on survival, mean body weights, organ weights, clinical signs, or hematological parameters were found. There was an increased incidence of hepatocellular adenoma (3/48), hepatocel- lular carcinoma (3/48), and hepatocellular adenoma or carcinoma combined (5/48) in male rats exposed at 400 ppm compared with controls (one carcinoma). The incidences of hepatocellular adenoma and carcinoma were within the ranges found for historical controls. However, the incidence of the adenoma or carci- noma combined (10%) slightly exceeded the range of the historical controls (2- 8%). There were no exposure-related lesions in female rats. NTP concluded that there was equivocal evidence of carcinogenic activity in male F344/N rats based on marginally increased incidences of hepatocellular adenoma and carcinoma. There was no evidence of carcinogenic activity of acetonitrile in female rats exposed to acetonitrile at 100, 200, or 400 ppm. In a carcinogenicity study, groups of 60 male and 60 female B6C3F1 mice were exposed to acetonitrile at 0, 50, 100, or 200 ppm for 6 h/day, 5 days/week for 2 years (NTP 1996). The vapor generation and exposure systems were the same as those described above for the rat cancer bioassay. No treatment-related effects on survival, mean body weights, organ weights, clinical signs, or hema- tological parameters were found. There was a concentration-related increased incidence of squamous hyperplasia of the forestomach epithelium in all expo- sure groups. There were no treatment-related increases in the incidences of neo- plasms. NTP concluded that there was no evidence of carcinogenic activity of acetonitrile in male or female B6C3F1 mice exposed at 50, 100, or 200 ppm. 2.4.6. Summary Acetonitrile produces toxic effects consistent with those observed with cya- nide poisoning. Effects observed in experimental animals include labored breath- ing, dyspnea, hypoactivity, ataxia, abnormal posture, convulsions, and pulmonary histopathology. Prostration followed by seizures often precedes death. Both lethal and sublethal data indicate that mice, pregnant hamsters, guinea pigs, rabbits, dogs, and monkeys are more sensitive than rats to the effects of acetonitrile. Lethal effects of acetonitrile are summarized in Table 1-5 and sublethal effects are sum- marized in Table 1-6. There was a significant and concentration-dependent increase in the number of abnormal fetuses in hamsters exposed to acetonitrile via inhalation. In rats and rabbits, acetonitrile was not toxic to fetuses at concentrations below those causing maternal toxicity; however, fetal death was observed under exposure conditions that produced maternal death. Although the developmental studies involved re- peated exposures, fetal death is relevant AEGL values because fetal toxicity could result from a single exposure. Acetonitrile was not active in gene-mutation assays of bacteria or cultured mammalian cells; however, it was positive in assays 

36 TABLE 1-5 Summary of Lethal Effects of Acetonitrile in Animals Species Concentration (ppm) Exposure Duration Effect Reference Acute exposure Rat 53,000 15 min No death Pozzani et al. 1959 Rat 53,000 30 min 50% mortality (3/6) Pozzani et al. 1959 Rat 25,000 30 min 100% mortality (3/3) Haguenoer et al. 1975 Rat 4,000 4h 10% mortality (3/30) UCC 1965 Rat 8,000 4h 33% mortality (10/30) UCC 1965 Rat 16,000 4h LC50 Pozzani et al. 1959 Rat 19,500 4h LC50 Monsanto 1986 Rat 17,100 4h LC50 DuPont 1968 Rat 16,000 4h 57% mortality (17/30) UCC 1965 Rat (male) 7,551 8h LC50 Pozzani et al. 1959 Rat (female) 12,435 8h LC50 Pozzani et al. 1959 Mouse 2,693 1h LC50 Willhite 1981 Mouse 5,000 1h 100% mortality (10/10) Willhite 1981 Mouse 3,587 4h LC50 MPI 1998 Hamster (pregnant) 1,800 1h No maternal death Willhite 1983 Hamster (pregnant) 3,800 1h No embryo lethality Willhite 1983 Hamster (pregnant) 3,800 1h 16% mortality (1/6) Willhite 1983 Rabbit 4,000 4h LC50 Pozzani et al. 1959 Guinea pig 5,655 4h LC50 Pozzani et al. 1959 Dog 16,000 4h 100% mortality (3/3) Pozzani et al. 1959 Dog 32,000 4h 100% mortality (1/1) Pozzani et al. 1959 

Repeated exposure Mouse (female) 200 6 h/d, 5 d/wk, 13 wk No death NTP 1996 Mouse (male) 400 6 h/d, 5 d/wk, 13 wk No death NTP 1996 Rat (male) 400 6 h/d, 5 d/wk, 13 wk No death NTP 1996 Rat (pregnant and 400 6 h/d, 7 d/wk, gestational days 6-19 No deatha Mast et al. 1994 non-pregnant females) Mouse (female) 400 6 h/d, 5 d/wk, 13 wk 10% mortality (1/10)b NTP 1996 Rat (female) 800 6 h/d, 5 d/wk, 13 wk No death NTP 1996 Rat (male) 800 6 h/d, 5 d/wk, 13 wk 10% mortality (1/10)c NTP 1996 d Mouse (male) 800 6 h/d, 5 d/wk, 13 wk 10% mortality (1/10) NTP 1996 Rat (female) 1,200 6 h/d, 7 d/wk, 14 exposures 10% mortality (1/10)e Mast et al. 1994 (mimicking gestational days 6-19) Rat (pregnant) 1,200 6 h/d, 7 d/wk, gestational days 6-19 6% mortality (2/33) in damsf; no Mast et al. 1994 embryo lethality Rat (pregnant) 1,500 6 h/d, gestational days 6-20 No maternal death or embryo lethality Saillenfait et al. 1993 Rat (female) 1,600 6 h/d, 5 d/wk, 13 wk 30% mortality (3/10)g NTP 1996 Rat (pregnant) 1,800 6 h/d, gestational days 6-20 40% mortality (8/20) in dams; Saillenfait et al. 1993 embryo lethalityh a One dam died on gestational day 14 due to spontaneous cerebral hemorrhage; this effect was probably unrelated to acetonitrile exposure. b Death occurred during week 2. c Death occurred during week 1. d Death occurred sometime during weeks 6-13. e Death occurred on gestational day 8. f Deaths occurred on gestational days 15 and 19. g Deaths occurred during weeks 1-2. h Increase in mean percentage of nonsurviving implants and early embryonic resorptions; decrease in mean number of live fetuses per litter; total resorption of one litter. Time-to-death of dams was not reported. 37 

38 TABLE 1-6 Summary of Sublethal Effects of Acetonitrile in Animals Species Concentration (ppm) Exposure Duration Effect Reference Acute exposure Rat 4,000 4h Less than marked pulmonary congestion or hemorrhage. Pozzani et al. 1959 Rat 1,000 8h Less than marked pulmonary congestion or hemorrhage. Pozzani et al. 1959 Rabbit 2,000 4h Less than marked pulmonary congestion or hemorrhage. Pozzani et al. 1959 Guinea pig 4,000 4h Less than marked pulmonary congestion or hemorrhage. Pozzani et al. 1959 Dog 2,000 4h Less than marked pulmonary congestion or hemorrhage. Pozzani et al. 1959 Monkey 2,510 7h No effect. Pozzani et al. 1959 Repeated exposure Rat 2,800 2 h, up to 5 d Labored breathing, temporary anuria, diarrhea. Haguenoer et al. 1975 Rat 166 7 h/d, 5 d/wk, 90 d Histiocyte clumps in alveoli. Pozzani et al. 1959 Rat 330 7 h/d, 5 d/wk, 90 d Bronchitis, pneumonia, atelectasis. Pozzani et al. 1959 Rat 655 7 h/d, 5 d/wk, 90 d Bronchial inflammation, desquammation, mucous hypersecretion, Pozzani et al. 1959 hepatic and renal lesions. Rat 400 6 h/d, 5 d/wk, 90 d No effect. NTP 1996 Rat 800 6 h/d, 5 d/wk, 90 d Hypoactivity, ruffled fur (wk 1), death (1/10 male), NTP 1996 increased organ weights. Rat 1,600 6 h/d, 5 d/wk, 90 d Hypoactivity, ruffled fur (wk 1), ataxia, abnormal posture, NTP 1996 convulsions, decreased body weight, death, increased organ weights, gross lung and brain lesions. Mouse 100 6 h/d, 5 d/wk, 90 d No effect. NTP 1996 Mouse 200 6 h/d, 5 d/wk, 90 d Increased liver weight; forestomach pathology. NTP 1996 Mouse 400 6 h/d, 5 d/wk, 90 d Increased liver weight, forestomach pathology, increased NTP 1996 cytoplasmic vacuolization of liver, death. 

Mouse 800; 1,600 6 h/d, 5 d/wk, 90 d Hypoactivity, hunched rigid posture, decreased body NTP 1996 weight gain (in 800-ppm group only), increased liver weight, forestomach pathology, increased cytoplasmic vacuolization of liver, death. Dog 350 7 h/d, 5 d/wk, 90 d Transitory decreases in body weight, transitory decreases Pozzani et al. 1959 in hemoglobin and hematocrit. Monkey 350 7 h/d, 5 d/wk, 90 d Bronchitis, moderate brain sinus hemorrhage. Pozzani et al. 1959 Monkey 2,510 7 h/d, 2 d Poor coordination, labored breathing, prostration, death. Pozzani et al. 1959 39 

40 Acute Exposure Guideline Levels designed to detect chromosome aberrations. There was equivocal evidence of car- cinogenic activity in male F344/N rats based on marginally increased incidences of hepatocellular adenoma and carcinoma. There was no evidence of carcinogenic activity of acetonitrile in female F344/N rats or in male or female B6C3F1 mice. 2.5. Data Analysis for AEGL-1 2.5.1. Human Data Relevant to AEGL-1 Pozzani et al. (1959) studied three male volunteers (ages 31-47) who in- haled acetonitrile at 40 ppm for 4 h. The two older subjects reported no subjec- tive symptoms during or after the inhalation period. The youngest subject re- ported no adverse subjective response during exposure, but experienced slight chest tightness that evening. The following morning, he reported a cooling sen- sation in the lungs, which persisted for 24 h and was described as being similar to that experienced when menthol was inhaled. The two older subjects were ex- posed 1 week later to acetonitrile at 80 ppm for 4 h; no symptoms were reported. Nine days after the 80-ppm exposure, the same two subjects were exposed at 160 ppm for 4 h. One subject reported a slight transitory flushing of the face 2 h after inhalation and slight bronchial tightness 5 h later, which resolved over- night. 2.5.2. Animal Data Relevant to AEGL-1 Effects observed in experimental animals exposed to acetonitrile by inhala- tion are generally no-effect levels or more severe than those defined by AEGL-1. 2.5.3. Derivation of AEGL-1 Values The slight chest tightness and cooling sensation in the lungs reported by one of three male volunteers exposed to acetonitrile at 40 ppm for 4 h (Pozzani et al. 1959) was selected as the basis for AEGL-1 values. An interspecies uncer- tainty factor of 1 was applied because the study involved humans. An intraspe- cies uncertainty factor of 1 was applied, because the mild effects are considered to have occurred in a sensitive subject since no symptoms were reported by two other subjects exposed at the same concentration or at a higher concentration of 80 ppm for 4 h. A modifying factor of 3 was applied to account for the sparse database. The resulting 4-h AEGL value of 13 ppm was held constant across the 10-, 30-min, and 1-h durations because no human data exist for periods of less than 4 h; thus, time scaling to shorter durations could yield values eliciting symptoms above those defined by AEGL-1. An 8-h AEGL-1 value was not de- rived because 13 ppm is essentially equal to the 8-h AEGL-2 value of 14 ppm. AEGL-1 values for acetonitrile are presented in Table 1-7, and the calculations are presented in Appendix B. 

Aliphatic Nitriles 41 TABLE 1-7 AEGL-1 Values for Acetonitrile 10 min 30 min 1h 4h 8h 13 ppm 13 ppm 13 ppm 13 ppm NRa (22 mg/m3) (22 mg/m3) (22 mg/m3) (22 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 2.6. Data Analysis for AEGL-2 2.6.1. Human Data Relevant to AEGL-2 Case reports describing human poisonings from acetonitrile leading to ef- fects consistent with the definition of AEGL-2 exist. However, due to the lack of reliable concentration and duration information, the data are not appropriate for deriving AEGL-2 values. 2.6.2. Animal Data Relevant to AEGL-2 Pulmonary congestion or hemorrhage, described by the investigators as less than “moderate to marked pulmonary hemorrhage or congestion” was ob- served in rats exposed to acetonitrile at 4,000 ppm for 4 h or at 1,000 ppm for 8 h, in rabbits exposed at 2,000 ppm for 4 h, in guinea pigs exposed at 4,000 ppm for 4 h, and in dogs exposed at 2,000 ppm for 4 h (Pozzani et al. 1959). These effects are considered to be AEGL-2 level effects. No-effect levels for these effects were not identified. 2.6.3. Derivation of AEGL-2 Values At nonlethal concentrations, AEGL-2 level effects, described as less than “moderate to marked pulmonary hemorrhage or congestion” were observed in rats (Pozzani et al. 1959). Since no-effect levels for AEGL-2 level effects were not identified, the data are not appropriate for deriving AEGL-2 values. There- fore, AEGL-2 values were estimated by dividing AEGL-3 values by 3. AEGL-2 values for acetonitrile are presented in Table 1-8. These values are considered protective because one of two human volun- teers exposed to acetonitrile at 160 ppm for 4 h experienced only a slight transi- tory flushing of the face 2 h after exposure and slight bronchial tightness 5 h later, which resolved overnight. Blood cyanide and urinary thiocyanate values were similar before and after exposure (Pozzani et al. 1959). Also, mice, the species most sensitive to acetonitrile, exhibited no effects after repeated expo- sure at 100 ppm (6 h/day, 5 days/week for 90 days), and had only increased liver weight and forestomach pathology when exposed at 200 ppm (6 h/day, 5 days/week for 90 days) (NTP 1996). 

42 Acute Exposure Guideline Levels TABLE 1-8 AEGL-2 Values for Acetonitrile 10 min 30 min 1h 4h 8h 80 ppm 80 ppm 50 ppm 21 ppm 14 ppm (130 mg/m3) (130 mg/m3) (84 mg/m3) (35 mg/m3) (24 mg/m3) 2.7. Data Analysis for AEGL-3 2.7.1. Human Data Relevant to AEGL-3 Human lethality data on acetonitrile were anecdotal and lacked reliable concentration and exposure duration information. Thus, those reports were not appropriate for establishing AEGL-3 values. 2.7.2. Animal Data Relevant to AEGL-3 Lethality studies of single exposures to acetonitrile are available for rats (Pozzani et al. 1959; DuPont 1968; UCC 1965; Haguenoer et al. 1975; Monsan- to 1986), mice (Willhite 1981), pregnant hamsters (Willhite 1983), rabbits, guinea pigs, and dogs (Pozzani et al. 1959). The lowest nonlethal-effect concen- tration observed for a single exposure was 1,800 ppm in pregnant hamsters ex- posed for 1 h (Willhite 1983). Deaths were reported in male and female rats ex- posed repeatedly to acetonitrile at 800 and 1,600 ppm, respectively, during the first week of exposure (NTP 1996). Gestational exposure studies provide addi- tional information on maternal death and embryo lethality. Maternal death and increased fetal resorptions were observed in rats exposed to acetonitrile at 1,800 for 6 h/day on gestational days 6-20, with a no-effect level for maternal and fetal death (resorptions) of 1,500 ppm for 6 h/day (Saillenfait et al. 1993). Maternal death, but not fetal death, was observed in rats exposed at 1,200 ppm for 6 h/day on gestational days 6-19 Mast et al. 1994). 2.7.3. Derivation of AEGL-3 Values The no-effect level for maternal and fetal mortality in pregnant rats ex- posed to acetonitrile at 1,500 ppm for 6 h/day on gestational days 6-20 (Saillen- fait et al. 1993) was the point of departure for deriving AEGL-3 values. Alt- hough the study involved repeated exposures, fetal death can occur during a narrow developmental window and does not necessarily require repeated expo- sures (Van Raaij et al. 2003). Therefore, the observation of increased fetal death following repeated gestational exposure is considered appropriate for derivation of AEGL-3 values. In addition, although the study identified no-effect levels for mortality that were below those observed in studies of single exposures of non- pregnant animals, it is possible that sensitivity to acetonitrile may increase dur- ing pregnancy. The point of departure of 1,500 ppm is supported by observa- 

Aliphatic Nitriles 43 tions of lethality in repeated exposure studies. In a 13-week study (6 h/day, 5 days/week), deaths were observed during the first week of exposure (number of days-to-death was not reported) in males exposed at 800 and 1,600 ppm and in females exposed at 1,600 ppm (NTP 1996). Two maternal deaths (on gestational days 15 and 19), but no fetal deaths, were observed in rats exposed at 1,200 ppm (6 h/day) on gestational days 6-19 (Mast et al. 1994). As noted above, embryon- ic death could occur after a single exposure. Thus, the 6-h no-effect level for fetal death of 1,200 ppm reported by Mast et al. (1994) supports the 6-h no- effect level for maternal and fetal lethality in the Saillenfait et al. (1993) study as the point of departure for deriving AEGL-3 values. An interspecies uncertainty factor of 10 was applied because no compara- ble data were identified for similar exposures (repeated inhalation exposure dur- ing gestation) in other species. An intraspecies uncertainty factor of 3 was ap- plied because studies of accidental and occupational exposures to hydrogen cyanide (the metabolically-liberated toxicant) indicate that there are individual differences in sensitivity to this chemical but that the differences are not ex- pected to exceed 3-fold (NRC 2002). Thus, the total uncertainty factor is 30. The concentration-time relationship for many irritant and systemically-acting vapors and gases may be described by the equation Cn × t = k (ten Berge et al. 1986). An empirical value for n of 1.6 was used (see Section 1.6 and Appendix A for how the value was determined). Time scaling was not performed for the 10-min AEGL-3 value, because of the uncertainty associated with extrapolating a point of departure based on a 6-h exposure duration to a 10-min value. The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value. AEGL-3 values for acetonitrile are presented in Table 1-9, and the calculations are presented in Ap- pendix B. 2.8. Summary of AEGLs 2.8.1. AEGL Values and Toxicity End Points AEGL values for acetonitrile are presented in Table 1-10. Slight chest tightness and cooling sensation in the lungs of one of three human volunteers was used as the basis for the AEGL-1 values. Data were inadequate for deriving AEGL-2 values, so estimates were made by dividing the AEGL-3 values by 3. The no-effect level for maternal and fetal lethality (increased resorptions) in rats was the basis for the AEGL-3 values. TABLE 1-9 AEGL-3 Values for Acetonitrile 10 min 30 min 1h 4h 8h 240 ppm 240 ppm 150 ppm 64 ppm 42 ppm (400 mg/m3) (400 mg/m3) (250 mg/m3) (110 mg/m3) (71 mg/m3) 

