3

Selected Chlorosilanes1

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 Guideline Levels for Hazardous Substances (NAC/AEGL Committee) has been established 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 distinguished 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 effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.

1This document was prepared by the AEGL Development Team composed of Chery Bast (Oak Ridge National Laboratory), Julie M. Klotzbach (Syracuse Research Corporation), and Chemical Manager Ernest V. Falke (National Advisory Committee [NAC] on Acute Exposure Guideline Levels for Hazardous Substances). The NAC reviewed and revised the document and AEGLs as deemed necessary. Both the document and the AEGL values were then reviewed by the National Research Council (NRC) Committee on Acute Exposure Guideline Levels. The NRC committee 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).



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3 Selected Chlorosilanes1 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 effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure. 1 This document was prepared by the AEGL Development Team composed of Chery Bast (Oak Ridge National Laboratory), Julie M. Klotzbach (Syracuse Research Corpora- tion), and Chemical Manager Ernest V. Falke (National Advisory Committee [NAC] on Acute Exposure Guideline Levels for Hazardous Substances). The NAC reviewed and revised the document and AEGLs as deemed necessary. Both the document and the AEGL values were then reviewed by the National Research Council (NRC) Committee on Acute Exposure Guideline Levels. The NRC committee 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). 106

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107 Selected Chlorosilanes 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 levels for the general public, including susceptible subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the correspond- ing AEGL. SUMMARY Chlorosilanes contain one or more chlorine atoms covalently bonded to a silicon atom; the maximum chlorine-to-silicon ratio is four. Chlorosilanes are chemical intermediates used in the production of silicone and silicone- containing materials, and are often produced in bulk and transported to manufac- turing sites for use. Chlorosilanes are corrosive, and inhalation exposure might cause nasal, throat, or lung irritation, coughing, wheezing, and shortness of breath. Chlorosilanes react rapidly with water, steam, or moisture; hydrolysis yields hydrogen chloride (HCl) gas along with silanols and other condensation products. The 26 chlorosilanes considered in this chapter are: Allyl trichlorosilane Methyl dichlorosilane Amyl trichlorosilane Methyl trichlorosilane Butyl trichlorosilane Methylvinyl dichlorosilane Chloromethyl trichlorosilane Nonyl trichlorosilane Dichlorosilane Octadecyl trichlorosilane Diethyl dichlorosilane Octyl trichlorosilane Dimethyl chlorosilane Propyl trichlorosilane Dimethyl dichlorosilane Tetrachlorosilane Diphenyl dichlorosilane Trichloro(dichlorophenyl)silane Dodecyl trichlorosilane Trichlorophenylsilane Ethyl trichlorosilane Trichlorosilane Hexyl trichlorosilane Trimethyl chlorosilane Methyl chlorosilane Vinyl trichlorosilane 107