44 Acute Exposure Guideline Levels TABLE 1-10 AEGL Values for Acetonitrile Classification 10 min 30 min 1h 4h 8h AEGL-1 13 ppm 13 ppm 13 ppm 13 ppm NRa (nondisabling) (22 mg/m3) (22 mg/m3) (22 mg/m3) (22 mg/m3) AEGL-2 80 ppm 80 ppm 50 ppm 21 ppm 14 ppm (disabling) (130 mg/m3) (130 mg/m3) (84 mg/m3) (35 mg/m3) (24 mg/m3) AEGL-3 240 ppm 240 ppm 150 ppm 64 ppm 42 ppm (lethal) (400 mg/m3) (400 mg/m3) (250 mg/m3) (110 mg/m3) (71 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 2.8.2. Other Standards and Guidelines Exposure standards and guidelines for acetonitrile have been established by several organizations (see Table 1-11). The 30-min immediately dangerous to life or health value (IDLH) of 500 ppm is substantially higher than 10- and 30- min AEGL-3 values. The AEGL-3 values are based on a no-effect level for le- thality in rats, whereas the IDLH value is based on an acute inhalation study in humans showing that a 4-h exposure to acetonitrile at 160 ppm caused flushing and a feeling of chest constriction (Pozzani et al. 1959) and exposure at 500 ppm (duration not specified) caused irritation to the nose and throat. The recom- mended exposure limit of the National Institute for Occupational Safety and Health and the threshold limit value of the American Conference of Governmen- tal Industrial Hygienists of 20 ppm are based on human data showing that expo- sure to acetonitrile at 40 ppm for 4 h caused no effects in two volunteers and the sensation of cooling in the lungs and slight tightness of the chest in a third vol- unteer (Pozzani et al. 1959). The permissible exposure limit of the Occupational Safety and Health Administration of 40 ppm is based on the risks of organic cyanide poisoning and liver and respiratory tract injuries associated with expo- sure to acetonitrile. The German maximum workplace concentration for acetoni- trile was derived from a 2-year study in rats showing a dose-dependent increase in basophilic foci in the liver at concentrations of 100 ppm and higher. The basis of the Dutch maximal accepted concentration for acetonitrile was not found. 2.8.3. Data Adequacy and Research Needs Data were adequate for deriving AEGL-1 and AEGL-3 values for acetoni- trile, and AEGL-2 values were based on the AEGL-3 values. However, human data include just one experimental study and several anecdotal reports, so addi- tional supporting data for AEGL-1 values in humans or animals are needed. An- imal data are available for several species, with the vast majority of studies us- ing the rat. The animal data suggest that, as with other nitriles, the rat is more resistant to the toxic effects of acetonitrile than are other species. For other ni- triles, data suggest that this interspecies difference is due to the rate of metabolic 

Aliphatic Nitriles 45 cyanide liberation. However, no definitive data are available to explain this in- terspecies difference for acetonitrile. TABLE 1-11 Other Standards and Guidelines for Acetonitrile Exposure Duration Guideline 10 min 30 min 1h 4h 8h AEGL-1 13 ppm 13 ppm 13 ppm 13 ppm NRa (22 mg/m3) (22 mg/m3) (22 mg/m3) (22 mg/m3) AEGL-2 80 ppm 80 ppm 50 ppm 21 ppm 14 ppm (130 mg/m3) (130 mg/m3) (84 mg/m3) (35 mg/m3) (24 mg/m3) AEGL-3 240 ppm 240 ppm 150 ppm 64 ppm 42 ppm (400 mg/m3) (400 mg/m3) (250 mg/m3) (110 mg/m3) (71 mg/m3) IDLH (NIOSH)b 500 ppm – – – – (840 mg/m3) TLV-TWA – – – – 20 ppm (ACGIH®)c (34 mg/m3) REL-TWA – – – – 20 ppm (NIOSH)d (34 mg/m3) PEL-TWA – – – – 40 ppm (OSHA)e (70 mg/m3) MAK (Germany)f – – – – 20 ppm (34 mg/m3) MAC (The – – – – 40 ppm Netherlands)g (70 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. b IDLH (immediately dangerous to life or health, National Institute for Occupational Safety and Health) (NIOSH 1994) represents the maximum concentration from which one could escape within 30 min without any escape-impairing symptoms, or any irreversible health effects. The IDLH for acetonitrile is based on acute inhalation toxicity data in humans; comment is made in supporting documentation that this may be a conservative value. c TLV-TWA (threshold limit value—time-weighted average, American Conference of Governmental Industrial Hygienists) (ACGIH 2012) is the time-weighted average con- centration for a normal 8-h workday and a 40-h workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. d REL-TWA (recommended exposure limit—time-weighted average, National Institute for Occupational Safety and Health) (NIOSH 2011a) is defined analogous to the ACGIH TLV-TWA, but is for exposures of no more than 10 h/d, 40 h/wk. e PEL-TWA (permissible exposure limit—time-weighted average, Occupational Safety and Health Administration) (29 CFR 1910.1000 [1999]) is defined analogous to the ACGIH TLV-TWA, but is for exposures of no more than 8 h/d, 40 h/wk. f MAK (maximale argeitsplatzkonzentration [maximum workplace concentration], Deutsche Forschungsgemeinschaft [German Research Association]) (DFG 2012) is defined analogous to the ACGIH TLV- TWA. 

46 Acute Exposure Guideline Levels g MAC (maximaal aanvaaarde concentratie [maximal accepted concentration], Dutch Expert Committee for Occupational Standards, The Netherlands) (MSZW 2004), is defined analo- gous to the ACGIH TLV-TWA. 3. ISOBUTYRONITRILE 3.1. Summary Isobutyronitrile is a colorless liquid at ambient temperature and pressure. It has an almond-like odor and may cause irritation or burning of the eyes and skin. It is metabolized to cyanide in the body and signs of exposure may include weak- ness, headache, confusion, nausea, vomiting, convulsion, dilated pupils, weak pulse, shallow and gasping breathing, and cyanosis (EPA 1985). These same signs have been reported in humans exposed to hydrogen cyanide (Blanc et al. 1985). Data were insufficient to derive AEGL-1 values for isobutyronitrile. Data were also insufficient for deriving AEGL-2 values for isobutyronitrile, so the values were estimated by dividing AEGL-3 values by 3. The no-effect level for maternal mortality in pregnant rats exposed to iso- butyronitrile at 100 ppm for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993) was used as the point of departure for deriving AEGL-3 values for isobu- tyronitrile. Although the Saillenfait et al. (1993) study involved repeated expo- sures, the day on which the dams died and the number of exposures at the next highest dose (200 ppm) that preceded death were not reported; therefore, it is possible that the deaths could have resulted from a single exposure. The study identified no-effect levels for mortality that were lower than those observed in studies involving single exposures to nonpregnant animals; this might reflect a higher sensitivity of pregnant animals to the lethal effects of isobutyronitrile. Therefore, the no-effect level of 100 ppm for maternal toxicity (mortality) is considered appropriate for deriving AEGL-3 values. An intraspecies uncertainty factor of 3 was applied because studies of ac- cidental and occupational exposures to hydrogen cyanide (the metabolically- liberated toxicant) indicate that there are individual differences in sensitivity to this chemical but that the differences are not expected to exceed 3-fold (NRC 2002). An interspecies uncertainty factor of 10 was also applied because no comparable studies of similar exposures (repeated inhalation exposure during gestation) in other species were available. Thus, the total uncertainty factor is 30. Time scaling was performed using the equation Cn × t = k, where the expo- nent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). Data on isobutyronitrile were insufficient for deriving an empirical value for n. Therefore, default values of n = 3 to extrapolate to shorter durations (30 min, 1h, and 4 h) and n = 1 to extrapolate longer durations (8-h) were used to estimate AEGL values that are protective of human health (NRC 2001). The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with time scaling a 6-h exposure to a 10-min value. The AEGL values for isobutyronitrile are presented in Table 1-12. 

Aliphatic Nitriles 47 TABLE 1-12 AEGL Values for Isobutyronitrile End Point Classification 10 min 30 min 1h 4h 8h (Reference) AEGL-1 NRa NRa NRa NRa NRa Insufficient data (nondisabling) AEGL-2 2.5 ppm 2.5 ppm 2.0 ppm 1.3 ppm 0.83 ppm One-third of (disabling) (7.1 (7.1 (5.7 (3.7 (2.3 AEGL-3 values mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) AEGL-3 7.6 ppm 7.6 ppm 6.1 ppm 3.8 ppm 2.5 ppm No-effect level for (lethal) (22 (22 (17 (11 (7.1 maternal lethality mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) (Saillenfait et al. 1993) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 3.2. Introduction Isobutyronitrile is a colorless liquid at ambient temperature and pressure. It has an almond-like odor and may cause irritation or burning of the eyes and skin. Isobutyronitrile is produced from isobutyraldehyde by cyanation with ammonia. It is used in organic synthesis, as a catalyst in the polymerization of ethylene, as an intermediate for insecticides, and as a gasoline additive (HSDB 2003a). The chemical and physical properties of isobutyronitrile are presented in Table 1-13. 3.3. Human Toxicity Data 3.3.1. Acute Lethality Information concerning death in humans following inhalation exposure to isobutyronitrile is not available. 3.3.2. Nonlethal Toxicity 3.3.2.1. Case Report A 44-year-old man was occupationally exposed to isobutyronitrile while filling a tank (Thiess and Hey 1969). He became unconscious, exhibited tonic and clonic movements of the arms, had a soft thready pulse, exhibited dilated pupils, had shallow and gasping breathing, and secreted viscous, glossy mucous from glands of the oropharyngeal area. He was admitted to the hospital, and his 

48 Acute Exposure Guideline Levels TABLE 1-13 Chemical and Physical Data for Isobutyronitrile Parameter Data Reference Common name Isobutyronitrile HSDB 2003a Synonyms 2-Methylpropanenitrile; 1-cyano-1-methylethane; HSDB 2003a 2-cyanopropane; 2-methylpropionitrile; dimethylacetonitrile; isopropyl cyanide; propanoic acid, 2-methyl-, nitrile CAS registry no. 78-82-0 HSDB 2003a Chemical formula C4H7N HSDB 2003a Molecular weight 69.1 HSDB 2003a Physical state Colorless liquid HSDB 2003a Melting point -71.5°C HSDB 2003a Boiling point 103.9°C HSDB 2003a Density/Specific gravity 0.7704 at 20°C HSDB 2003a Solubility Slightly soluble in water; soluble in alcohol HSDB 2003a and ether Vapor density 2.38 (air = 1) HSDB 2003a Vapor pressure 32.7 mm Hg at 25°C HSDB 2003a 3 Conversion factors in air 1 ppm = 2.83 mg/m NIOSH 2011b 1 mg/m3 = 0.35 ppm condition worsened; tonic and clonic movements continued and were accompa- nied by clenched teeth, a cold sweat on the forehead, and cyanosis. He was treated with norepinephrine, amyl nitrite, sodium nitrite, and sodium thiosulfate, followed by lobeline and phenobarbital. He improved within 5-10 min of treat- ment, and regained consciousness 4 h after the exposure. He complained of a headache for a few days. He was discharged from the hospital 14 days after the accident. The report did not provide estimates of the exposure concentration or duration. Zeller et al. (1969) reported that two workers exposed to isobutyronitrile experienced headache, dizziness, and vomiting 10-60 min after exposure. The severity of symptoms reportedly varied with concentration and exposure dura- tion; however, no concentration or duration information was reported. An exposure of “a few minutes” to isobutyronitrile at estimated concentra- tions of 20-25 ppm during a spill did not produce symptoms of cyanide poison- ing (AIHA 1992). 3.3.3. Developmental and Reproductive Toxicity Developmental and reproductive studies regarding acute human exposure to isobutyronitrile were not available. 

Aliphatic Nitriles 49 3.3.4. Genotoxicity Genotoxicity studies regarding acute human exposure to isobutyronitrile were not available. 3.3.5. Carcinogenicity Carcinogenicity studies regarding human exposure to isobutyronitrile were not available. 3.3.6. Summary Data concerning human exposure to isobutyronitrile are limited to occupa- tional case reports lacking exposure concentration and duration information. The reports indicate that clinical signs are consistent with those of cyanide poison- ing. No human studies of the developmental or reproductive toxicity, genotoxi- city, or carcinogenicity of isobutryonitrile were available. 3.4. Animal Toxicity Data 3.4.1. Acute Lethality 3.4.1.1. Rats Groups of five male and five female CRL:CD(SD)BR rats were exposed to isobutyronitrile at target vapor concentrations of 1,200, 1,800, or 2,700 ppm for 1 h, followed by a 14-day observation period (Katz 1986). Exposures were conducted in 420-L stainless steel and glass inhalation chambers maintained under negative pressure and at 13 air changes per hour. Vapors were generated by metering the test material dropwise into a heated glass bead-packed column supplied with metered dried, oil-free compressed air. Chamber concentrations were determined four times per hour by an infrared analyzer equipped for auto- mated sampling and analysis. Temperature and humidity were determined twice per hour and test material distribution was determined initially by measurement from numerous chamber positions and then from a fixed reference position. Ac- tual mean exposure concentrations were 1,248 ± 62 ppm, 1,778 ± 16 ppm, and 2,709 ± 34 ppm for the 1,200-, 1,800-, and 2,700-ppm groups, respectively. All animals exposed at 1,800 and 2,700 ppm exhibited lethargy during exposure; the effect was minor at 1,800 ppm, whereas rats in the 2,700-ppm group developed gait disturbances followed by narcosis. Lethargy was observed in 1,800- and 2,700-ppm animals for up to 24 h after exposure. No clinical signs were noted at 1,200 ppm. Mortality was 1/5 (males) and 0/5 (females) at 1,200 ppm; 4/5 (males) and 1/5 (females) at 1,800 ppm; and 5/5 (males) and 3/5 (females) at 2,700 ppm. All deaths occurred within 48-h post-exposure. One-hour LC10 val- 

50 Acute Exposure Guideline Levels ues of 1,143 ppm and 1,630 ppm were calculated for males and females, respec- tively; the combined LC10 was 1,173 ppm. A combined LC01 of 677 ppm was also calculated. No treatment-related histopathologic effects were reported. As an adjunct to the above study, groups of four male CRL:CD(SD)BR rats were exposed to isobutyronitrile at target vapor concentrations of 0, 1,200, 1,800, or 2,700 ppm for 1 h (Eastman Kodak 1986a). The exposures were con- ducted using the same method as the study by Katz (1986). Pulmonary function tests (lung volume and capacity, ventilation, dynamic compliance, and airway resistance) were performed on the day before and the day after exposure. Ani- mals were killed on day 7, and no necropsies were performed. All four animals from the 2,700-ppm group and two of four animals from the 1,800-ppm group died before pulmonary function tests could be performed. The small sample size and high mortality prevented statistical analysis of the pulmonary function data. However, “appreciable” differences were noted between pre- and post-exposure values for the four 1,200-ppm and two surviving 1,800-ppm rats. Differences were noted in expiratory reserve volume, residual volume, dynamic compliance (up to 76% decrease), and forced expiratory volume (FEV) 10%. In another study, five male and five female CRL:CD(SD)BR rats were similarly exposed to a isobutyronitrile at a target vapor concentration of 1,200 ppm for 1 h (Eastman Kodak 1986b). Actual mean vapor concentrations were 1,233 ± 15 ppm for males and 1,177 ± 53 ppm for females. One male died with- in 1 day following exposure. No other effects were reported. Tsurumi and Kawada (1971) exposed groups of 10 rats (sex and strain not specified) to a nominally saturated atmosphere (approximately 37,000 ppm at 20°C) of isobutyronitrile for up to 10 min. Surviving animals were observed for 24 h, and the fraction of deaths occurring as a function of exposure duration was recorded (see Table 1-14). Tsurumi and Kawada (1971) administered single intraperitoneal or oral doses of isobutyronitrile to groups of six female Wistar rats, and the animals were observed for 72 h. Clinical signs included clonic movements and decreased respiratory frequency and depth, followed by complete respiratory failure and death. An intraperitoneal LD50 of 190 mg/kg and oral LD50 of 100 mg/kg were calculated. 3.4.1.2. Mice Tsurumi and Kawada (1971) exposed groups of 10 mice (sex and strain not specified) to a nominally saturated atmosphere (approximately 37,000 ppm at 20°C) of isobutyronitrile for up to 10 min. Surviving animals were observed for 24 h, and the fraction of deaths occurring as a function of exposure duration was recorded (see Table 1-14). 