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108 Acute Exposure Guideline Levels Although chemical-specific toxicity data are not available for many of these chlorosilanes, acute inhalation data from rat studies are available for struc- turally-similar chlorosilanes (propyl trichlorosilane, methyl trichlorosilane, vinyl trichlorosilane, ethyl trichlorosilane, methylvinyl dichlorosilane, methyl dichlo- rosilane, dimethyl dichlorosilane, dimethyl chlorosilane, trimethylchlorosilane, and tetrachlorosilane). These data suggest that the acute toxicity of chlorosilanes is largely explained by the HCl hydrolysis product; acute toxicity of these chlo- rosilanes is qualitatively (based on clinical signs) and quantitatively (based on molar equivalents of HCl) similar to that of HCl (Jean et al. 2006). On the basis of these data, and in the absence of appropriate chemical- specific data for the chlorosilanes considered in this document, the AEGLs for HCl were used to derive AEGLs for the chlorosilanes. For each class of chloro- silanes (mono-, di-, tri-, and tetra-chlorosilanes), the molar ratio (moles of HCl released per mole of chlorosilane, assuming complete hydrolysis) was used to adjust the AEGL values for HCl to the equivalent concentration of chlorosilane. Detailed information on the derivation of AEGLs for HCl is available in NRC (2004). The calculated values are listed in the Table 3-1. 1. INTRODUCTION Chlorosilanes contain one or more chlorine atoms covalently bonded to a silicon atom; the maximum chlorine-to-silicon ratio is four. Chlorosilanes are chemical intermediates used in the production of silicone and silicone- containing materials, and are often produced in bulk and transported to manufac- turing sites for use. Chlorosilanes react very rapidly with water, steam, or moisture, releasing HCl gas (AIHA 1998, 1999, 2001a,b,c, 2006). The primary vapor detected in air when chlorosilanes are released is HCl; much less of the parent chlorosilane is detectable (Nakashima et al. 1996; Jean et al. 2006). In an experiment using 11 different chlorosilanes, Jean et al. (2006) reported that the percentage of parent chlorosilane in the test atmosphere ranged from <10% to 58%; other constitu- ents of the atmosphere (in addition to HCl) included silanols and other conden- sation products. When x-ray microanalysis was performed on air filtered from a dichlorosilane exposure chamber, small (<1 µM in diameter), unidentified parti- cles containing silicon and chloride were detected (Nakashima et al. 1996). Numerous reports of chlorosilane spills and releases have been received by the U.S. Coast Guard National Response Center. For example, between Janu- ary 1990 and July 2007, there were 23 reports of dichlorosilane releases ranging from 6 to 2,596 pounds; 32 reports of trichlorosilane releases ranging from 2.6 to 343 pounds; and 14 reports of tetrachlorosilane releases ranging from 2 to 330 pounds (USCG 2007). Releases were from both fixed and mobile sources and were the result of equipment failure and operator error.

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TABLE 3-1 Summary of AEGL Values for Selected Chlorosilanesa Compound Classification 10 min 30 min 1h 4h 8h End Point (Reference) MONOCHLOROSILANES Dimethyl chlorosilane AEGL-1 1.8 ppm 1.8 ppm 1.8 ppm 1.8 ppm 1.8 ppm AEGLs for HCl AEGL-2 100 ppm 43 ppm 22 ppm 11 ppm 11 ppm (NRC 2004) Methyl chlorosilane AEGL-3 620 ppm 210 ppm 100 ppm 26 ppm 26 ppm Trimethylchlorosilane DICHLOROSILANES Dichlorosilane AEGL-1 0.90 ppm 0.90 ppm 0.90 ppm 0.90 ppm 0.90 ppm AEGLs for HCl AEGL-2 50 ppm 22 ppm 11 ppm 5.5 ppm 5.5 ppm divided by a molar Diethyl dichlorosilane AEGL-3 310 ppm 110 ppm 50 ppm 13 ppm 13 ppm adjustment factor of 2 Dimethyl dichlorosilane (NRC 2004) Diphenyl dichlorosilane Methyl dichlorosilane Methylvinyl dichlorosilane TRICHLOROSILANES Allyl trichlorosilane AEGL-1 0.60 ppm 0.60 ppm 0.60 ppm 0.60 ppm 0.60 ppm AEGL values for HCl AEGL-2 33 ppm 14 ppm 7.3 ppm 3.7 ppm 3.7 ppm divided by a molar Amyl trichlorosilane AEGL-3 210 ppm 70 ppm 33 ppm 8.7 ppm 8.7 ppm adjustment factor of 3 Butyl trichlorosilane (NRC 2004) Chloromethyl trichlorosilane Dodecyl trichlorosilane Ethyl trichlorosilane Hexyl trichlorosilane Methyl trichlorosilane Nonyl trichlorosilane Octadecyl trichlorosilane Octyl trichlorosilane Propyl trichlorosilane 109 (Continued)

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110 TABLE 3-1 Continued Compound Classification 10 min 30 min 1h 4h 8h End Point (Reference) TRICHLOROSILANES (continued) Trichloro(dichlorophenyl)silane Trichlorophenylsilane Trichlorosilane Vinyl trichlorosilane TETRACHLOROSILANE AEGL-1 0.45 ppm 0.45 ppm 0.45 ppm 0.45 ppm 0.45 ppm AEGL values for HCl AEGL-2 25 ppm 11 ppm 5.5 ppm 2.8 ppm 2.8 ppm divided by a molar AEGL-3 160 ppm 53 ppm 25 ppm 6.5 ppm 6.5 ppm adjustment factor of 4 (NRC 2004) a Values given in ppm. To convert ppm to mg/m3: (ppm × molecular weight) ÷ 24.5. See Appendix A for the appropriate molecular weight. For mono-, di-, and tri-chlorosilanes not listed, use of HCl equivalents may be considered for AEGL-value derivation.

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111 Selected Chlorosilanes The chlorosilanes have pungent irritating odors, are corrosive, and inhala- tion exposure might cause nasal, throat, or lung irritation, coughing, wheezing, and shortness of breath. Although chemical-specific toxicity data are not avail- able for many of the chlorosilanes, acute inhalation data from rat studies are available for structurally-similar chlorosilanes (propyl trichlorosilane, methyl trichlorosilane, vinyl trichlorosilane, ethyl trichlorosilane, methylvinyl dichloro- silane, methyl dichlorosilane, dimethyl dichlorosilane, dimethyl chlorosilane, trimethylchlorosilane, and tetrachlorosilane). These data suggest that the acute toxicity of chlorosilanes is from the HCl hydrolysis product; acute toxicity of the chlorosilanes is qualitatively (based on clinical signs) and quantitatively (based on molar equivalents of HCl) similar to that of HCl (Jean et al. 2006) (see Sec- tion 4.3). On the basis, and in the absence of adequate chemical-specific data for the chlorosilanes considered in this document, the AEGL values for HCl (NRC 2004) were used to obtain AEGL values for the chlorosilanes. The molar ratio (moles HCl released per mole of chlorosilane, assuming complete hydrolysis) was used to adjust the AEGL values for HCl to the equivalent concentration of chlorosilane. Available physicochemical data for the 26 chlorosilanes covered in this chapter are presented in Appendix A. 2. HUMAN TOXICITY DATA An accidental release of tetrachlorosilane at a chemical plant in a south San Francisco industrial park provided some human exposure data (Kizer et al. 1984). A delivery truck taking a short-cut through a chemical plant hit the tank- coupling unit of a tetrachlorosilane storage tank. The pipeline ruptured and the tetrachlorosilane liquid spilled onto the moist ground; it hydrolyzed rapidly and formed a large gray-white cloud that quickly spread. Workers were unable to stop the leak because the valve was behind a wire enclosure, and approximately 1,200 gallons of tetrachlorosilane was released before the leak was stopped sev- eral hours later. By that time, the cloud had risen 500 feet and had spread more than a mile over the industrial park. Five- to ten-thousand employees from 600 businesses over 3 square miles were evacuated. Twenty-eight people reported to local hospitals for treatment of eye or airway irritation. Seven of the patients were employees at the chemical plant, and six of them were smokers. The re- maining 21 patients were firemen, policemen, passersby, and employees of other companies in the area. There were no deaths, and no one was hospitalized. Six of the chemical plant employees were referred for further evaluation; these em- ployees were all male, ranged in age from 25 to 56, and were all smokers. Their exposures ranged from 10 to 20 min in duration. Symptoms generally resolved within 24 h, and included lacrimation, rhinorrhea, burning of the mouth and throat, headache, coughing, and wheezing. Pulmonary function tests were nor- mal except that mild obstructive airway disease was noted in four patients. However, it was unclear if the disease was from exposure to tetrachlorosilane or