Aliphatic Nitriles 51 TABLE 1-14 Deaths within 24 Hours of Exposure to Isobutyronitrile at Nominal Saturation of 37,000 ppm Species Exposure Duration (min) Mortality Rats 4.0 0/10 5.0 1/10 6.0 4/10 8.0 6/10 10.0 10/10 Mice 0.25 0/10 0.5 3/10 1.0 5/10 1.5 7/10 2.0 10/10 Source: Data from Tsurumi and Kawada 1971. Tsurumi and Kawada (1971) administered single intraperitoneal doses of isobutyronitrile ranging from 0.4 to 0.8 mg/kg to groups of male mice, and the animals were observed for 72 h. Clinical signs included clonic movements and decreased respiratory frequency and depth, followed by complete respiratory failure 20-30 min after injection and death. The lethal dose could not be deter- mined due to the potency of the compound and the difficulty of administering smaller doses. The oral LD50 for isobutyronitrile was estimated to be 25 mg/kg in male ddY mice (Tanii and Hashimoto 1986). 3.4.1.3. Rabbits Rabbits (sex, strain, age, and number not reported) were administered iso- butyronitrile intravenously to assess effects on cardiac function (Tsurumi and Kawada 1971). At doses below 0.01 mg/kg, no effects were noted. At doses above 0.01 mg/kg, decreased blood pressure, blood flow, and respiration were noted. A dose of 0.1 mg/kg resulted in death within 30-40 min after exposure. 3.4.2. Nonlethal Toxicity Smyth et al. (1962) reported that exposure of six rats to isobutyronitrile at a nominal concentration of 500 ppm for 4 h resulted in no mortality. No other details were available. In a repeated-exposure study, groups of 10 male and 10 female Wistar rats were administered isobutyronitrile once a day for 14 days either by intraperitoneal injection (23.2 or 38.6 mg/kg) or orally (0.2 g/kg). No clinical signs or death were 

52 Acute Exposure Guideline Levels reported. Males in the 0.2 g/kg-group had decreased mean body weights, and males and females exposed at 0.2 g/kg had slightly increased stomach, liver, and adrenal weights compared with controls. Rats in the 38.6 mg/kg-group had paren- chymous liver degeneration (Tsurumi and Kawada 1971). 3.4.3. Developmental and Reproductive Toxicity Saillenfait et al. (1993) exposed groups of 21 pregnant Sprague-Dawley rats to isobutyronitrile at nominal concentrations of 0, 50, 100, 200, or 300 ppm (analytic concentrations were 54 ± 2.3, 98 ± 10, 208 ± 12.4, or 308 ± 18.6 ppm, respectively) for 6 h/day on days 6-20 of gestation. Exposures were conducted in a 200-L stainless steel dynamic flow inhalation chamber. The chamber tem- perature was set at 23 ± 2°C and the relative humidity at 50 ± 5%. Vapors were generated by bubbling air through a flask containing the test compound and were mixed with filtered room air to achieve the desired concentration. The nominal concentrations were calculated from the ratio of the amount of test compound vaporized to the total chamber air flow during the exposure period. Analytic concentrations were determined once every hour during each 6-h expo- sure period using gas-liquid chromatography. One of 21 exposed females died in the 200-ppm group, and 3 of 21 females died in the 300-ppm group. The day on which the animals died and number of exposures that occurred prior to death were not reported. No treatment-related effects on maternal absolute body weights or body weight gain on gestation days 6-20 were found. There were also no treatment-related effects on pregnancy rate, number of implantations or live fetuses, or sex ratio across groups. A significant (p < 0.01) increase in the inci- dence of embryonic resorptions was observed at 300 ppm compared with the concurrent controls. A concentration-related decrease in fetal weight was ob- served in females in the 200-ppm group (8% lower than control, p < 0.05) and males and females in the 300-ppm group (14-16% lower than controls, p < 0.05). The only major malformation observed was a unilateral hydronephrosis at 300 ppm. There was no evidence of reproductive or developmental toxicity in the absence of maternal toxicity. 3.4.4. Genotoxicity Studies of the genotoxic potential of isobutyronitrile were not available. 3.4.5. Carcinogenicity No information concerning the carcinogenicity of isobutyronitrile in ani- mals was available. 

Aliphatic Nitriles 53 3.4.6. Summary One-hour LC10 values for isobutyronitrile of 1,143 and 1,630 ppm for male and female rats, respectively, have been reported (Katz 1986). On the basis of this data, the combined LC10 for rats is 1,173 ppm, and the combined LC01 is 677 ppm. Clinical signs in rats included lethargy, gait disturbances, and narco- sis. Pulmonary function effects were evidenced by changes in expiratory reserve volume, residual volume, dynamic compliance (up to 76% decrease), and FEV10% (Eastman Kodak, 1986a). Acute inhalation of saturated atmospheres of isobutyronitrile suggest that mice are more sensitive than rats (Tsurumi and Ka- wada 1971). Clinical signs from oral, intraperitoneal, and inhalation exposure to isobutyronitrile are consistent with those seen in cyanide poisoning. In a devel- opmental toxicity study, Saillenfait et al. (1993) observed an increase in the in- cidences of nonsurviving implants and embryonic resorptions at 300 ppm com- pared with controls, concentration-related decreases in fetal weight at 200 and 300 ppm, and unilateral hydronephrosis at 300 ppm. Maternal deaths were ob- served at 200 and 300 ppm; no maternal or fetal effects were found at 50 or 100 ppm. No genotoxicity or carcinogenicity data on isobutyronitrile were available. 3.5. Data Analysis for AEGL-1 3.5.1. Human Data Relevant to AEGL-1 No human data on isobutyronitrile consistent with the definition of AEGL-1 were available. 3.5.2. Animal Data Relevant to AEGL-1 No animal data on isobutyronitrile consistent with the definition of AEGL-1 were available. 3.5.3 Derivation of AEGL-1 Values Data were insufficient to derive AEGL-1 values for isobutyronitrile. Be- cause the available data do not suggests a particularly steep concentration- response curve for this chemical, it was considered inappropriate to estimate AEGL-1 values by dividing the AEGL-2 values by 3. Therefore, AEGL-1 val- ues are not recommended for isobutyronitrile. 3.6. Data Analysis for AEGL-2 3.6.1. Human Data Relevant to AEGL-2 No human data on isobutyronitrile consistent with the definition of AEGL- 2 were available. 

54 Acute Exposure Guideline Levels 3.6.2. Animal Data Relevant to AEGL-2 No maternal or fetal effects were observed in pregnant rats exposed to iso- butyronitrile at 50 or 100 ppm for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993); however, maternal lethality was observed in dams exposed at 200 ppm. 3.6.3. Derivation of AEGL-2 Values The no-effect level of 100 ppm for maternal or fetal effects in pregnant rats exposed to isobutyronitrile for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993) was not considered an appropriate basis for deriving AEGL-2 values because lethality was observed in the dams exposed at the next highest concen- tration (200 ppm). Furthermore, although the Saillenfait et al. (1993) study in- volved repeated exposures and identified no-effect levels for mortality that were below those observed in studies of single exposures of non-pregnant animals, it is possible that sensitivity to isobutyronitrile could increase during pregnancy. Therefore, the no-effect level of 100 ppm for maternal and fetal toxicity (mortal- ity) is not an appropriate end point for AEGL-2 values. No other data identifying a point of departure for derivation of AEGL-2 values were identified. Therefore, AEGL-2 values were derived by dividing AEGL-3 values by 3. AEGL-2 values for isobutyronitrile are presented in Table 1-15. 3.7. Data Analysis for AEGL-3 3.7.1. Human Data Relevant to AEGL-3 No human data on isobutyronitrile consistent with the definition of AEGL- 3 were available. 3.7.2. Animal Data Relevant to AEGL-3 One-hour LC10 values for isobutyronitrile of 1,143 and 1,630 ppm for male and female rats, respectively, have been reported (Katz 1986). On the basis of this data, the combined LC10 for rats is 1,173 ppm, and the combined LC01 is 677 ppm. In a study of repeated exposure to iosbutyronitrile, the no-effect level for lethality in pregnant rats exposed for 6 h/day on gestational days 6-20 was 100 ppm (Saillenfait et al. 1993); maternal lethality was observed in dams ex- posed at 200 ppm. TABLE 1-15 AEGL-2 Values for Isobutyronitrile 10 min 30 min 1h 4h 8h 2.5 ppm 2.5 ppm 2.0 ppm 1.3 ppm 0.83 ppm (7.1 mg/m3) (7.1 mg/m3) (5.7 mg/m3) (3.7 mg/m3) (2.3 mg/m3) 

Aliphatic Nitriles 55 3.7.3. Derivation of AEGL-3 Values The no-effect level of 100 ppm for maternal mortality in pregnant rats ex- posed to isobutyronitrile for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993) was selected as the point of departure for deriving AEGL-3 values. Alt- hough the study involved repeated exposures, the day on which the dams died and the number of exposures at the next higher dose (200 ppm) that occurred prior to death were not reported. Therefore, it is possible that the deaths could have resulted from a single exposure. The Saillenfait et al. (1993) study identi- fied no-effect levels for mortality that were below those observed in studies with single exposures of nonpregnant animals; this may reflect a higher sensitivity of pregnant animals to lethal effects of isobutyronitrile. Therefore, the no-effect level of 100 ppm for maternal toxicity (mortality) was considered an appropriate end point for AEGL-3 values. An intraspecies uncertainty factor of 3 was applied because studies of ac- cidental and occupational exposures to hydrogen cyanide (the metabolically- liberated toxicant) indicate that there are individual differences in sensitivity to this chemical but that the differences are not expected to exceed 3-fold (NRC 2002). An interspecies uncertainty factor of 10 was also applied because no comparable studies of similar exposures (repeated inhalation exposure during gestation) in other species were available. Thus, the total uncertainty factor is 30. Time scaling was performed using the equation Cn × t = k, where the expo- nent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). This equation has been shown to describe the concentration-exposure duration relationship for many irritant and systemically acting vapors and gases. Data on iosbutyronitrile were insufficient for deriving an empirical value for n. Therefore, default values of n = 3 to extrapolate to shorter durations (30 min, 1h, and 4 h) and n = 1 to extrapo- late longer durations (8-h) were used to estimate AEGL values that are protec- tive of human health (NRC 2001). The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with time scal- ing a 6-h exposure to a 10-min value. AEGL-3 values for isobutyronitrile are presented in Table 1-16, and the calculations are presented in Appendix B. 3.8. Summary of AEGLs 3.8.1. AEGL Values and Toxicity End Points The AEGL values for isobutyronitrile are presented in Table 1-17. Data were insufficient to derive AEGL-1 values. Data were also inadequate for deriv- ing AEGL-2 values, so they were estimated by dividing the AEGL-3 values by 3. A no-effect level for maternal mortality and increased fetal resorptions in pregnant rats exposed to isobutyronitrile on gestational days 6-20 was used as the basis of AEGL-3 values. 

56 Acute Exposure Guideline Levels TABLE 1-16 AEGL-3 Values for Isobutyronitrile 10 min 30 min 1h 4h 8h 7.6 ppm 7.6 ppm 6.1 ppm 3.8 ppm 2.5 ppm (22 mg/m3) (22 mg/m3) (17 mg/m3) (11 mg/m3) (7.1 mg/m3) TABLE 1-17 AEGL-3 Values for Isobutyronitrile Classification 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa (nondisabling) AEGL-2 2.5 ppm 2.5 ppm 2.0 ppm 1.3 ppm 0.83 ppm (disabling) (7.1 mg/m3) (7.1 mg/m3) (5.7 mg/m3) (3.7 mg/m3) (2.3 mg/m3) AEGL-3 7.6 ppm 7.6 ppm 6.1 ppm 3.8 ppm 2.5 ppm (lethal) (22 mg/m3) (22 mg/m3) (17 mg/m3) (11 mg/m3) (7.1 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 3.8.2. Other Standards and Guidelines Standards and guidelines for short-term exposures to isobutyronitrile are presented in Table 1-18. The emergency response planning guideline 1 (ERPG- 1) of 10 ppm is based on the lowest odor threshold reported for methacryloni- trile (no odor threshold reported for isobutyronitrile). The ERPG-2 of 50 ppm is based on a weight-of-evidence approach that considered data from acute and subchronic studies in rats and symptoms reported in workers. The ERPG-3 of 200 ppm is based on an LC10 value from an acute exposure study in rats (Katz 1986). The National Institute for Occupational Safety and Health’s recommend- ed exposure limit of 8 ppm is based on evidence that selected nitrile compounds are metabolized to cyanide ion which causes numerous systemic effects. 3.8.3. Data Adequacy and Research Needs Data were insufficient to derive AEGL-1 values for isobutyronitrile. Only one set of well-conducted animal studies and one developmental toxicity study were available as a basis for deriving AEGL-2 and AEGL-3 values. 4. PROPIONITRILE 4.1. Summary Propionitrile is a selective solvent used commercially in hydrocarbon separation and in petroleum refining. It has served as a raw material in manufac- turing pharmaceuticals and as a setting agent for resins (NIOSH 1978). Propi- onitrile is a colorless liquid at ambient temperature and pressure. It has a pleasant 

Aliphatic Nitriles 57 TABLE 1-18 Standards and Guidelines for Isobutyronitrile Exposure Duration Guideline 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa AEGL-2 2.5 ppm 2.5 ppm 2.0 ppm 1.3 ppm 0.83 ppm (7.1 mg/m3) (7.1 mg/m3) (5.7 mg/m3) (3.7 mg/m3) (2.3 mg/m3) AEGL-3 7.6 ppm 7.6 ppm 6.1 ppm 3.8 ppm 2.5 ppm (22 mg/m3) (22 mg/m3) (17 mg/m3) (11 mg/m3) (7.1 mg/m3) ERPG-1 (AIHA)b – – 10 ppm – – (28 mg/m3) ERPG-2 (AIHA)b – – 50 ppm – – (140 mg/m3) ERPG-3 (AIHA)b – – 200 ppm – – (570 mg/m3) REL-TWA (NIOSH)c – – – – 8 ppm (22 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. b ERPG (emergency response planning guidelines, American Industrial Hygiene Associa- tions) (AIHA 1992, 2013). ERPG-1 is the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 h without experiencing other than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor. The ERPG-1 for isobutyronitrile is based on odor data on methacrylonitrile. ERPG-2 is the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 h without experiencing or developing irreversi- ble or other serious health effects or symptoms that could impair an individual’s ability to take protective action. The ERPG-2 for isobutyronitrile is based on rat LC10 and pulmo- nary function data. ERPG-3 is the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 h without experiencing or developing life- threatening health effects. The ERPG-3 for isobutyronitrile is based on rat LC10 data. c REL-TWA (recommended exposure limit—time-weighted average, National Institute for Occupational Safety and Health) (NIOSH 2011b) is defined as a time-weighted aver- age concentrations for up to a 10-h workday during a 40-h workweek. pleasant, ethereal, sweetish odor and may cause irritation or burning of the eyes and skin. It is metabolized to cyanide in the body. Depending on the level of exposure, signs of intoxication may include weakness, headache, confusion, nausea, vomiting, convulsion, dilated pupils, weak pulse, dyspnea, and cyanosis (HSDB 2002). These clinical signs are similar to those that have been reported in people exposed to hydrogen cyanide (Blanc et al. 1985), although the time course for propionitrile intoxication is more protracted. Chemical-specific data were insufficient to derive AEGL-1 values for propionitrile, so no values are recommended. Data on propionitrile were also 

58 Acute Exposure Guideline Levels insufficient to derive AEGL-2 values, so AEGL-2 values were derived by divid- ing AEGL-3 values by 3. The threshold level for maternal mortality and increased fetal resorptions in pregnant rats exposed to propionitrile at 150 ppm for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993) was used as the point of departure for deriving AEGL-3 values for propionitrile. Although the study involved repeated expo- sures, fetal death can occur during a narrow developmental window and does not necessarily require repeated exposures (Van Raaij et al. 2003). Therefore, the observation of increased fetal resorptions following repeated gestational ex- posure is considered a relevant end point for deriving AEGL-3 values. An intra- species uncertainty factor of 3 was applied because studies of accidental and occupational exposures to hydrogen cyanide (the metabolically-liberated toxi- cant) indicate that there are individual differences in sensitivity to this chemical but that the differences are not expected to exceed 3-fold (NRC 2002). An inter- species uncertainty factor of 10 was also applied because no comparable studies of similar exposures (repeated inhalation exposure during gestation) in other species were available. Thus, the total uncertainty factor is 30. Time scaling was performed using the equation Cn × t = k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). Data on propionitrile were insufficient for deriving an empirical value for n. Therefore, default values of n = 3 to extrapolate to shorter durations (30 min, 1h, and 4 h) and n = 1 to extrapolate longer durations (8-h) were used to estimate AEGL values that are protective of human health (NRC 2001). The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with time scaling a 6-h exposure to a 10-min value. AEGL values for propionitrile are presented in Table 1-19. TABLE 1-19 AEGL Values for Propionitrile End Point Classification 10 min 30 min 1h 4h 8h (Reference) AEGL-1 NRa NRa NRa NRa NRa Insufficient data (nondisabling) AEGL-2 3.7 ppm 3.7 ppm 3.0 ppm 1.9 ppm 1.3 ppm One-third of (disabling) (8.3 (8.3 (6.8 (4.3 (2.9 AEGL-3 values mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) AEGL-3 11 ppm 11 ppm 9.1 ppm 5.7 ppm 3.8 ppm No-effect (lethal) (25 (25 (20 (13 (8.6 level for mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) maternal and fetal mortality (Saillenfait et al. 1993) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 

Aliphatic Nitriles 59 4.2. Introduction Propionitrile is a colorless liquid at ambient temperature and pressure. It has a pleasant, ethereal, sweetish odor and may cause irritation or burning of the eyes and skin. Propionitrile is produced using a copper or nickel catalyst in selective hy- drogenation of acrylonitrile, as a by-product during the electroreduction of acrylo- nitrile to form adiponitrile, or may be prepared by dehydration of propionamide or by distillation of ethyl sulfate and concentrated aqueous potassium cyanide (Thompson 1972; ITTI 1977; NIOSH 1978). It is used as a solvent in petroleum refining, as a raw material in drug manufacturing, and in manufacturing cyanoace- tates (HSDB 2002). The chemical and physical properties of propionitrile are presented in Ta- ble 1-20. 4.3. Human Toxicity Data 4.3.1. Acute Lethality Information concerning death in humans following inhalation exposure to propionitrile was not available. TABLE 1-20 Chemical and Physical Data for Propionitrile Parameter Data Reference Common name Propionitrile HSDB 2002 Synonyms Cyanoethane, ether cyanatus; ethyl cyanide; HSDB 2002 hydrocyanic ether; propanenitrile; propionic nitrile; propiononitrile; propylnitrile CAS regsitry no. 107-12-0 HSDB 2002 Chemical formula C3H5N HSDB 2002 Molecular weight 55.08 HSDB 2002 Physical state Colorless liquid HSDB 2002 Melting point -91.8°C HSDB 2002 Boiling point 97.2°C HSDB 2002 Density/Specific gravity 0.7818 at 20°C/4°C HSDB 2002 5 Solubility In water, 1.03 × 10 mg/L at 25°C; miscible HSDB 2002 with alcohol, ether Vapor density 1.9 (air = 1) HSDB 2002 Vapor pressure 47.4 mm Hg at 25°C HSDB 2002 3 Conversion factors in air 1 ppm = 2.25 mg/m NIOSH 2011c 1 mg/m3 = 0.437 ppm 

60 Acute Exposure Guideline Levels 4.3.2. Nonlethal Toxicity 4.3.2.1. Case Reports A healthy 55-year-old man noticed that a pump in the chemical plant where he worked had a leaking pipe fitting (Bismuth et al. 1987). He entered the area to repair the leak wearing protective gloves but no respirator or other pro- tective clothing. The pump was connected to a liquid propionitrile source and the worker inhaled propionitrile vapors and was exposed dermally to the liquid. He rapidly lost consciousness and developed metabolic acidosis consistent with cyanide poisoning. He was treated with intravenous hydroxycobalamin and so- dium thiosulfate, and his symptoms resolved within 1 h. No exposure concentra- tion or duration was reported. Scolnick et al. (1993) describe cases of two male workers (ages 28 and 34 years) exposed to propionitrile at an organic chemical plant. Their assignment was to treat waste discharge containing ammonia and water by stirring it to make a slurry suitable for disposal. They wore protective clothing, boots, and gloves but did not respirators. The 28-year-old occasionally had to bend within 2-3 inches of the slurry, and was found collapsed after approximately 7 h of ex- posure. Upon arrival at the hospital, he was deeply comatose, and within 10 min he experienced tonic/clonic, generalized seizures. Since cyanide poisoning was suspected, he was treated with sodium nitrite followed by sodium thiosulfate approximately 90 min after he arrived at the hospital. He regained consciousness shortly thereafter and no further seizures occurred. He was ventilated when a chest X-ray indicated bilateral interstitial infiltrates. (By this time, chemical plant officials had notified the hospital that a contaminant of unreacted propi- onitrile overlaying the waste slurry had been detected). Because of continuing complaints of lethargy and headache, the patient was treated with hyperbaric oxygen. He was released from the hospital 48 h later with resolving pneumonia. He continued to complain of severe headaches and dizziness for the next 30 days. No remarkable symptoms reported at the 6-month follow-up exam. The 34-year-old worker complained of headache, nausea, and dizziness after 2 h of working in the same area. He left the work area, vomited, and went to the cafete- ria to lay down. He was found confused and disoriented 5 h later, and was taken to the same emergency room as the 28-year-old worker. He had a bad headache and nausea and vomited once. His chest X-ray was normal; however, his blood cyanide level was elevated 6 h after admission. He received the cyanide antidote and was discharged 24 h later and had an uneventful recovery. Ambient air sam- pling of the work area performed shortly after the men were discovered meas- ured propionitrile at 33.8 ppm. Analysis of the slurry indicated 80% propi- onitrile. 

Aliphatic Nitriles 61 4.3.3. Developmental and Reproductive Toxicity Developmental and reproductive studies of acute human exposure to pro- pionitrile were not available. 4.3.4. Genotoxicity Genotoxic studies of acute human exposure to propionitrile were not available. 4.3.5. Carcinogenicity Carcinogenicity studies of human exposure to propionitrile were not avail- able. 4.3.6. Summary Only case reports of human exposure to propionitrile are available. A total of three men were occupationally exposed to propionitrile, and developed signs consistent with cyanide poisoning. They all recovered after treatment for cya- nide poisoning. No human studies of the developmental or reproductive toxicity, genotoxicity, or carcinogenicity of propionitrile were available. 4.4 Animal Toxicity Data 4.4.1. Acute Lethality 4.4.1.1. Rats Groups of five male and five female Sprague-Dawley rats were exposed to propionitrile at 690, 1,100, 1,700, 2,800, 4,400, or 6,900 ppm for 4 h (Younger Labs 1978). Animals were placed in a cage (9” × 16” × 7”) suspend- ed in the middle of a 210-L drum-like chamber. The chamber was equipped with a circulating fan (6” blade) and a glass window at one end for viewing. The sample was introduced into the chamber through a special port with a No. 27 needle. As the sample was introduced into the chamber it was spread to- ward the surface areas to facilitate evaporation. The fan was operated at max- imum speed during introduction of the sample and for an additional 2 min, and then turned off. The rats were observed for signs of toxicity during exposure and surviving animals were observed for 14 days. The average chamber tem- perature was 24-25°C and average humidity was 70%. Salivation, lethargy, weakness, tremors, convulsions, collapse, and death were observed during exposure. Macroscopic examination of decedents found hemorrhagic lungs, 

62 Acute Exposure Guideline Levels liver discoloration, and acute gastrointestinal inflammation. The viscera of animals surviving the 14-day follow-up period appeared normal. An LC50 of 1,441 ppm was calculated. Mortality data from this study are summarized in Table 1-21. In another study, lethargy, labored breathing, tremors, convulsions, col- lapse, and death were observed in a group of six male Sprague-Dawley rats ex- posed to propionitrile at 39,432 ppm for 1.25 h (Younger Labs 1979). Chamber temperature was 26°C and humidity was 80%. Hemorrhagic lungs and gastroin- testinal inflammation were observed at necropsy. No other experimental details were available. Smyth et al. (1962) reported that two of six rats died after being exposed to a nominal concentration of propionitrile at 500 ppm for 4 h. 4.4.1.2. Mice Groups of 10 male CD-1 mice were exposed to five or six concentrations of propionitrile ranging from 70-400 ppm for 60 min (Willhite and Smith 1981). Actual individual group exposure concentrations were not reported. Propionitrile (99%) was mixed with a stream of dehumidified air (10 L/min) and delivered to a single pass 45-L glass inhalation chamber. Samples were collected every 5 min using a gas-tight syringe and concentrations were analyzed by gas chroma- tography. The mice exhibited dyspnea, tachypnea, gasping, tremors, convul- sions, and corneal opacity 30-300 min after initial contact with propionitrile. All mice in the 400-ppm group died within 180 min of initial contact, and delayed deaths were observed up to 3 days after exposure to lower (unspecified) concen- trations. The livers of exposed mice were bright red compared with controls. Gross and histopathologic examination of pulmonary tissues from mice exposed to lethal concentrations of propionitrile showed no marked difference compared with air-exposed controls. An LC50 of 163 ppm (95% confidence limit = 116- 211 ppm) was calculated. TABLE 1-21 Mortality in Sprague-Dawley Rats Exposed to Propionitrile for 4 Hours Males Females Concentration (ppm) Mortality Time to death Mortality Time to death 690 0/5 – 0/5 – 1,100 5/5 <4 h (n =1); 1 d (n = 4) 0/5 – 1,700 5/5 <4 h (n = 2); 1 d (n = 1); 0/5 – 2 d (n = 1); 13 d (n = 1) 2,800 5/5 <4 h 3/5 <4 h (n = 1); 1 d (n = 2) 4,400 5/5 <4 h 5/5 1d 6,900 5/5 <4 h 5/5 <4 h Source: Adapted from Younger Labs 1978. 

Aliphatic Nitriles 63 An oral LD50 for propionitrile was estimated to be 36 mg/kg in male ddY mice (Tanii and Hashimoto 1984). An intraperitoneal LD50 of 34 mg/kg for mice was reported (Lewis 1996). No further information was available. 4.4.2. Nonlethal Toxicity No information concerning nonlethal toxicity from inhalation exposure to propionitrile was available. However, several single- or repeated-exposure sub- cutaneous studies at 2-5 mg/kg document the production of duodenal ulcers in rats (Szabo and Selye 1972; Dzau et al. 1975; Giampaolo et al. 1975; Haith et al. 1975). Male rats were more resistant than female rats to these ulcerogenic ef- fects (Robert et al. 1975). The development of the propionitrile-induced ulcers is associated with enhanced gastric acid output, delayed gastric emptying (Szabo et al. 1976), and the accumulation of highly acidic gastric juice (Szabo et al. 1977). Vagotomy eliminated the occurrence of propionitrile-induced ulcers, and hy- pophysectomy decreased the incidence of the lesions (Haith et al. 1975). No clinical reports of duodenal ulcer associated with occupational exposure to pro- pionitrile were found. 4.4.3. Developmental and Reproductive Toxicity Saillenfait et al. (1993) exposed groups of 22-23 pregnant Sprague- Dawley rats to propionitrile at nominal concentrations of 0, 50, 100, 150, or 200 ppm (analytic concentrations were 0, 52 ± 4.9, 97 ± 7.7, 151 ± 13.9, or 200 ± 15.4 ppm, respectively) for 6 h/day on days 6-20 of gestation. Exposures were conducted in a 200-L stainless steel dynamic flow inhalation chamber. The chamber temperature was set at 23 ± 2°C and the relative humidity at 50 ± 5%. Vapors were generated by bubbling additional air through a flask containing the test compound and were mixed with filtered room air to achieve the desired concentration. The nominal concentrations were calculated from the ratio of the amount of test compound vaporized to the total chamber air flow during the ex- posure period. Analytic concentrations were determined once every hour during each 6-h exposure period using gas-liquid chromatography. Two of 22 females died in the 200-ppm group, and no other maternal deaths were observed; the day on which the animals died or the number of exposures that occurred prior to death were not reported. There were no treatment-related effects on maternal absolute body weight or body weight gain on gestation days 6-20. No treatment- related effects on pregnancy rate, number of implantations or live fetuses, or sex ratio across groups were found. A significant (p < 0.01) increase in the incidenc- es of nonsurviving implants and embryonic resorptions was observed at 200 ppm compared with controls. One litter was completely resorbed at 200 ppm. A concentration-related decrease in fetal weight was observed and was statistically significant in 200-ppm males (p < 0.01) and females (p < 0.05). These decreases 

64 Acute Exposure Guideline Levels amounted to 11-13% of the control values. No treatment-related fetal malfor- mations were observed. Although this study involved repeated exposures, fetal death is a relevant end point for deriving AEGL values because fetal toxicity could result from a single exposure. In addition, although the study identified no-effect levels for mortality that were below those observed in studies of single exposures of nonpregnant animals, it is possible that sensitivity to propionitrile could increase during pregnancy. Results of an oral exposure study in pregnant rats show that propionitrile can induce fetal toxicity after a single exposure (Saillenfait and Sabaté 2000). Pregnant Sprague-Dawley rats were administered a single oral dose of propi- onitrile (180 mg/kg) on gestational day 10, and fetuses were examined for mal- formations on gestational day 12. Embryo viability was not affected, but abnor- mal development, including “overall poor and abnormal development” and misdirected allantois, trunk, and caudal extremities, was observed. A single parenteral administration of propionitrile at 0.54-1.51 mmol/kg during the early primitive streak stage of pregnancy in Syrian Golden hamsters induced dose-dependent signs of intoxication (intense dyspnea, incoordination, hypothermia, salivation, and convulsions with opisthotonis) (Willhite et al. 1981a). Frank malformations (encephalocele, bifurcated ribs, and fused ribs) were observed at doses which also caused clear signs of maternal intoxication and increased mortality. Propionitrile induced mesodermal shrinkage, collapse, decreased mitotic figures, and necrobiosis. Malformations of the central nervous system were accompanied by congenital defects of the basisphenoid and basioc- cipital (Willhite et al. 1981b). Propionitrile-induced maternal and developmental toxicity was prevented by prophylactic and repeated thiosulfate injections. De- creases in circulating and brain cyanide concentrations after thiosulfate admin- istration and the fact that thiosulfate prevented maternal and developmental tox- icity, suggest that metabolically liberated cyanide was responsible for the observed effects (Willhite and Smith 1981). Johannsen et al. (1986) administered aqueous solutions of propionitrile at concentrations of 0, 20, 40, or 80 mg/kg by gavage to pregnant rats on days 6-19 of gestation. Maternal body weights were decreased and one death occurred in high-dose dams; no maternal effects were noted at lower concentrations. In- creases in early resorptions and post-implantation losses and decreases in fetal body weight were noted only in the high-dose group, and no teratogenic effects were found in any dose group. 4.4.4. Genotoxicity Propionitrile (0.03 to 30 μmol/plate) did not induce reverse mutations ei- ther with or without metabolic activation (S-9 fraction) in Salmonella typhi- murium strains TA98, TA100, TA1535, or TA1537. It was also negative in Escherichia coli strain Sd-4-73 when tested at concentrations of 0.01-0.025 mL/plate (EPA 1985). Propionitrile induced mitotic chromosome loss in Sac- 

Aliphatic Nitriles 65 chromyces cerevisiae strain D61.M (Whittaker et al. 1989) and mitotic chromo- some gain in strain BR1669 (Whittaker et al. 1990). Sex chromosome aneu- ploidy was induced in oocytes of female Drosophila melanogaster fed propi- onitrile as larvae or as adults (Osgood et al. 1991). Propionitrile may interfere with tubulin assembly in vitro, thereby inducing chromosome malsegregation with no effect on recombination or mutation. Propionitrile was negative for sis- ter chromatid exchanges and chromosome aberrations both with and without metabolic activation in cultured Chinese hamster ovary cells (Loveday et al. 1990). 4.4.5. Carcinogenicity No information concerning the carcinogenicity of propionitrile was found. 4.4.6. Summary Rats and mice exposed to propionitrile exhibited signs of toxicity con- sistent with cyanide poisoning. A 4-h rat LC50 of 1,441 ppm (Younger Labs 1978) and a 1-h mouse LC50 of 163 ppm (Willhite 1981) were calculated. Sub- cutaneous administration of propionitrile induced duodenal ulcers in rats. No reproductive or developmental toxicity was found in the absence of maternal toxicity. Genotoxicity data were generally negative, except for chromosome loss or gain. No carcinogenicity data on propionitrile were found. 4.5. Data Analysis for AEGL-1 4.5.1. Human Data Relevant to AEGL-1 No human data on propionitrile consistent with the definition of AEGL-1 were available. 4.5.2. Animal Data Relevant to AEGL-1 No animal data on propionitrile consistent with the definition of AEGL-1 were available. 4.5.3. Derivation of AEGL-1 Values Chemical-specific data were insufficient to derive AEGL-1 values for propionitrile. Because the available data do not suggests a particularly steep concentration-response curve for this chemical, it was considered inappropriate to estimate AEGL-1 values by dividing the AEGL-2 values by 3. Therefore, AEGL-1 values are not recommended for propionitrile. 

66 Acute Exposure Guideline Levels 4.6 Data Analysis for AEGL-2 4.6.1. Human Data Relevant to AEGL-2 A worker exposed to propionitrile at approximately 34 ppm for 2 h experi- enced headache, nausea, and dizziness (Scolnick et al. 1993). After leaving the work area, he vomited and was found confused and disoriented 5 h later. 4.6.2. Animal Data Relevant to AEGL-2 No animal data on propionitrile consistent with the definition of AEGL-2 were available. 4.6.3. Derivation of AEGL-2 Values The headache, nausea, and dizziness reported in the worker exposed to propionitrile at approximately 34 ppm for 2 h are considered AEGL-2 level ef- fects. However, because a no-effect level was not identified, these data are not appropriate for deriving AEGL-2 values. Therefore, AEGL-2 values were de- rived by dividing the AEGL-3 values by 3 (NRC 2001). The AEGL-2 values for propionitrile are presented in Table 1-22. These values are below the concentra- tion of 34 ppm (2-h exposure) shown to produce disabling effects in an exposed worker (Scolnick et al. 1993). 4.7. Data Analysis for AEGL-3 4.7.1. Human Data Relevant to AEGL-3 No human data on propionitrile consistent with the definition of AEGL-3 were available. 4.7.2. Animal Data Relevant to AEGL-3 Saillenfait et al. (1993) observed maternal deaths in pregnant rats exposed to propionitrile at 200 ppm for 6 h/day on days 6-20 of gestation. An increase in the incidences of nonsurviving implants and embryonic resorptions was ob- served at 200 ppm compared with controls, and a concentration-related decrease in fetal weights was also observed in the offspring of the 200-ppm group. No maternal deaths or developmental effects were observed at 150 ppm. A 4-h LC50 of 1,441 ppm was calculated for Sprague-Dawley rats (Younger Labs 1978). The highest concentration causing no mortality was 690 ppm. A 1-h LC50 of 163 ppm was calculated for male CD-1 mice (Willhite 1981). No concentration- response data were available for this study. 

Aliphatic Nitriles 67 TABLE 1-22 AEGL-2 Values for Propionitrile 10 min 30 min 1h 4h 8h 3.7 ppm 3.7 ppm 3.0 ppm 1.9 ppm 1.3 ppm (8.3 mg/m3) (8.3 mg/m3) (6.8 mg/m3) (4.3 mg/m3) (2.9 mg/m3) 4.7.3. Derivation of AEGL-3 Values The threshold level for maternal mortality and increased fetal resorptions in pregnant rats exposed to propionitrile at 150 ppm for 6 h/day on gestational days 6-20 (Saillenfait et al. 1993) was used as the point of departure for deriving AEGL-3 values for propionitrile. Although the study involved repeated expo- sures, fetal death can occur during a narrow developmental window and does not necessarily require repeated exposures (Van Raaij et al. 2003). Therefore, the observation of increased fetal resorptions following repeated gestational ex- posure is considered a relevant end point for AEGL-3 values. The no-effect lev- el of 150 ppm for fetal death was the point of departure. An intraspecies uncer- tainty factor of 3 was applied because studies of accidental and occupational exposures to hydrogen cyanide (the metabolically-liberated toxicant) indicate that there are individual differences in sensitivity to this chemical but that the differences are not expected to exceed 3-fold (NRC 2002). An interspecies un- certainty factor of 10 was also applied because no comparable studies of similar exposures (repeated inhalation exposure during gestation) in other species were available. Thus, the total uncertainty factor is 30. Time scaling was performed using the equation Cn × t = k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). This equation has been shown to describe the concentration- exposure duration relationship for many irritant and systemically acting vapors and gases. Data on propionitrile were insufficient for deriving an empirical value for n. Therefore, default values of n = 3 to extrapolate to shorter durations (30 min, 1h, and 4 h) and n = 1 to extrapolate longer durations (8-h) were used to estimate AEGL values that are protective of human health (NRC 2001). The 10- min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with time scaling a 6-h exposure to a 10-min value. AEGL-3 values for propionitrile are presented in Table 1-23, and the calcula- tions are presented in Appendix B. 4.8. Summary of AEGLs 4.8.1. AEGL Values and Toxicity End Points AEGL values for propionitrile are presented in Table 1-24. Data were in- sufficient to derive AEGL-1 values. Data were also insufficient for AEGL-2 values, so values were estimated by dividing the AEGL-3 values by 3. A no- effect level for maternal mortality and increased fetal resorptions in pregnant rats exposed to propionitrile on gestational days 6-20 was used as the basis for the AEGL-3 values. 