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112 Acute Exposure Guideline Levels related to smoking status. Two patients also complained of pedal dysesthesias after the accident. No air concentrations of tetrachlorosilane or HCl were re- ported. Reactive airways dysfunction syndrome is an asthma-like condition that develops after a single exposure to high concentrations of a chemical irritant, and has been described after exposure to HCl. Symptoms occur within minutes to hours after the initial exposure and can persist as nonspecific bronchial hyper- responsiveness for months to years (Bernstein 1993). Promisloff et al. (1990) reported reactive airways dysfunction syndrome in three male police officers (36-45 years of age) who responded to a roadside chemical spill. The subjects were exposed to unquantified amounts of sodium hydroxide, tetrachlorosilane, and HCl as a byproduct of trichlorosilane hydrolysis. Because of the mixture of irritants involved in the release, it is probable that all of the compounds contrib- uted to the syndrome observed after this accident. 3. ANIMAL TOXICITY DATA 3.1. Acute Toxicity One-hour LC50 (lethal concentration, 50% lethality) studies were con- ducted for 10 chlorosilanes: tetrachlorosilane, propyl trichlorosilane, vinyl tri- chlorosilane, methyl trichlorosilane, ethyl trichlorosilane, methylvinyl dichloro- silane, dimethyl dichlorosilane, methyl dichlorosilane, trimethyl chlorosilane, and dimethyl chlorosilane (Jean et al. 2006). In each study, groups of five male and five female Fischer 344 rats were exposed to varying concentrations of a chlorosilane for 1 h and observed for up to 14 days. The studies appeared to conform to Good Laboratory Practices and were well-described. The authors used nominal concentrations to calculate LC50 values because chlorosilanes react rapidly with moisture to produce HCl and other hydrolysis products. Using ac- tual chamber concentrations of chlorosilanes would only reflect toxicity of the parent compound, not the toxicity of the parent compound and hydrolysis prod- ucts. There was agreement between the electrolytic conductivity detector and the nominal concentrations, indicating efficient vaporization of the test material. Clinical signs were consistent with HCl exposure and included lacrima- tion, salivation, dried material around the eyes or nose, green staining around the nose and mouth, and perineal urine staining. Labored breathing, rales, hypoac- tivity, closed or partially closed eyes, prostration, corneal opacity or opaqueness, and swollen or necrotic paws also were observed. Hemorrhage, congestion, and consolidation of the lungs; ectasia of the lungs; gaseous distension of the gastro- intestinal tract; absence of body fat; obstruction of nostrils; dried or firm nares; alopecia around the eyes; and discoloration of hair were observed at necropsy. Mortality data and LC50 values from 1-h exposure studies with rats are summa- rized in Table 3-2.

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113 Selected Chlorosilanes TABLE 3-2 Mortality Data and LC50 Values from 1-Hour Exposure Studies with Rats Exposure Mortality LC50, ppm Concentration (95% confidence Compound (ppm) Male Female Total limits) 1,312 (1,006-1,529) a Tetrachlorosilane 1,209 1/5 2/5 3/10 1,497 5/5 3/5 8/10 3,051 5/5 5/5 10/10 1,352 (1,254-1,455) a Propyl trichlorosilane 1,123 0/5 0/5 0/10 1,317 2/5 2/5 4/10 1,414 3/5 4/5 7/10 1,611 (1,505-1,724) b Vinyl trichlorosilane 1,186 0/5 0/5 0/10 1,605 4/5 2/5 6/10 1,681 2/5 1/5 3/10 1,989 5/5 5/5 10/10 1,365 (1,174-2,104) a Methyl trichlorosilane 622 0/5 0/5 0/10 1,047 0/5 1/5 1/10 1,439 4/5 2/5 6/10 3,075 5/5 5/5 10/10 1,257 (1,175-1,320) a Ethyl trichlorosilane 1,156 1/5 1/5 2/10 1,326 4/5 2/5 6/10 1,415 5/5 5/5 10/10 2,021 (1,806-2,257) a Methylvinyl 1,597 1/5 0/5 1/10 dichlorosilane 2,005 3/5 2/5 5/10 2,119 3/5 3/5 6/10 2,242 4/5 3/5 7/10 2,092 (1,492-2,240) a Dimethyl 1,309 0/5 0/5 0/10 dichlorosilane 2,077 4/5 1/5 5/10 2,353 5/5 3/5 8/10 2,762 5/5 5/5 10/10 1,785 (1,671-1,963) a Methyl 1,431 0/5 0/5 0/10 dichlorosilane 1,678 1/5 2/5 3/10 1,889 4/5 3/5 7/10 4,257 (4,039-4,488) b Trimethyl 3,171 0/5 0/5 0/10 chlorosilane 4,139 2/5 0/5 2/10 4,268 3/5 3/5 6/10 5,121 5/5 5/5 10/10 4,478 (4,281-6,327) a Dimethyl 4,108 1/5 1/5 2/10 chlorosilane 4,179 1/5 1/5 2/10 4,409 3/5 3/5 6/10 4,589 3/5 2/5 5/10 a Probit analysis. b Spearman-Karber analysis. Source: Jean et al. 2006. Reprinted with permission; copyright 2006, Inhalation Toxi- cology.