68 Acute Exposure Guideline Levels TABLE 1-23 AEGL-3 Values for Propionitrile 10 min 30 min 1h 4h 8h 11 ppm 11 ppm 9.1 ppm 5.7 ppm 3.8 ppm (25 mg/m3) (25 mg/m3) (20 mg/m3) (13 mg/m3) (8.6 mg/m3) TABLE 1-24 AEGL Values for Propionitrile Classification 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa (nondisabling) AEGL-2 3.7 ppm 3.7 ppm 3.0 ppm 1.9 ppm 1.3 ppm (disabling) (8.3 mg/m3) (8.3 mg/m3) (6.8 mg/m3) (4.3 mg/m3) (2.9 mg/m3) AEGL-3 11 ppm 11 ppm 9.1 ppm 5.7 ppm 3.8 ppm (lethal) (25 mg/m3) (25 mg/m3) (20 mg/m3) (13 mg/m3) (8.6 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 4.8.2. Other Standards and Guidelines Only one other exposure standard for propionitrile was found (see Table 1-25). The National Institute for Occupational Safety and Health’s recommend- ed exposure limit (time-weighted average) of 6 ppm is based on evidence that selected nitrile compounds are metabolized to cyanide ion, which causes numer- ous systemic effects. 4.8.3. Data Adequacy and Research Needs Data were insufficient to derive AEGL-1 values for propionitrile. Data were also insufficient for AEGL-2 values, so they had to be estimated from the AEGL-3 values. Only limited animal data were available from which to derive AEGL-3 values. 5. CHLOROACETONITRILE 5.1. Summary Chloroacetonitrile is a colorless liquid at ambient temperature and pres- sure. It has a pungent odor and may cause irritation or burning of the eyes, skin, and respiratory tract. It is metabolized to cyanide in the body and signs of intox- ication may include weakness, headache, dizziness, confusion, nausea, vomiting, convulsion, dilated pupils, weak pulse, tachypnea, dyspnea, and cyanosis (HSDB 2013). 

Aliphatic Nitriles 69 TABLE 1-25 Standards and Guidelines for Propionitrile Exposure Duration Guideline 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa AEGL-2 3.7 ppm 3.7 ppm 3.0 ppm 1.9 ppm 1.3 ppm (8.3 mg/m3) (8.3 mg/m3) (6.8 mg/m3) (4.3 mg/m3) (2.9 mg/m3) AEGL-3 11 ppm 11 ppm 9.1 ppm 5.7 ppm 3.8 ppm (25 mg/m3) (25 mg/m3) (20 mg/m3) (13 mg/m3) (8.6 mg/m3) REL-TWA – – – – 6 ppm (NIOSH)b (14 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. b REL-TWA (recommended exposure limit - time-weighted average, National Institute for Occupational Safety and Health) (NIOSH 2011c) is defined as a time-weighted average concentrations for up to a 10-h workday during a 40-h workweek. Chemical-specific inhalation data on chloroacetonitrile were insufficient for deriving AEGL values. Therefore, a relative potency approach was used to estimate AEGL-2 and AEGL-3 values for chloroacetonitrile on the basis of comparison with acetonitrile. In the absence of inhalation data on chloroacetoni- trile, comparison was based on the intraperitoneal toxicity of the two chemicals. Intraperitoneal LD50 data from studies of mice suggest that, on a molar basis, chloroacetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1-1). Therefore, AEGL-2 and AEGL-3 values for acetonitrile were divid- ed by 10 to approximate AEGL-2 and AEGL-3 values for chloroacetonitrile. AEGL-1 values were not derived by this method because of the uncertainty as- sociated with applying a relative potency estimate based on lethality to AEGL-1 effects. AEGL values for malononitrile are presented in Table 1-26. 5.2. Introduction Chloroacetonitrile is a colorless liquid at ambient temperature and pres- sure. It has a pungent odor and may cause irritation or burning of the eyes, skin, and respiratory tract. Chloroacetonitrile is produced commercially by the high-temperature chlorination of acetonitrile (IARC 1991). It has been used as a fumigant and is an organic intermediate in the manufacture of the insecticide fenoxycarb and the cardiovascular drug guanethidine. Occupational exposure to chloroacetonitrile may occur via inhalation or dermal contact at workplaces where chloroacetoni- trile is used or produced (HSDB 2013). Halogenated acetonitriles have been detected in chlorinated drinking water in several countries as a result of the reac- tion of chlorine with natural organic substances present in untreated water (IARC 1999). The chemical and physical properties of chloroacetonitrile are presented in Table 1-27. 

70 Acute Exposure Guideline Levels TABLE 1-26 AEGL Values for Chloroacetonitrile Classification 10 min 30 min 1h 4h 8h End point (Reference) AEGL-1 NRa NRa NRa NRa NRa Insufficient data (nondisabling) AEGL-2 8.0 ppm 8.0 ppm 5.0 ppm 2.1 ppm 1.4 ppm Based on AEGL-2 (disabling) (25 (25 (15 (6.5 (4.3 values for acetonitrile mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) AEGL-3 24 ppm 24 ppm 15 ppm 6.4 ppm 4.2 ppm Based on AEGL-3 (lethal) (74 (74 (46 (20 (13 values for acetonitrile mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) a Not recommended. Sbsence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. TABLE 1-27 Chemical and Physical Data on Chloroacetonitrile Parameter Data Reference Common name Chloroacetonitrile HSDB 2013 Synonyms Monochloromethyl cyanide; HSDB 2013 monochloroacetonitrile; chloromethyl cyanide CAS registry no. 107-14-2 HSDB 2013 Chemical formula C2H2ClN HSDB 2013 Molecular weight 75.50 HSDB 2013 Physical state Colorless liquid HSDB 2013 Boiling point 126.5°C HSDB 2013 Density/Specific gravity 1.1930 at 20°C HSDB 2013 5 Solubility In water, >1 × 10 mg/L (temperature HSDB 2013 not specified); soluble in hydrocarbons and alcohols Vapor density 2.61 (air = 1) HSDB 2013 Vapor pressure 8 mm Hg at 20°C HSDB 2013 3 Conversion factors in air 1 ppm = 3.09 mg/m 1 mg/m3 = 0.323 ppm 5.3. Human Toxicity Data 5.3.1. Acute Lethality Information concerning death in humans following inhalation exposure to chloroacetonitrile is not available. 

Aliphatic Nitriles 71 5.3.2. Nonlethal Toxicity Information concerning nonlethal toxicity in humans following inhalation exposure to chloroacetonitrile is not available. 5.3.3. Developmental and Reproductive Toxicity Developmental and reproductive studies of acute human exposure to chlo- roacetonitrile were not available. 5.3.4. Genotoxicity Genotoxicity studies of acute human exposure to chloroacetonitrile were not available. 5.3.5. Carcinogenicity Carcinogenicity studies of human exposure to chloroacetonitrile were not available. 5.4.6. Summary No human studies of the lethal toxicity, nonlethal toxicity, developmental or reproductive toxicity, genotoxicity, or carcinogenicity of chloroacetonitrile were available. 5.4. Animal Toxicity Data 5.4.1. Acute Lethality 5.4.1.1. Rats Groups of two or three male and two or three female Sprague-Dawley rats were administered single doses of chloroacetonitrile at 126, 158, 200, or 251 mg/kg by gavage and observed for up to 14 days (Younger Labs 1976). De- creased appetite and activity (1-2 days in survivors), increasing weakness, trem- ors, convulsions, collapse, and death were observed in the three highest dose groups. Lung hyperemia, slight liver discoloration, and gastrointestinal inflam- mation were found in decedents at necropsy. Surviving rats had no abnormal findings at necropsy. Mortality incidence was 0/5 at 126 mg/kg, 2/5 at 158 mg/kg, 4/5 at 200 mg/kg, and 5/5 at 251 mg/kg. An LD50 for chloroacetonitrile of 180 mg/kg was calculated. An oral LD50 of 220 mg/kg for rats was reported (Lewis 1996). No further information was available. 

72 Acute Exposure Guideline Levels 5.4.1.2. Mice The oral LD50 for chloroacetonitrile was estimated to be 139 mg/kg in male ddY mice (Tanii and Hashimoto 1984). An intraperitoneal LD50 of 100 mg/kg for mice was reported (Lewis 1996). No further information was available. 5.4.1.3. Rabbits One or two New Zealand white rabbits were administered single 24-h dermal doses of chloroacetonitrile at 100, 158, 200, 251, or 376 mg/kg and ob- served for up to 14 days (Younger Labs 1976). Decreased appetite and activity (2-3 days in survivors), rapidly increasing weakness, tremors, convulsions, dyspnea, collapse, and death were observed in the three highest dose groups. Hemorrhagic lungs, liver, and spleen, kidney discoloration, ruptured gall blad- ders, and gastrointestinal inflammation were found in decedents at necropsy. Surviving rabbits had no abnormal findings at necropsy. Mortality incidence was 0/1 at 100 mg/kg, 0/1 at 158 mg/kg, 2/2 at 200 mg/kg, 1/1 at 251 mg/kg, and 1/1 at 376 mg/kg. Younger Labs (1976) reported that chloroacetonitrile was corrosive to the eyes of New Zealand white rabbits. 5.4.2. Nonlethal Toxicity No information concerning the nonlethal toxicity of chloroacetonitrile in animals was available. 5.4.3. Developmental and Reproductive Toxicity Thirty pregnant Long-Evans rats were administered chloroacetonitrile at 55 mg/kg by gavage on days 7-21 of gestation (Smith et al. 1987). The litters were culled to six to eight pups on postnatal day 6 and were further culled to four pups at weaning. These pups were observed until 41-42 days of age. One of the treated dams died, and there was a decrease in maternal weight gain (13% decrease; p < 0.05) during treatment. There was no effect on pregnancy, resorp- tions, pup survival, or pup growth after birth. Litter weight at birth was de- creased (8% decrease; p < 0.05) compared with controls. 5.4.4. Genotoxicity Chloroacetonitrile at concentrations of 5.0-160 μmol/plate did not induce reverse mutations either with or without metabolic activation (S-9 fraction) in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 (Bull et 

Aliphatic Nitriles 73 al. 1985). Similar results were obtained when the chemical was tested at concen- trations of 10-3,333 μg/plate (Mortelmans et al. 1986). Chloroacetonitrile at concentrations of 15.8-950 μM was negative in a sister chromatid exchange as- say using Chinese hamster ovary cells with metabolic activation, and was posi- tive without metabolic activation at concentrations of 52-158 μM (Bull et al. 1985). Micronuclei were induced in the erythrocytes of newt larvae exposed for 12 days to chloroacetonitrile at 1.25-5 μg/mL (LeCurieux et al. 1995); however, mice administered chloroacetonitrile for 5 days had neither micronuclei in bone marrow (Bull et al. 1985) nor abnormal sperm morphology at doses of 12.5, 25, or 50 mg/kg/day (Meier et al. 1985). Chloroacetonitrile at 3 mM was weakly positive in a DNA strand break assay in cultured human lymphoblastic cells (Daniel et al. 1986). 5.4.5. Carcinogenicity Groups of 10-week-old female A/J mice were administered chloroacetoni- trile at 10 mg/kg in 10% Emulphor by gavage three times per week for 8 weeks (Bull and Robinson 1985). A control group of 40 mice were treated with 10% Emulphor. Survival at the end of the study was 31/40 for controls and 28/40 for the chloroacetonitrile-treated animals. Lung adenomas occurred in 3/31 control animals and 9/28 treated animals; the average numbers of tumors per mouse were 0.1 for controls and 0.43 for mice administered chloroacetonitrile. In an initiation-promotion study, groups of 40 female Sencar mice were treated dermally with chloroacetonitrile at 200, 400, or 800 mg/kg in 0.2 mL of acetone three times per week for 2 weeks (Bull et al. 1985). Three groups of 40 mice served as controls and were treated with only acetone. Two weeks after the last chloroacetonitrile application, mice were treated topically with 12-O- tetradecanoylphorbol 13-acetate (TPA) at 1 μg three times per week for 20 weeks. Animals were observed for 1 year. Combined incidences of papillomas and carcinomas was 11/38 in the low-dose group (p < 0.001), 11/37 in the mid- dose group (p < 0.01), and 6/38 in the high-dose group. Incidences were 1/34, 3/37, and 5/34 for the three control groups. In another experiment, groups of 40 female Sencar mice were treated der- mally with chloroacetonitrile at 800 mg/kg in 0.2 mL of acetone three times per week for 24 weeks (Bull et al. 1985). A group of 40 mice served as a control and were treated with only acetone. No tumors were observed; however, the duration of the observation period was not stated. 5.4.6. Summary Inhalation toxicity data for chloroacetonitrile were not available, and other animal toxicity data are sparse. Animals exposed to chloroacetonitrile by oral and dermal routes exhibited signs consistent with cyanide poisoning. Rat oral LD50 values of 180 mg/kg (Younger Labs 1976) and 200 mg/kg (Lewis, 1996) 

74 Acute Exposure Guideline Levels have been reported. In mice, an oral LD50 of 139 mg/kg (Tanii and Hashimoto 1984) and an intraperitoneal LD50 of 100 mg/kg were reported (Lewis 1996). No reproductive or developmental toxicity was noted in rats in the absence of ma- ternal toxicity. Genotoxicity data were equivocal. An increase in the incidence of lung adenomas was found in mice treated orally with chloroacetonitrile; how- ever, IARC (1991) concluded that there is inadequate evidence of carcinogenici- ty of chloroacetonitrile in experimental animals. 5.5. Special Considerations 5.5.1. Other Available Data Little data are available to evaluate the toxicity of chloroacetonitrile. Chlo- roacetonitrile is oxidized in vitro to cyanide in the presence of a myeloperoxi- dase/hydrogen peroxide/chloride (Abdel-Naim and Mohamadin 2004), which provides data to support a common mechanism of toxicity for chloroacetonitrile and other aliphatic nitriles (e.g., metabolic release of cyanide; see Section 1.2). Oxidation of chloroacetonitrile to cyanide also has been demonstrated in vivo in rats following oral administration (Lin et al. 1986). Results of an oral gestational exposure study in rats show increased fetal resorptions and alterations in skeletal development in dams exposed at 50 mg/kg on gestational days 6-18 (Ahmed et al. 2008). Results are consistent with findings of gestational exposure studies on acetonitrile (see Section 2.4.3), isobutyronitrile (see Section 3.4.3), and propi- onitrile (see Section 4.4.3), in which rats were exposed via inhalation on gesta- tional days 6-20. Distribution of chloroacetonitrile to fetal tissues was demon- strated following a single intravenous administration of 14C-labeled chloroacetonitrile to pregnant rats on gestational day 13 (Jacob et al. 1998). 5.6. Data Analysis for AEGL-1 5.6.1. Human Data Relevant to AEGL-1 No human data on chloroacetonitrile consistent with the definition of AEGL-1 were available. 5.6.2. Animal Data Relevant to AEGL-1 No animal data on chloroacetonitrile consistent with the definition of AEGL-1 were available. 5.6.3. Derivation of AEGL-1 Values Chemical-specific data were insufficient for deriving AEGL-1 values for chloroacetonitrile. Therefore, AEGL-1 values are not recommended. 

Aliphatic Nitriles 75 5.7. Data Analysis for AEGL-2 5.7.1. Human Data Relevant to AEGL-2 No human data on chloroacetonitrile consistent with the definition of AEGL-2 were available. 5.7.2. Animal Data Relevant to AEGL-2 No animal data on chloroacetonitrile consistent with the definition of AEGL-2 were available. 5.7.3. Derivation of AEGL-2 Values Chemical-specific inhalation data were insufficient to derive AEGL-2 val- ues for chloroacetonitrile. However, data from other routes of exposure (oral, intraperitoneal, and dermal) are available. A relative potency approach was used to approximate AEGL-2 values for chloroacetonitrile on the basis of comparison with acetonitrile. In the absence of inhalation data, the intraperitoneal route is considered the most appropriate for approximating inhalation toxicity values because both routes involve entry into the organism through a semipermeable membrane (per- itoneal membrane and alveolar membrane) before diffusion into the blood. Fur- thermore, the magnitude and rate of effect for the different routes of administra- tion (in descending order) are: intraveneous, inhalation, intraperitoneal, subcutaneous, intramuscular, intradermal, oral, and topical (Eaton and Gilbert 2008). Intraperitoneal toxicity data are available for acetonitrile and propionitrile for comparison, but a judgment was made to use acetonitrile because the overall database on this chemical is more robust (includes toxicity data and data to de- rive a value for the exponent “n” for time scaling) than for propionitrile. Intra- peritoneal LD50 data from studies of mice suggest that, on a molar basis, chloro- acetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1- 1). Therefore, the AEGL-2 values for acetonitrile were divided by 10 to approx- imate the AEGL-2 values for chloroactonitrile. The AEGL-2 values for chloro- acetonitrile are presented in Table 1-28. 5.8. Data Analysis for AEGL-3 5.8.1. Human Data Relevant to AEGL-3 No human data on chloroacetonitrile consistent with the definition of AEGL-3 were available. 

76 Acute Exposure Guideline Levels TABLE 1-28 AEGL-2 Values for Chloroacetonitrile 10 min 30 min 1h 4h 8h 8.0 ppm 8.0 ppm 5.0 ppm 2.1 ppm 1.4 ppm (25 mg/m3) (25 mg/m3) (15 mg/m3) (6.5 mg/m3) (4.3 mg/m3) 5.8.2. Animal Data Relevant to AEGL-3 No animal data on chloroacetonitrile consistent with the definition of AEGL-3 were available. 5.8.3. Derivation of AEGL-3 Values Chemical-specific inhalation data were insufficient to derive AEGL-3 val- ues for chloroacetonitrile. Therefore, the relative-potency approach used to de- rive AEGL-2 values (described in Section 5.7.3) was also used to estimate AEGL-3 values. Because chloroacetonitrile is estimated to be approximately 10 times more toxic than acetonitrile, the AEGL-3 values for acetonitrile were di- vided by 10 to approximate AEGL-3 values for chloroacetonitrile. The AEGL-3 values for chloroacetonitrile are presented in Table 1-29. 5.9. Summary of AEGLs 5.9.1. AEGL Values and Toxicity End Points Chemical-specific data were insufficient for deriving AEGL values for chloroacetonitrile. Therefore, AEGL-2 and AEGL-3 values were determined on the basis of chloroacetonitrile’s relative potency to acetonitrile. AEGL-1 values were not derived by this method because of the uncertainty associated with ap- plying a relative-potency estimate based on lethality to effects defined by AEGL-1. The AEGL values for chloroacetonitrile are presented in Table 1-30. 5.9.2. Other Standards and Guidelines No other standards or guidelines for chloroacetonitrile were found. 5.9.3. Data Adequacy and Research Needs Chemical-specific data were insufficient to derive AEGL values for chlo- roacetonitrile. AEGL-2 and AEGL-3 values for chloroacetonitrile were deter- mined on the basis of its relative potency to acetonitrile. 

Aliphatic Nitriles 77 TABLE 1-29 AEGL-3 Values for Chloroacetonitrile 10 min 30 min 1h 4h 8h 24 ppm 24 ppm 15 ppm 6.4 ppm 4.2 ppm (74 mg/m3) (74 mg/m3) (46 mg/m3) (20 mg/m3) (13 mg/m3) TABLE 1-30 AEGL Values for Chloroacetonitrile Classification 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa (nondisabling) AEGL-2 8.0 ppm 8.0 ppm 5.0 ppm 2.1 ppm 1.4 ppm (disabling) (25 mg/m3) (25 mg/m3) (15 mg/m3) (6.5 mg/m3) (4.3 mg/m3) AEGL-3 24 ppm 24 ppm 15 ppm 6.4 ppm 4.2 ppm (lethal) (74 mg/m3) (74 mg/m3) (46 mg/m3) (20 mg/m3) (13 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. 6. MALONONITRILE 6.1. Summary Malononitrile is a white powder at ambient temperature and pressure, and can cause irritation or burning of the eyes and skin. It is metabolized to cyanide in the body and signs of intoxication may include weakness, headache, dizzi- ness, confusion, nausea, vomiting, convulsion, dilated pupils, weak pulse, tach- ypnea, dyspnea, and cyanosis. The systemic toxicity of malononitrile is due to the metabolic release of cyanide and the onset of symptoms may be delayed for up to several hours (HSDB 2003b). Chemical-specific inhalation data were insufficient to derive AEGL values for malononitrile. Therefore, a relative potency approach was used to estimate AEGL-2 and AEGL-3 values for malononitrile on the basis of comparison with acetonitrile. In the absence of inhalation data on malononitrile, comparison was based on the intraperitoneal toxicity of the two chemicals. Intraperitoneal LD50 data from studies of mice suggest that, on a molar basis, malononitrile is approx- imately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the AEGL-2 and AEGL-3 values for acetonitrile were divided by 65 to approximate AEGL-2 and AEGL-3 values for malononitrile. AEGL-1 values were not de- rived by this method because of the uncertainty associated with applying a rela- tive potency estimate based on lethality to AEGL-1 effects. The AEGL values for malononitrile are presented in Table 1-31. 6.2. Introduction Malononitrile is a white powder at ambient temperature and pressure and can cause irritation or burning of the eyes and skin. The systemic toxicity of malononitrile is due to the metabolic release of cyanide and the onset of symp- toms may be delayed for up to several hours (HSDB 2003b). 

78 Acute Exposure Guideline Levels TABLE 1-31 AEGL Values for Malononitrile End Point Classification 10 min 30 min 1h 4h 8h (Reference) AEGL-1 NRa NRa NRa NRa NRa Insufficient data (nondisabling) AEGL-2 1.2 ppm 1.2 ppm 0.77 ppm 0.32 ppm 0.22 ppm Based on AEGL-2 (disabling) (3.3 (3.3 (2.1 (0.87 (0.59 values for mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) acetonitrile AEGL-3 3.7 ppm 3.7 ppm 2.3 ppm 0.98 ppm 0.65 ppm Based on AEGL-3 (lethal) (10 (10 (6.2 (2.7 (1.7 values for mg/m3) mg/m3) mg/m3) mg/m3) mg/m3) acetonitrile a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. Malononitrile is produced batchwise by elimination of water from cyano- acetamide with phosphorus pentachloride, and can also be produced from chlo- ronitrile, methylnitrile, hydrogen cyanide, cyanochloride, and acetonitrile at temperatures above 700°C. Malononitrile is the hydrolysis product of 2- chlorobenzylizene (CS-tear gas) used for self-defense. It is used as a lubricating oil additive, and in the synthesis of thiamine, anticancer agents, acrylic fibers, and dyes (HSDB 2003b). HSDB (2003b) reported that approximately 1,200 workers were potential- ly exposed to malononitrile in 1981-1983, and that occupational exposure may occur by dermal contact. The chemical and physical properties of malononitrile are presented in Table 1-32. 6.3. Human Toxicity Data 6.3.1. Acute Lethality Information concerning death in humans following inhalation exposure to malononitrile was not available. 6.3.2. Nonlethal Toxicity 6.3.2.1. Case Reports In the late 1940s malononitrile was used as an experimental treatment for schizophrenia and depression. The premise was that malononitrile might stimu- late the formation of proteins and polynucleotides in nerve tissue and thus re- store normal function. Hyden and Hartelius (1948) administered a 5% malono- nitrile solution intravenously to 66 patients at doses of 1-6 mg/kg. The number of doses administered to each patient varied from 3 to 17; injections were made two or three times per week. Each infusion lasted from 10 to 60 min. Tachycar- 

Aliphatic Nitriles 79 dia was noted 10-20 min after infusion of malononitrile in all 66 patients. Facial redness, nausea, vomiting, shivering, cold hands and feet, muscle spasms, and numbness were also reported. Convulsions occurred in two patients. Cardiac collapse occurred in one patient with a history of congenital heart defect. Har- telius (1950) then administered a 5% malononitrile solution intravenously at an average dose of 2.4 mg/kg to nine patients. The number of doses administered to each patient varied from 3 to 12, over a period of 24 days. Each infusion lasted 48 min. Facial redness, tachycardia, and congestive flow of blood to the head were observed throughout treatment. MacKinnon et al. (1949) administered a 5% malononitrile solution intra- venously at a dose of 2 mg/kg to nine patients. Patients received 10 doses over 2-3 weeks. Clinical signs were similar to those described above; however, no convulsions occurred. Nausea recurred several hours after treatment. Myers et al. (1950) administered a 5% malononitrile solution intravenous- ly to 66 patients at doses ranging from 3 to 6 mg/kg. Each infusion lasted from 21 to 60 min. Effects during treatment included flushing of the face (appearing within 5 min and increasing throughout treatment), tachycardia (appearing with 10-15 min), nausea (appearing within 20-25 min), and vomiting (appearing within 30 min). Patients were described as restless and acutely distressed. Veins of the head and neck were distended and extremities were cold. Systolic blood pressure was increased and pulse was decreased. TABLE 1-32 Chemical and Physical Data on Malononitrile Parameter Data Reference Common name Malononitrile HSDB 2003b Synonyms Methylene cyanide; propanedinitrile; HSDB 2003b cyanoacetonitrile; dicyanomethane; malonic acid dinitrile; malonicdinitrile CAS registry no. 109-77-3 HSDB 2003b Chemical formula C3H2N2 HSDB 2003b Molecular weight 66.06 HSDB 2003b Physical state White powder HSDB 2003b Melting point 32°C HSDB 2003b Boiling point 218-219°C HSDB 2003b Density/specific gravity 1.19 at 20°C/4°C HSDB 2003b 5 Solubility In water, 1.33 × 10 mg/L at 25°C; HSDB 2003b soluble in acetone, benzene, chloroform Vapor pressure 0.200 mm Hg at 22°C HSDB 2003b 3 Conversion 1 ppm = 2.70 mg/m NIOSH 2011d 

80 Acute Exposure Guideline Levels 6.3.3. Developmental and Reproductive Toxicity Developmental and reproductive toxicity studies of acute human exposure to malononitrile were not available. 6.3.4. Genotoxicity Genotoxicity studies of acute human exposure to malononitrile were not available. 6.3.5. Carcinogenicity Carcinogenicity studies of human exposure to malononitrile were not available. 6.3.6. Summary The only human studies available on malononitrile involved the intrave- nous administration of malononitrile as an experimental treatment for mental illness. Clinical signs included tachycardia, facial redness, headache, nausea, vomiting, cold extremities, muscle spasms, and convulsions. No human studies on the developmental or reproductive toxicity, genotoxicity, or carcinogenicity of malononitrile were available. 6.4. Animal Toxicity Data 6.4.1. Acute Lethality 6.4.1.1. Rats American Cyanamid (1988) reported a 2-h LC50 of 57 ppm for rats. No de- tails of the experiment were available, and the reported value could not be veri- fied. Hicks (1950) administered intraperitoneal injections of malononitrile at 5- 10 mg/kg to 26 young adult rats at 2-4 h intervals for 1-2 days. Four rats died during the exposure period, and 15 of the surviving rats had brain lesions, in- cluding necrosis of instriatal neurons, demyelinating lesions of the optic tract and nerve, and lesions of the cerebral cortex, at necropsy. Renal tubular necro- sis, ventricular myocardial changes, and pulmonary edema were also found in some rats. 

Aliphatic Nitriles 81 6.4.1.2. Mice Panov (1969) exposed groups of six mice (strain and sex not specified) to malononitrile at 3-110 ppm for 2 h in a dynamic chamber at 29-30°C. The con- centration of malononitrile was measured colorimetrically twice during the ex- periment. Mice developed signs of restlessness and increased respiration rates shortly after exposure, followed by lassitude, cyanosis, decreased respiration rate, incoordination, trembling, and convulsions. Death occurred in two mice. Fifty percent of mice exposed to malononitrile at 74-110 ppm for 2 h died. Mice exposed at 89 ppm for 2 h developed hyperemia, had increased lung, kid- ney, and brain weights, and had decreased liver weight compared to air-exposed controls. No further details were provided (Panov1969). Mice administered a single oral dose of malononitrile at 5 mg/kg showed “general intoxication”, but no deaths occurred. Morality was 60-80% in mice administered malononitrile at single oral doses of 20-30 mg/kg, and 100% died when administered 40-50 mg/kg (Panov 1969). An LD50 of 18.6 mg/kg was cal- culated. No further experimental details were available. An intraperitoneal LD50 of 13 mg/kg was reported for mice (Lewis 1996). No further information was available. 6.4.1.3. Rabbits Panov(1969) administered a 5% malononitrile solution to the eyes of six rabbits. Tearing, hyperemia of the conjunctiva, and spasm and swelling of the eyelids occurred in all rabbits. Respiratory impairment, convulsions, and death occurred in four of the rabbits. 6.4.2. Nonlethal Toxicity Panov (1970) exposed groups of 10 rats (strain and sex not specified) to malononitrile at 0 or 13 ppm for 2 h/day for 35 days in a dynamic chamber at 29-30°C. The concentration of malononitrile was measured at 2-day intervals by determining the amount of nitrogen with Nessler reagent. Effects observed in treated animals included increased relative lung weights at the end of the study, increased reticulocyte counts on day 7 (34 in treated group vs. 14.1 in control group) and day 35 (27.9 in treated group vs. 10.3 control group), and increased respiration. 6.4.2.1. Mice Panov (1969) reported that a single dermal application of malononitrile (concentration and duration not reported) to the tails of mice (number, sex, and strain not stated) resulted in restlessness, rapid respiration, and slight cyanosis of 

82 Acute Exposure Guideline Levels the mucosa of the lips and extremities. The symptoms reportedly subsided fol- lowing removal of the chemical by washing. 6.4.3. Developmental and Reproductive Toxicity No information concerning the developmental or reproductive toxicity of malononitrile was available. 6.4.4. Genotoxicity No information concerning the genotoxicity of malononitrile was available. 6.4.5. Carcinogenicity No information concerning the carcinogenicity of malononitrile was avail- able. 6.4.6. Summary The few animal toxicity studies on malononitrile suggest that the chemical can produce central nervous system, respiratory, and cardiovascular effects in animals; however, no quantitative inhalation data were available. No studies of the reproductive developmental toxicity, genotoxicity, or carcinogenicity of malononitrile were found. 6.5. Data Analysis for AEGL-1 6.5.1. Human Data Relevant to AEGL-1 No human data on malononitrile consistent with the definition of AEGL-1 were available. 6.5.2. Animal Data Relevant to AEGL-1 No animal data on malononitrile consistent with the definition of AEGL-1 were available. 6.5.3. Derivation of AEGL-1 Values Chemical-specific data were insufficient to derive of AEGL-1 values for malononitrile. Therefore, AEGL-1 values are not recommended. 

Aliphatic Nitriles 83 6.6. Data Analysis for AEGL-2 6.6.1. Human Data Relevant to AEGL-2 No human data on malononitrile consistent with the definition of AEGL-2 were available. 6.6.2. Animal Data Relevant to AEGL-2 No animal data on malononitrile consistent with the definition of AEGL-2 were available. 6.6.3. Derivation of AEGL-2 Values Chemical-specific inhalation data were insufficient to derive AEGL-2 val- ues for malononitrile. However, data from other routes of exposure (oral and intraperitoneal) are available. A relative potency approach was used to approxi- mate AEGL-2 values for malononitrile on the basis of comparison with acetoni- trile. In the absence of inhalation data, the intraperitoneal route is considered the most appropriate for approximating inhalation toxicity values because both routes involve entry into the organism through a semipermeable membrane (peritoneal membrane and alveolar membrane) before diffusion into the blood. Furthermore, the magnitude and rate of effect for the different routes of administration (in de- scending order) are: intraveneous, inhalation, intraperitoneal, subcutaneous, intra- muscular, intradermal, oral, and topical (Eaton and Gilbert 2008). Intraperitoneal toxicity data are available for acetonitrile and propionitrile for comparison, but a judgment was made to use acetonitrile because the overall database on this chemi- cal is more robust (includes toxicity data and data to derive a value for the expo- nent “n” for time scaling) than for propionitrile. Intraperitoneal LD50 data from studies of mice suggest that, on a molar basis, malononitrile is approximately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the AEGL-2 values for acetonitrile were divided by 65 to approximate the AEGL-2 values for malo- nonitrile. The AEGL-2 values for malononitrile are presented in Table 1-33. 6.7. Data Analysis for AEGL-3 6.7.1. Human Data Relevant to AEGL-3 No human data on malononitrile consistent with the definition of AEGL-3 were available. 

84 Acute Exposure Guideline Levels TABLE 1-33 AEGL-2 Values for Malononitrile 10 min 30 min 1h 4h 8h 1.2 ppm 1.2 ppm 0.77 ppm 0.32 ppm 0.22 ppm (3.3 mg/m3) (3.3 mg/m3) (2.1 mg/m3) (0.87 mg/m3) (0.59 mg/m3) 6.7.2. Animal Data Relevant to AEGL-3 A 2-h LC50 of 57 ppm for rats was reported (American Cyanamid 1988). However, no experimental details were available, and the reported value could not be verified. 6.7.3. Derivation of AEGL-3 Values Chemical-specific inhalation data were insufficient to derive AEGL-3 val- ues for malononitrile. Therefore, the relative-potency approach used to derive AEGL-2 values (described in Section 6.6.3) was also used to estimate AEGL-3 values. Because malononitrile is estimated to be approximately 65 times more toxic than acetonitrile, the AEGL-3 values for acetonitrile were divided by 65 to approximate AEGL-3 values for malononitrile. The AEGL-3 values for malono- nitrile are presented in Table 1-34. 6.8. Summary of AEGLs 6.8.1. AEGL Values and Toxicity End Points Chemical-specific data were insufficient for deriving AEGL values for malononitrile. Therefore, AEGL-2 and AEGL-3 values were determined on the basis of malononitrile’s relative potency to acetonitrile. AEGL-1 values were not derived by this method because of the uncertainty associated with applying a relative-potency estimate based on lethality to effects defined by AEGL-1. The AEGL values for malononitrile are presented in Table 1-35. 6.8.2. Other Standards and Guidelines Only one other exposure standard for malononitrile was found (see Table 1-36). The National Institute for Occupational Safety and Health’s recommend- ed exposure limit (time-weighted average) of 3 ppm is based on evidence that selected nitrile compounds are metabolized to cyanide ion, which causes numer- ous systemic effects. 

Aliphatic Nitriles 85 TABLE 1-34 AEGL-3 Values for Malononitrile 10 min 30 min 1h 4h 8h 3.7 ppm 3.7 ppm 2.3 ppm 0.98 ppm 0.65 ppm (10 mg/m3) (10 mg/m3) (6.2 mg/m3) (2.7 mg/m3) (1.7 mg/m3) TABLE 1-35 AEGL Values for Malononitrile Classification 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa (nondisabling) AEGL-2 1.2 ppm 1.2 ppm 0.77 ppm 0.32 ppm 0.22 ppm (disabling) (3.3 mg/m3) (3.3 mg/m3) (2.1 mg/m3) (0.87 mg/m3) (0.59 mg/m3) AEGL-3 3.7 ppm 3.7 ppm 2.3 ppm 0.98 ppm 0.65 ppm (lethal) (10 mg/m3) (10 mg/m3) (6.2 mg/m3) (2.7 mg/m3) (1.7 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 valued is without adverse effects. TABLE 1-36 Other Standards and Guidelines for Malononitrile Exposure Duration Guideline 10 min 30 min 1h 4h 8h AEGL-1 NRa NRa NRa NRa NRa AEGL-2 1.2 ppm 1.2 ppm 0.77 ppm 0.32 ppm 0.22 ppm (3.3 mg/m3) (3.3 mg/m3) (2.1 mg/m3) (0.87 mg/m3) (0.59 mg/m3) AEGL-3 3.7 ppm 3.7 ppm 2.3 ppm 0.98 ppm 0.65 ppm (10 mg/m3) (10 mg/m3) (6.2 mg/m3) (2.7 mg/m3) (1.7 mg/m3) REL-TWA – – – – 3 ppm (NIOSH)a (8.1 mg/m3) a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. b REL-TWA (recommended exposure limits—time-weighted average, National Institute for Occupational Safety and Health) (NIOSH 2011d) is defined as a time-weighted aver- age concentrations for up to a 10-h workday during a 40-h workweek. Values is based on relative toxicity (subcutaneous exposure) to isobutyronitrile. 6.8.3. Data Adequacy and Research Needs Chemical-specific data were insufficient to derive AEGL values for malo- nonitrile. AEGL-2 and AEGL-3 values for malononitrile were determined on the basis of its relative potency to acetonitrile. 7. REFERENCES Abdel-Naim, A.B., and A.M. Mohamadin. 2004. Myeloperoxidase-catalyzed oxidation of chloroacetonitrile to cyanide. Toxicol. Lett. 146(3):249-257. ACGIH (American Conference of Governmental Industrial Hygienists). 2012. TLVs and BEIs Based on Documentation of the Threshold Limit Values for Chemical Sub- stances and Physical Agents. ACGIH, Cincinnati, OH. 