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114 Acute Exposure Guideline Levels In another study, groups of 10 male ICR mice were exposed for 4 h to nominal concentrations of dichlorosilane at 49-259 ppm, followed by a 14-day observation period (Nakashima et al. 1996). Mortality was 0/10, 0/10, 1/10, 6/10, 4/10, 10/10, 10/10, 9/10, and 10/10 for groups exposed at 0, 49, 100, 131, 141, 199, 216, 218, and 259 ppm, respectively. An LC50 of 144 ppm was calculated. 3.2. Developmental and Reproductive Toxicity No data on developmental or reproductive toxicity were found. 3.3. Genotoxicity The only genotoxicity data found were for tetrachlorosilane. Tetrachloro- silane was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA 1535, TA1537, or TA1538; Saccharomyces cerevisiae strain D-4; or Escheris- chia coli strains W3110/polA+ and P3478/polA- either with or without metabolic activation. It was also negative in a L5178Y mouse lymphoma assay (AIHA 1999). 3.4. Chronic Toxicity and Carcinogenicity No data on chronic toxicity or carcinogenicity were found. 3.5. Summary Although toxicity data are sparse for individual chlorosilanes, well- conducted 1-h inhalation toxicity studies in rats are available for a series of chlo- rosilanes (Jean et al. 2006). In general, LC50 values for monochlorosilanes were approximately twice the LC50 values for dichlorosilanes and three times the LC50 values for trichlorosilanes. Tetrachlorosilane had an LC50 value similar to the trichlorosilanes; however, there were experimental difficulties at the lowest con- centration tested. Clinical signs were indicative of severe irritation or corrosion. The evidence suggests that the acute toxicity of chlorosilanes is largely attribut- able to the release of HCl; however, no information on the identity or potential toxicity of other decomposition products was found. No data concerning devel- opmental or reproductive toxicity, genotoxicity, or carcinogenicity for exposure to the chlorosilanes were found in the literature. 4. SPECIAL CONSIDERATIONS 4.1. Metabolism and Disposition No information was found concerning the metabolism and disposition of chlorosilanes.