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94 Acute Exposure Guideline Levels APPENDIX A CALCULATION OF THE TIME-SCALING EXPONENT “N” Concentration vs Time Analysis Using DoseResp TABLE A-1 Lethality in Rats After Acute Inhalation of Acetonitrile Concentration (ppm) Minutes Exposed Dead 53,000 15 6 0 53,000 30 6 3 25,000 30 3 3 4,000 240 30 3 8,000 240 30 10 32,000 240 30 17 10,100 240 10 0 13,600 240 10 1 19,700 240 10 3 22,200 240 10 8 4,000 240 24 0 8,000 240 24 3 16,000 240 24 9 32,000 240 24 24 1,000 480 24 0 2,000 480 24 1 4,000 480 24 2 8,000 480 24 7 16,000 480 24 21 32,000 480 24 24 Selection of trials from number 1 through 20 Transformation of variables Concentration ppm is transformed logaritmically! Minutes is transformed logarithmically! Probit model used without background response correction! Variable 1 = conc ppm Variable 2 = minutes Chi-Square = 67.02 Degrees of Freedom = 17 B 0 = -1.124E+01 Student t for B 0 = -3.623 B 1 = 1.225E+00 Student t for B 1 = 5.456 B 2 = 7.907E-01 Student t for B 2 = 2.932 

Aliphatic Nitriles 95 Variance B 0 0 = 9.617E+00 Covariance B 0 1 = -6.255E-01 Covariance B 0 2 = -6.557E-01 Variance B 1 1 = 5.042E-02 Covariance B 1 2 = 2.636E-02 Variance B 2 2 = 7.274E-02 The prediction of the model is not sufficient. Use for estimation of the 95% confidence limits. Student t with 17 degrees of freedom Correction for variances Chi-Squares/Degrees of Freedom = 3.943 The prediction of the model is not sufficient. Use for estimation of the 95% confidence limits Student t with 17 degrees of freedom Correction for variances Chi-Squares/Degrees of Freedom = 3.943 Student t = 2.110 Estimation of ratio between regression coefficients Ratio between regression coefficients conc ppm and minutes Ratio = 1.550 Confidence limits 0.539 2.5 

96 Acute Exposure Guideline Levels APPENDIX B DERIVATION OF AEGL VALUES FOR SELECTED ALIPHATIC NITRILES Acetonitrile Derivation of AEGL-1 Values Key study: Pozzani, U.C., C.P. Carpenter, P.E. Palm, C.S. Weil, and J.H. Nair. 1959. An investigation of the mammalian toxicity of acetonitrile. J. Occup. Med. 1:634-642. Toxicity end point: Slight chest tightness and cooling sensation in the lung reported by one of three volunteers exposed to acetonitrile at 40 ppm for 4 h. Time scaling: Value held constant across the 10-min to 4-h durations. Uncertainty factors: 1 for interspecies differences 1 for intraspecies variability Modifying factor: 3 because of the sparse database Calculations: 10-min AEGL-1: Set equal to the 4-h AEGL-1 of 13 ppm 30-min AEGL-1: Set equal to the 4-h AEGL-1 of 13 ppm 1-h AEGL-1: Set equal to the 4-h AEGL-1 of 13 ppm 4-h AEGL-1: 40 ppm ÷ 3 = 13 ppm 8-h AEGL-1: Not recommended Derivation of AEGL-2 Values In the absence of relevant data to derived AEGL-2 values for acetonitrile, AEGL-3 values were dived by 3 to estimate AEGL-2 values. 

Aliphatic Nitriles 97 Calculations: 10-min AEGL-2: 240 ppm ÷ 3 = 80 ppm 30-min AEGL-2: 240 ppm ÷ 3 = 80 ppm 1-h AEGL-2: 150 ppm ÷ 3 = 50 ppm 4-h AEGL-2: 64 ppm ÷ 3 = 21 ppm 8-h AEGL-2: 42 ppm ÷ 3 = 14 ppm Derivation of AEGL-3 Values Key study: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Toxicity end point: No-effect level for maternal and fetal lethality (1,500 ppm for 6 h/d on gestational days 6-20). Time scaling: C1.6 × t = k (1,500 ppm)1.6 × 6 h = 7.24 × 105 ppm-h Uncertainty factors: 10 for interspecies differences 3 for intraspecies variability Calculations: 10-min AEGL-3: Set equal to the 30-min AEGL-3 value of 240 ppm 30-min AEGL-3: C1.6 × 0.5 h = 7.24 × 105 ppm-h C1.6 = 1.45 × 106 ppm C = 7,089 ppm 7,089 ÷ 30 = 240 ppm 1-h AEGL-3: C1.6 × 1 h = 7.24 × 105 ppm-h C1.6 = 7.24 × 105 ppm C = 4,597 ppm 4,596 ÷ 30 = 150 ppm 4-h AEGL-3: C1.6 × 4 h = 7.24 × 105 ppm-h C1.6 = 1.81 × 105 ppm C = 1,933 ppm 1,933 ÷ 30 = 64 ppm 

98 Acute Exposure Guideline Levels 8-h AEGL-3: C1.6 × 8 h = 7.24 × 105 ppm-h C1.6 = 9.05 × 104 ppm C = 1,253 ppm 1,253 ÷ 30 = 42 ppm Isobutyronitrile Derivation of AEGL-1 Values The data on isobutyronitrile were insufficient for deriving AEGL-1 values. Derivation of AEGL-2 Values In the absence of relevant data to derived AEGL-2 values for isobutyronitrile, AEGL-3 values were dived by 3 to estimate AEGL-2 values. Calculations: 10-min AEGL-2: 7.6 ppm ÷ 3 = 2.5 ppm 30-min AEGL-2: 7.6 ppm ÷ 3 = 2.5 ppm 1-h AEGL-2: 6.1 ppm ÷ 3 = 2.0 ppm 4-h AEGL-2: 3.8 ppm ÷ 3 = 1.3 ppm 8-h AEGL-2: 2.5 ppm ÷ 3 = 0.83 ppm Derivation of AEGL-3 Values Key study: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Toxicity end point: No maternal mortality (100 ppm, 6 h/d on gestational days 6-20) Time scaling: Cn × t = k (default values of n =3 for extrapolating to shorter durations and n =1 for extrapolating to longer durations) (100 ppm)3 × 6 h = 6.00 × 106 ppm-h (100 ppm)1 × 6 h = 600 ppm-h 

Aliphatic Nitriles 99 Uncertainty factors: 10 for interspecies differences 3 for intraspecies variability Calculations: 10-min AEGL-3: Set equal to the 30-min AEGL-3 values of 7.6 ppm 30-min AEGL-3: C3 × 0.5 h = 6.0 × 106 ppm-h C3 = 1.20 × 107 ppm C = 229 ppm 229 ÷ 30 = 7.6 ppm 1-h AEGL-3: C3 × 1 h = 6.0 × 106 ppm-h C3 = 6.00 × 106 ppm C = 182 ppm 182 ÷ 30 = 6.1 ppm 4-h AEGL-3: C3 × 4 h = 6.0 × 106 ppm-h C3 = 1.50 × 106 ppm C = 114 ppm 114 ÷ 30 = 3.8 ppm 8-h AEGL-3: C1 × 8 h = 600 ppm-h C1 = 75 ppm C = 75 ppm 75 ÷ 30 = 2.5 ppm Propionitrile Derivation of AEGL-1 Values The data on propionitrile were insufficient for deriving AEGL-1 values. Derivation of AEGL-2 Values In the absence of relevant data to derived AEGL-2 values for propionitrile, AEGL-3 values were dived by 3 to estimate AEGL-2 values. Calculations: 10-min AEGL-2: 11 ppm ÷ 3 = 3.7 ppm 30-min AEGL-2: 11 ppm ÷ 3 = 3.7 ppm 1-h AEGL-2: 9.1 ppm ÷ 3 = 3.0 ppm 

100 Acute Exposure Guideline Levels 4-h AEGL-2: 5.7 ppm ÷ 3 = 1.9 ppm 8-h AEGL-2: 3.8 ppm ÷ 3 = 1.3 ppm Derivation of AEGL-3 Values Key study: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz, J. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Toxicity end point: No maternal or fetal mortality (150 ppm, 6 h/d on gestational days 6-20) Time scaling: Cn × t = k (default values of n =3 for extrapolating to shorter durations and n =1 for extrapolating to longer durations) (150 ppm)3 × 6 h = 2.03 × 107 ppm-h (150 ppm)1 × 6 h = 900 ppm-h Uncertainty factors: 10 for interspecies differences 3 for intraspecies variability Calculations: 10-min AEGL-3: Set equal to the 30-min AEGL-3 value of 11 ppm 30-min AEGL-3: C3 × 0.5 h = 2.03 × 107 ppm-h C3 = 4.05 × 107 ppm C = 343 ppm 343 ÷ 30 = 11 ppm 1-h AEGL-3: C3 × 1 h = 2.03 × 107 ppm-h C3 = 2.02 × 107 ppm C = 273 ppm 273 ÷ 30 = 9.1 ppm 4-h AEGL-3: C3 × 4 h = 2.03 × 107 ppm-h C3 = 5.06 × 106 ppm C = 172 ppm 172 × 30 = 5.7 ppm 8-h AEGL-3: C1 × 8 h = 900 ppm-h C1 = 112 ppm C = 112 ppm 112 ÷ 30 = 3.8 ppm 

Aliphatic Nitriles 101 Chloroacetonitrile Derivation of AEGL-1 Values The data on chloroacetonitrile were insufficient for deriving AEGL-1 values. Derivation of AEGL-2 Values No chemical-specific data were available to derive AEGL-2 values for chloro- acetonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloro- acetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-2 values were divided by 10 to approximate AEGL-2 values for chloroacetonitrile. Calculations: 10-min AEGL-2: 80 ppm ÷ 10 = 8.0 ppm 30-min AEGL-2: 80 ppm ÷ 10 = 8.0 ppm 1-h AEGL-2: 50 ppm ÷ 10 = 5.0 ppm 4-h AEGL-2: 21 ppm ÷ 10 = 2.1 ppm 8-h AEGL-2: 14 ppm ÷ 10 = 1.4 ppm Derivation of AEGL-3 Values No chemical-specific data were available to derive AEGL-3 values for chloro- acetonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloro- acetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-3 values were divided by 10 to approximate AEGL-2 values for chloroacetonitrile. 10-min AEGL-3: 240 ppm ÷ 10 = 24 ppm 30-min AEGL-3: 240 ppm ÷ 10 = 24 ppm 1-h AEGL-3: 150 ppm ÷ 10 = 15 ppm 4-h AEGL-3: 64 ppm ÷ 10 = 6.4 ppm 8-h AEGL-3: 42 ppm ÷ 10 = 4.2 ppm 

102 Acute Exposure Guideline Levels Malononitrile Derivation of AEGL-1 Values The data on malononitrile were insufficient for deriving AEGL-1 values. Derivation of AEGL-2 Values No chemical-specific data were available to derive AEGL-2 values for malo- nonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloroace- tonitrile is approximately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-2 values were divided by 65 to approximate AEGL-2 values for malononitrile. Calculations: 10-min AEGL-2: 80 ppm ÷ 65 = 1.2 ppm 30-min AEGL-2: 80 ppm ÷ 65 = 1.2 ppm 1-h AEGL-2: 50 ppm ÷ 65 = 0.77 ppm 4-h AEGL-2: 21 ppm ÷ 65 = 0.32 ppm 8-h AEGL-2: 14 ppm ÷ 65 = 0.22 ppm Derivation of AEGL-3 Values No chemical-specific data were available to derive AEGL-3 values for malo- nonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloroace- tonitrile is approximately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-2 values were divided by 65 to approximate AEGL-3 values for malononitrile. Calculations: 10-min AEGL-3: 240 ppm ÷ 65 = 3.7 ppm 30-min AEGL-3: 240 ppm ÷ 65 = 3.7 ppm 1-h AEGL-3: 150 ppm ÷ 65 = 2.3 ppm 4-h AEGL-3: 64 ppm ÷ 65 = 0.98 ppm 8-h AEGL-3: 42 ppm ÷ 65 = 0.65 ppm 

Aliphatic Nitriles 103 APPENDIX C ACUTE EXPOSURE GUIDELINE LEVELS FOR SELECTED ACRYLONITRILES Derivation Summary for Acetonitrile AEGL-1 Values for Acetonitrile 10 min 30 min 1h 4h 8h 13 ppm 13 ppm 13 ppm 13 ppm NRa (22 mg/m3) (22 mg/m3) (22 mg/m3) (22 mg/m3) Key reference: Pozzani, U.C., C.P. Carpenter, P.E. Palm, C.S. Weil, and J.H. Nair. 1959. An investigation of the mammalian toxicity of acetonitrile. J. Occup. Med. 1:634-642. Test species/Strain/Number: Humans, 3 adult males Exposure route/Concentrations/Durations: Inhalation; 40, 80, 160 ppm for 4 h Effects: 40 ppm: slight chest tightness and cooling sensation in lungs (1/3); 80 ppm: no effects (0/2); 160 ppm: slight transitory flushing of the face 2 h after exposure and slight bronchial tightness 5 h later, which resolved overnight (1/2). End point/Concentration/Rationale: Slight chest tightness and cooling sensation at 40 ppm. Uncertainty factors/Rationale: Interspecies: 1 Intraspecies: 1, mild effect is considered to have occurred in a sensitive subject because no symptoms were reported by two other subjects exposed to the same regimen and no effects were report in subjects exposed at 80 ppm for 4 h. Modifying factor: 3, because of sparse database for AEGL-1 effects. Animal-to-human dosimetric adjustment: Not applicable Time scaling: Concentration held constant across the 10-min to 4-h durations. No human data on exposures of durations less than 4 h are available; thus, time scaling to shorter durations could yield values eliciting symptoms above those defined by AEGL-1. An 8-h AEGL-1 value was not recommended because 13 ppm is essentially the same as the 8-h AEGL-2 value of 14 ppm. Data adequacy: Human data were used to derive the AEGL-1 values. Values are considered protective because no effect occurred in other subjects exposed at higher concentrations. a Not recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects. AEGL-2 Values for Acetonitrile 10 min 30 min 1h 4h 8h 80 ppm 80 ppm 50 ppm 21 ppm 14 ppm (130 mg/m3) (130 mg/m3) (84 mg/m3) (35 mg/m3) (24 mg/m3) Data adequacy: In the absence of specific data on acetonitrile to determine AEGL-2 values, estimates were made by dividing the AEGL-3 values by 3. 

104 Acute Exposure Guideline Levels AEGL-3 Values for Acetonitrile 10 min 30 min 1h 4h 8h 240 ppm 240 ppm 150 ppm 64 ppm 42 ppm (400 mg/m3) (400 mg/m3) (250 mg/m3) (110 mg/m3) (71 mg/m3) Key reference: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Test species/Strain/Sex/Number: Rats, Sprague-Dawley, pregnant females, 20 per group Exposure route/Concentrations/Duration: Inhalation; 900, 1,200, 1,500, or 1,800 ppm for 6 h/d on gestational days 6-20 End point/Concentration/Rationale: No-effect level for maternal and fetal lethality (1,500 ppm for 6 h) Effects: Implants per litter Sites per litter Concentration Maternal mortality (mean ± SD) (mean ± SD) 0 ppm 0/20 4.40 ± 6.26 4.40 ± 6.26 900 ppm 0/20 4.61 ± 5.30 4.28 ± 4.92 1,200 ppm 0/20 3.68 ± 5.95 3.68 ± 5.96 1,500 ppm 0/20 4.40 ± 4.77 4.03 ± 4.82 1,800 ppm 8/20 21.78 ± 38.68a 21.78 ± 36.68a a Significantly different from control, p < 0.01. Uncertainty factors/Rationale: Interspecies: 10, default value was applied because no comparable data were identified for similar exposures (repeated inhalation exposure during gestation) in other species. Intraspecies: 3, because human accidental and occupational exposures indicate that there are individual differences in sensitivity to hydrogen cyanide (the metabolically-liberated toxicant), but potential differences in susceptibility among humans are not expected to greater than three-fold (NRC 2002). Furthermore, application of a default uncertainty factor of 10 would result in AEGL-3 values that would be inconsistent with the database (220 ppm for 1 h, 93 ppm for 4 h, and 60 ppm for 8 h are values in the range of concentrations (40-160 ppm) causing only minor effects in humans [Pozzani et al. 1959]). Modifying factor: Not applicable Animal-to-human dosimetric adjustment: Insufficient data Time scaling: Cn × t = k, where n = 1.6 (derived from rat lethality data for exposure durations ranging from 15 min to 8 h). Time scaling was not performed for the 10-min AEGL value because of the uncertainty associated with extrapolating a point-of-departure based on a 6-h exposure to a 10-min value. The 10-min AEGL-3 value was set equal to the 30-min AEGL value. Data adequacy: Well-conducted study with appropriate end point for AEGL-3 values. 

Aliphatic Nitriles 105 Derivation Summary for Isobutyronitrile AEGL-1 Values for Isobutyronitrile The data on isobutyronitrile were insufficient for deriving AEGL-1 values, so no values are recommended. AEGL-2 Values for Isobutyronitrile 10 min 30 min 1h 4h 8h 2.5 ppm 2.5 ppm 2.0 ppm 1.3 ppm 0.83 ppm (7.1 mg/m3) (7.1 mg/m3) (5.7 mg/m3) (3.7 mg/m3) (2.3 mg/m3) Data adequacy: In the absence of specific data on isobutyronitrile to determine AEGL-2 values, estimates were made by dividing the AEGL-3 values by 3. AEGL-3 Values for Isobutyronitrile 10 min 30 min 1h 4h 8h 7.6 ppm 7.6 ppm 6.1 ppm 3.8 ppm 2.5 ppm (22 mg/m3) (22 mg/m3) (17 mg/m3) (11 mg/m3) (7.1 mg/m3) Key reference: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Test species/Strain/Sex/Number: Rats, Sprague-Dawley, pregnant females, 21 per group Exposure route/Concentrations/Durations: 50, 100, 200, or 300 ppm for 6 h on gestational days 6-20 End point/Concentration/Rationale: No maternal death at 100 ppm for 6 h Effects: Concentration Maternal mortality 50 ppm 0/21 100 ppm 0/21 200 ppm 1/21 300 ppm 3/21 A statistically significant increase in fetal resorptions was observed in dams exposed at 300 ppm. Uncertainty factors/Rationale: Interspecies: 10, default value was applied because no comparable data were identified for similar exposures (repeated inhalation exposure during gestation) in other species. Intraspecies: 3, because human accidental and occupational exposures indicate that there are individual differences in sensitivity to hydrogen cyanide (the metabolically-liberated toxicant), but potential differences in susceptibility among humans are not expected to greater than three-fold (NRC 2002). Modifying factor: None Animal-to-human dosimetric adjustment: Insufficient data (Continued) 

106 Acute Exposure Guideline Levels AEGL-3 Values for Isobutyronitrile Continued Time scaling: Cn × t = k, where default values of n = 3 for extrapolation to the 10- and 30-min durations and n = 1 for extrapolation to the 4- and 8-h durations were used to calculate AEGL values that are protective of human health (NRC 2001). The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with extrapolating a point-of-departure based on a 6-h exposure to a 10-min value. Data adequacy: Database is sparse. Derivation Summary for Propionitrile AEGL-1 Values for Propionitrile The data on propionitrile were insufficient for deriving AEGL-1 values, so no values are recommended. AEGL-2 Values for Propionitrile 10 min 30 min 1h 4h 8h 3.7 ppm 3.7 ppm 3.0 ppm 1.9 ppm 1.3 ppm (8.3 mg/m3) (8.3 mg/m3) (6.8 mg/m3) (4.3 mg/m3) (2.9 mg/m3) Data adequacy: In the absence of specific data on propionitrile to determine AEGL-2 values, estimates were made by dividing the AEGL-3 values by 3. AEGL-3 Values for Propionitrile 10 minute 30 minute 1 hour 4 hour 8 hour 11 ppm 11 ppm 9.1 ppm 5.7 ppm 3.8 ppm (25 mg/m3) (25 mg/m3) (20 mg/m3) (13 mg/m3) (8.6 mg/m3) Key reference: Saillenfait, A.M., P. Bonnet, J.P. Gurnier, and J. de Ceaurriz, J. 1993. Relative developmental toxicities of inhaled aliphatic mononitriles in rats. Fundam. Appl. Toxicol. 20(3):365-375. Test species/Strain/Sex/Number: Rats, Sprague-Dawley, pregnant females, 22-23 per group Exposure route/Concentrations/Durations: Inhalation, 50, 100, 150, or 200 ppm for 6 h on gestational days 6-20 End point/Concentration/Rationale: No maternal death or increase in fetal resorptions (150 ppm for 6 h) Effects: Concentration Maternal mortality 50 ppm 0/22 100 ppm 0/23 150 ppm 0/22 200 ppm 2/23 A statistically significant increase in fetal resorptions was observed in dams exposed at 200 ppm. 