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115 Selected Chlorosilanes 4.2. Mechanism of Toxicity Chlorosilanes react violently with water to produce HCl gas (AIHA 1998, 1999, 2001a,b,c, 2006). In an experiment using 11 different chlorosilanes, Jean et al. (2006) reported that the percentage of parent chlorosilane in the test at- mosphere range from <10 to 58%; other constituents of the atmosphere (in addi- tion to HCl) included silanols and other condensation products. Nakashima et al. (1996) reported that small particles containing silicon and chlorine were de- tected in an inhalation exposure chamber into which dichlorosilane was intro- duced; the identity and quantity of particles were not reported. IPCS (2002a) reported that, when heated, trimethylchlorosilane decomposition could release HCl and phosgene. No other information on potential decomposition products of chlorosilanes was found. Available data suggest that the acute toxicity of chloro- silanes is largely from the HCl hydrolysis product; acute toxicity of the chlorosi- lanes is qualitatively (based on clinical signs) and quantitatively (based on molar equivalents of HCl) similar to that of HCl. 4.3. Structure Activity Relationships A 1-h LC50 study with HCl was performed in rats and used for comparison with the chlorosilane 1-h LC50 values (Jean et al. 2006). According to the au- thors, the study with HCl was unpublished, but was performed in the same labo- ratory and was conducted using the same protocol as that used in the chlorosi- lane study (1-h whole-body exposure with a 14-day recovery period). Five rats per sex were exposed to HCl at 0, 2,456, 3,236, or 4,210 ppm for 1 h and ob- served for up to 14 days. Chamber concentrations were determined by a Fourier transform infrared spectrophotometer analyzer. Clinical signs included labored breathing; gasping; emaciation; rough coat; lethargy; corneal opacity; crusting, necrotic, discolored, and blocked nares or nasal opening; paws with missing, necrotic, or swollen digits; and weight loss. Gross pathology of animals dying during the study included irritation and necrosis of most extremities, severe res- piratory-tract injuries, and corneal opacity. A 1-h LC50 of 3,627 ppm was calcu- lated for HCl. The LC50 data obtained for the chlorosilanes showed a strong association with chlorine content for the mono-, di-, and tri-chlorosilanes. In general, LC50 values for monochlorosilanes were approximately twice the LC50 values for di- chlorosilanes and three times the LC50 values for trichlorosilanes. Tetrachlorosi- lane exhibited an LC50 value similar to the trichlorosilanes. The predicted 1-h LC50 values for the chlorosilanes, based on HCl equiva- lents, are presented in Table 3-3. The predicted values for the chlorosilanes are comparable to the experimentally-derived 1-h LC50 values (log * log regression analysis of chlorosilane LC50 values vs. the number of chlorine groups yielded an r2 value of 0.97). The data suggest that the acute toxicity of the chlorosilanes is similar to or slightly less than what would be expected based on HCl molar

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116 Acute Exposure Guideline Levels equivalents. The within-class LC50 values were not significantly influenced by the number or type of hydrocarbon R-group(s) present (methyl, ethyl, propyl, or vinyl). Cases where the predicted value is less might be attributed to incomplete hydrolysis in the test atmosphere; however, continued hydrolysis and generation of HCl would be expected for any remaining chlorosilane when in contact with moist tissues (mucous membranes, lung) (Jean et al. 2006). This information taken in conjunction with the observed clinical signs suggests that the acute tox- icity of the chlorosilanes is quantitatively and qualitatively similar to HCl and that the HCl hydrolysis product is responsible for the acute toxicity of the chlo- rosilanes. TABLE 3-3 Measured and Predicted 1-Hour LC50 Values for Selected Chlorosilanes Measured Predicted Measured Predicted LC50 (ppm) (95% Ratio of Ratio of LC50 Compound confidence limits) LC50 (ppm) LC50 Values Values Hydrogen chloride 3,627 Tetrachlorosilane 1,312 (1,006-1,529) 3,627 ÷ 4 = 907 4:1 2.8:1 Propyl trichlorosilane 1,352 (1,254-1,455) 3,627 ÷ 3 = 1,209 3:1 2.7:1 Vinyl trichlorosilane 1,611 (1,505-1,724) 3,627 ÷ 3 = 1,209 3:1 2.3:1 Methyl trichlorosilane 1,365 (1,174-2,104) 3,627 ÷ 3 = 1,209 3:1 2.7:1 Ethyl trichlorosilane 1,257 (1,175-1,320) 3,627 ÷ 3 = 1,209 3:1 2.9:1 Methylvinyl 2,021 (1,806-2,257) 3,627 ÷ 2 = 1,814 2:1 1.8:1 dichlorosilane Dimethyl 2,092 (1,492-2,240) 3,627 ÷ 2 = 1,814 2:1 1.7:1 dichlorosilane Methyl 1,785 (1,671-1,963) 3,627 ÷ 2 = 1,814 2:1 2:1 dichlorosilane Trimethyl 4,257 (4,039-4,488) 3,627 ÷ 1 = 3,627 1:1 0.9:1 chlorosilane Dimethyl 4,478 (4,281-6,327) 3,627 ÷ 1 = 3,627 1:1 0.8:1 chlorosilane Source: Adapted from Jean et al. 2006.