Aliphatic Nitriles 107 Uncertainty factors/Rationale: Interspecies: 10, default value was applied because no comparable data were identified for similar exposures (repeated inhalation exposure during gestation) in other species. Intraspecies: 3, because human accidental and occupational exposures indicate that there are individual differences in sensitivity to hydrogen cyanide (the metabolically-liberated toxicant), but potential differences in susceptibility among humans are not expected to greater than three-fold (NRC 2002). Modifying factor: None Animal-to-human dosimetric adjustment: Insufficient data Time scaling: Cn × t = k, where default values of n = 3 for extrapolation to the 10- and 30-min durations and n = 1 for extrapolation to the 4- and 8-h durations were used to calculate AEGL values that are protective of human health (NRC 2001). The 10-min AEGL-3 value was set equal to the 30-min AEGL-3 value because of the uncertainty associated with extrapolating a point-of-departure based on a 6-h exposure to a 10-min value. Data adequacy: Database is sparse. Derivation Summary for Chloroacetonitrile AEGL-1 Values for Chloroacetonitrile The data on chloroacetonitrile were insufficient for deriving AEGL-1 values, so no values are recommended. AEGL-2 Values for Chloroacetonitrile 10 min 30 min 1h 4h 8h 8.0 ppm 8.0 ppm 5.0 ppm 2.1 ppm 1.4 ppm (25 mg/m3) (25 mg/m3) (15 mg/m3) (6.5 mg/m3) (4.3 mg/m3) Data adequacy: No chemical-specific data were available to derive AEGL-2 values for chloroacetonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloroacetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-2 values were divided by 10 to approximate AEGL-2 values for chloroacetonitrile. AEGL-3 Values for Chloroacetonitrile 10 min 30 min 1h 4h 8h 24 ppm 24 ppm 15 ppm 6.4 ppm 4.2 ppm (74 mg/m3) (74 mg/m3) (46 mg/m3) (20 mg/m3) (13 mg/m3) Data adequacy: No chemical-specific data were available to derive AEGL-3 values for chloroacetonitrile. Mouse intraperitoneal LD50 data suggest that, on a molar basis, chloroacetonitrile is approximately 10 times more toxic than acetonitrile (see Table 1-1). Therefore, the acetonitrile AEGL-3 values were divided by 10 to approximate AEGL-3 values for chloroacetonitrile. 

108 Acute Exposure Guideline Levels Derivation Summary for Malononitrile AEGL-1 Values for Malononitrile The data on malononitrile are insufficient for deriving AEGL-1 values, so no values are recommended. AEGL-2 Values for Malononitrile 10 min 30 min 1h 4h 8h 1.2 ppm 1.2 ppm 0.77 ppm 0.32 ppm 0.22 ppm (3.3 mg/m3) (3.3 mg/m3) (2.1 mg/m3) (0.87 mg/m3) (0.59 mg/m3) Data adequacy: No chemical-specific data are available to derive AEGL-2 values for malononitrile. Intraperitoneal LD50 data from studies of mice suggest that, on a molar basis, malononitrile is approximately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the AEGL-2 values for acetonitrile were divided by 65 to approximate AEGL-2 values for malononitrile. AEGL-3 Values for Malononitrile 10 min 30 min 1h 4h 8h 3.7 ppm 3.7 ppm 2.3 ppm 0.98 ppm 0.65 ppm (10 mg/m3) (10 mg/m3) (6.2 mg/m3) (2.7 mg/m3) (1.7 mg/m3) Data adequacy: No chemical-specific data are available to derive AEGL-3 values for malononitrile. Intraperitoneal LD50 data from studies of mice suggest that, on a molar basis, malononitrile is approximately 65 times more toxic than acetonitrile (see Table 1-1). Therefore, the AEGL-3 values for acetonitrile were divided by 65 to approximate AEGL-3 values for malononitrile. 

Aliphattic Nitriles 1109 AP PPENDIX D CATEGORY PLOTS P FOR SELECTED S A ALIPHATIC N NITRILES FIGUR RE D-1 Category y plot of toxicity y data and AEGL L values for acetoonitrile. FIGUR RE D-2 Category y plot of toxicity y data and AEGL L values for isobutyronitrile. 

110 TABLE D-1 Data Used in Category Plot for Acetonitrile Source Species Sex No. Exposures ppm Minutes Category Comments AEGL-1 13 10 AEGL AEGL-1 13 30 AEGL AEGL-1 13 60 AEGL AEGL-1 13 240 AEGL AEGL-1 NR 480 AEGL AEGL-2 80 10 AEGL AEGL-2 80 30 AEGL AEGL-2 50 60 AEGL AEGL-2 21 240 AEGL AEGL-2 14 480 AEGL AEGL-3 240 10 AEGL AEGL-3 240 30 AEGL AEGL-3 150 60 AEGL AEGL-3 64 240 AEGL AEGL-3 42 480 AEGL Pozzani et al. 1959 Dog Male 1 2,000 240 2 Pulmonary congestion or hemorrhage Pozzani et al. 1959 Dog Male 1 16,000 240 3 100% mortality (3/3) Pozzani et al. 1959 Guinea pig 1 4,000 240 2 Pulmonary congestion or hemorrhage Pozzani et al. 1959 Guinea pig 1 5,655 240 SL LC50 Pozzani et al. 1959 Guinea pig 1 8,000 240 3 100% mortality (6/6) Willhite 1983 Hamster Female 1 1,800 60 0 No maternal death Willhite 1983 Hamster Female 1 3,800 60 SL Mortality (1/6); no signs of toxicity in others 

Willhite 1983 Hamster Female 1 3,800 60 0 No embryo lethality Pozzani et al. 1959 Human Male 1 40 240 1 n = 3, no subjective symptoms, slight chest tightness followed by a cooling sensation in lungs Pozzani et al. 1959 Human Male 1 80 240 0 n = 2, no subjective symptoms Pozzani et al. 1959 Human Male 1 160 240 1 n = 2, slight transitory flushing of the face, slight bronchial tightness MPI 1998 Mouse Both 1 3,039 240 SL 20% mortality (2/10) Willhite 1981 Mouse 1 2,693 60 SL LC50 Willhite 1981 Mouse 1 5,000 60 3 100% mortality (10/10) Pozzani et al. 1959 Rabbit 1 2,000 240 2 Pulmonary congestion or hemorrhage Pozzani et al. 1959 Rabbit 1 2,828 240 SL LC50 Pozzani et al. 1959 Rabbit 1 4,000 240 3 100% mortality (4/4) DuPont 1968 Rat Male 1 17,100 240 SL LC50 Haguenoer et al. 1975 Rat 1 25,000 30 3 100% mortality (3/3) Monsanto 1986 Rat 1 10,100 240 2 Hemorrhagic lungs Monsanto 1986 Rat 1 13,600 240 SL Mortality (1/10), hemorrhagic lungs, corneal opacity Northview Pacific Rat Both 1 4,760 60 0 1/5 females lost weight, no mortality or Labs 1989 gross abnormalities Mast et al. 1994 Rat Female 14 1,200 360 0 No embryo lethality Mast et al. 1994 Rat Female 13 1,200 360 SL 6% (2/33) in dams NTP 1996 Rat Male 65 400 360 0 No death NTP 1996 Rat Female 65 800 360 0 No death NTP 1996 Rat Male 65 800 360 SL 10% mortality (1/10) (Continued) 111 

112 TABLE D-1 Continued Source Species Sex No. Exposures ppm Minutes Category Comments Pozzani et al. 1959 Rat Both 1 1,000 480 2 Pulmonary congestion or hemorrhage Pozzani et al. 1959 Rat Both 1 2,000 480 SL Mortality (1/24), pulmonary congestion or hemorrhage Pozzani et al. 1959 Rat Both 1 4,000 240 2 Pulmonary congestion or hemorrhage Pozzani et al. 1959 Rat Both 1 4,000 480 SL Mortality (2/24), pulmonary congestion or hemorrhage Pozzani et al. 1959 Rat Male 1 7,551 480 SL LC50 Pozzani et al. 1959 Rat Both 1 8,000 240 SL Mortality (7/12) Pozzani et al. 1959 Rat Female 1 12,435 480 SL LC50 Pozzani et al. 1959 Rat Both 1 32,000 240 3 100% mortality (24/24) Pozzani et al. 1959 Rat Female 1 32,000 480 3 100% mortality (24/24) Pozzani et al. 1959 Rat 1 53,000 15 2 No death Pozzani et al. 1959 Rat 1 53,000 30 SL 50% mortality (3/6) Saillenfait et al. 1993 Rat Female 14 1,500 360 0 No maternal death or embryo lethality Saillenfait et al. 1993 Rat Female 14 1,800 360 3 40% (8/20) mortality in dams, embryo lethality UCC 1965 Rat 1 4,000 240 SL 10% mortality (3/30) For category: 0 = no effect, 1 = discomfort, 2 = disabling, SL = some lethality, 3 = lethal 

TABLE D-2 Data Used in Category Plot for Isobutyronitrile Source Species Sex No. Exposures ppm Minutes Category Comments AEGL-1 NR 10 AEGL AEGL-1 NR 30 AEGL AEGL-1 NR 60 AEGL AEGL-1 NR 240 AEGL AEGL-1 NR 480 AEGL AEGL-2 2.5 10 AEGL AEGL-2 2.5 30 AEGL AEGL-2 2.0 60 AEGL AEGL-2 1.3 240 AEGL AEGL-2 0.83 480 AEGL AEGL-3 7.6 10 AEGL AEGL-3 7.6 30 AEGL AEGL-3 6.1 60 AEGL AEGL-3 3.8 240 AEGL AEGL-3 2.5 480 AEGL Katz 1986 Rat Male 1 1,248 60 SL Mortality (1/5) Katz 1986 Rat Male 1 2,709 60 3 Mortality (5/5) Katz 1986 Rat Female 1 1,248 60 0 No clinical signs Katz 1986 Rat Female 1 1,778 60 SL Mortality (1/5) (Continued) 113 

114 TABLE D-2 Continued Source Species Sex No. Exposures ppm Minutes Category Comments Eastman Kodak 1986a Rat Male 1 1,200 60 2 “Appreciable” differences noted in expiratory reserve volume, residual volume, dynamic compliance (up to 76% decrease), and FEV 10% Eastman Kodak 1986a Rat Male 1 1,800 60 SL Mortality (2/4) Eastman Kodak 1986a Rat Male 1 2,700 60 3 Mortality (4/4) Eastman Kodak1986b Rat Male 1 1,233 60 SL Mortality (1/5) Smyth et al. 1962 Rat 1 500 240 2 No mortality, no details provided Tsurumi and Rat 1 37,000 4 0 Mortality (0/10), no other effects described Kawada 1971 Tsurumi and Rat 1 37,000 5 SL Mortality (1/10), no other effects described Kawada 1971 Tsurumi and Rat 1 37,000 10 3 Mortality (10/10), no other effects described Kawada 1971 Tsurumi and Mouse 1 37,000 0.25 2 Mortality (0/10), no other effects described Kawada 1971 Tsurumi and Mouse 1 37,000 0.5 SL Mortality (3/10), no other effects described Kawada 1971 Tsurumi and Mouse 1 37,000 2 3 Mortality (10/10), no other effects described Kawada 1971 AIHA 1992 Human 1 25 3 0 An exposure of a few minutes to estimated concentrations of 20-25 ppm from a isobutyronitrile spill did not produce symptoms of cyanide poisoning 

Saillenfait et al. 1993 Rat Female 15 50 360 1 Gestation days 6-20 Saillenfait et al. 1993 Rat Female 15 100 360 1 Gestation days 6-20 Saillenfait et al. 1993 Rat Female 15 200 360 SL Gestation days 6-20, mortality (1/21), decrease in fetal weight Saillenfait et al. 1993 Rat Female 15 300 360 SL Gestation days 6-20, mortality (3/21), increased embryonic resorptions, decreased fetal weight, unilateral hydronephrosis For category: 0 = no effect, 1 = discomfort, 2 = disabling, SL = some lethality, 3 = lethal 115 

116 Accute Exposure Guideline Levels FIGUR RE D-3 Category y plot of toxicity y data and AEGL L values for proppionitrile. FIGUR RE D-4 Category y plot of AEGL values v for chlorooacetonitrile. 

TABLE D-3 Data Used in Category Plot for Propionitrile Source Species Sex No. Exposures ppm Minutes Category Comments AEGL-1 NR 10 AEGL AEGL-1 NR 30 AEGL AEGL-1 NR 60 AEGL AEGL-1 NR 240 AEGL AEGL-1 NR 480 AEGL AEGL-2 3.7 10 AEGL AEGL-2 3.7 30 AEGL AEGL-2 3.0 60 AEGL AEGL-2 1.9 240 AEGL AEGL-2 1.3 480 AEGL AEGL-3 11 10 AEGL AEGL-3 11 30 AEGL AEGL-3 9.1 60 AEGL AEGL-3 5.7 240 AEGL AEGL-3 3.8 480 AEGL Saillenfait et al. 1993 Rat Female 14 150 360 0 No maternal or fetal death Saillenfait et al. 1993 Rat Female 14 200 360 SL Maternal death (2/23) and increased embryo lethality (increased mean % non-surviving implants/litter, increased mean % resorption sites/litter) (Continued) 117 

118 TABLE D-3 Continued Source Species Sex No. Exposures ppm Minutes Category Comments Younger Labs 1978 Rat Both 1 690 240 2 Salivation, lethargy, weakness, tremors, convulsions Younger Labs 1978 Rat Male 1 1,100 240 SL Mortality (5/10), salivation, lethargy, weakness, tremors, convulsions, collapse and death Younger Labs 1978 Rat Male 1 1,700 240 SL Mortality (5/10), salivation, lethargy, weakness, tremors, convulsions, collapse, death Younger Labs 1978 Rat Male 1 2,800 240 SL Mortality (8/10), salivation, lethargy, weakness, tremors, convulsions, collapse, death Younger Labs 1978 Rat Both 1 4,400 240 3 Mortality (10/10), salivation, lethargy, weakness, tremors, convulsions, collapse, death Younger Labs 1978 Rat Both 1 6,900 240 3 Mortality (10/10), salivation, lethargy, weakness, tremors, convulsions, collapse, death Younger Labs 1979 Rat Male 1 39,432 75 3 Mortality (6/6) Lewis 1996 Mouse 1 34 SL Intraperitoneal LD50 Tanii and Mouse Male 1 36 SL Oral LD50 Hashimoto 1984 Willhite and Smith Mouse Male 1 163 60 SL LC50 1981 Scolnick et al. 1993 Human Male 1 33.8 120 2 Headache, nausea, dizziness Scolnick et al. 1993 Human Male 1 33.8 420 2 Coma, seizures, bilateral interstitial infiltrates (lungs), lethargy, headaches, dizziness For category: 0 = no effect, 1 = discomfort, 2 = disabling, SL = some lethality, 3 = lethal 

Aliphattic Nitriles 1119 TABLE E D-4 Data Ussed in Category y Plot for Chlooroacetonitrile No. Source Species Sex Exposures ppm M Minutes Categgory Commentts AEGL-1 NR 100 AEGL L AEGL-1 NR 300 AEGL L AEGL-1 NR 600 AEGL L AEGL-1 NR 2440 AEGL L AEGL-1 NR 4880 AEGL L AEGL-2 8.0 100 AEGL L AEGL-2 8.0 300 AEGL L AEGL-2 5.0 600 AEGL L AEGL-2 2.1 2440 AEGL L AEGL-2 1.4 4880 AEGL L AEGL-3 24 100 AEGL L AEGL-3 24 300 AEGL L AEGL-3 15 600 AEGL L AEGL-3 6.4 2440 AEGL L AEGL-3 4.2 4880 AEGL L For cateegory: 0 = no efffect, 1 = discomffort, 2 = disablinng, SL = some leethality, 3 = lethal FIGUR RE D-5 Category y plot of AEGL values v for malonnonitrile. 

120 Acute Exposure Guideline Levels TABLE D-5 Data Used in Category Plot for Malononitrile No. Source Species Sex Exposures ppm Minutes Category Comments AEGL-1 NR 10 AEGL AEGL-1 NR 30 AEGL AEGL-1 NR 60 AEGL AEGL-1 NR 240 AEGL AEGL-1 NR 480 AEGL AEGL-2 1.2 10 AEGL AEGL-2 1.2 30 AEGL AEGL-2 0.77 60 AEGL AEGL-2 0.32 240 AEGL AEGL-2 0.22 480 AEGL AEGL-3 3.7 10 AEGL AEGL-3 3.7 30 AEGL AEGL-3 2.3 60 AEGL AEGL-3 0.98 240 AEGL AEGL-3 0.65 480 AEGL For category: 0 = no effect, 1 = discomfort, 2 = disabling, SL = some lethality, 3 = lethal.