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156 Acute Exposure Guideline Levels AEGL-1 VALUES FOR TRICHLOROSILANES 10 min 30 min 1h 4h 8h 0.60 ppm 0.60 ppm 0.60 ppm 0.60 ppm 0.60 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-1 values for trichlorosilanes were derived by adjusting the AEGL-1 values for HCl by the molar ratio of HCl to trichlorosilanes. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar Adjustment Factor: 3 Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-1 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-1 values for chlorosilanes is low, reflecting the lack of data on AEGL-1 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-1 effects of chlorosilanes would reduce uncertainty. AEGL-1 VALUES FOR TETRACHLOROSILANE 10 min 30 min 1h 4h 8h 0.45 ppm 0.45 ppm 0.45 ppm 0.45 ppm 0.45 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-1 values for tetrachlorosilane were derived by adjusting the AEGL-1 values for HCl by the molar ratio of HCl to tetrachlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 4 Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-1 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-1 values for chlorosilanes is low, reflecting the lack of data on AEGL-1 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-1 effects of chlorosilanes would reduce uncertainty.

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157 Selected Chlorosilanes AEGL-2 VALUES FOR MONOCHLOROSILANES 10 min 30 min 1h 4h 8h 100 ppm 43 ppm 22 ppm 11 ppm 11 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-2 values for HCl were adopted as AEGL-2 values for monochlorosilanes. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-2 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-2 values for chlorosilanes is moderate, reflecting the limited data on AEGL-2 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-2 effects of chlorosilanes would reduce uncertainty. AEGL-2 VALUES FOR DICHLOROSILANES 10 min 30 min 1h 4h 8h 50 ppm 22 ppm 11 ppm 5.5 ppm 5.5 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-2 values for dichlorosilanes were derived by adjusting the AEGL-2 values for HCl by the molar ratio of HCl to dichlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 2 Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-2 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-2 values for chlorosilanes is moderate, reflecting the limited data on AEGL-2 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-2 effects of chlorosilanes would reduce uncertainty.

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158 Acute Exposure Guideline Levels AEGL-2 VALUES FOR TRICHLOROSILANES 10 min 30 min 1h 4h 8h 33 ppm 14 ppm 7.3 ppm 3.7 ppm 3.7 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-2 values for trichlorosilanes were derived by adjusting the AEGL-2 values for HCl by the molar ratio of HCl to trichlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 3 Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-2 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-2 values for chlorosilanes is moderate, reflecting the limited data on AEGL-2 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-2 effects of chlorosilanes would reduce uncertainty. AEGL-2 VALUES FOR TETRACHLOROSILANE 10 min 30 min 1h 4h 8h 25 ppm 11 ppm 5.5 ppm 2.8 ppm 2.8 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-2 values for tetrachlorosilane were derived by adjusting the AEGL-2 values for HCl by the molar ratio of HCl to tetrachlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 4 Data adequacy: Mechanism-of-action data were considered adequate for the derivation of AEGL-2 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-2 values for chlorosilanes is moderate, reflecting the limited data on AEGL-2 end points after chlorosilane exposure and reliance on HCl data. Additional research on AEGL-2 effects of chlorosilanes would reduce uncertainty.

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159 Selected Chlorosilanes AEGL-3 VALUES FOR MONOCHLOROSILANES 10 min 30 min 1h 4h 8h 620 ppm 210 ppm 100 ppm 26 ppm 26 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press.. End point/Concentration/Rationale: AEGL-3 values for HCl were adopted as AEGL-3 values for monochlorosilanes. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Data adequacy: Data were considered adequate for the derivation of AEGL-3 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-3 values for chlorosilanes is high, reflecting the availability of lethality data on 11 of the 26 chlorosilanes considered and evidence for the role of HCl as the proximate toxicant. No additional research is needed on AEGL-3 end points. AEGL-3 VALUES FOR DICHLOROSILANES 10 min 30 min 1h 4h 8h 310 ppm 110 ppm 50 ppm 13 ppm 13 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-3 values for dichlorosilanes were derived by adjusting the AEGL-3 values for HCl by the molar ratio of HCl to dichlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 2 Data adequacy: Data were considered adequate for the derivation of AEGL-3 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-3 values for chlorosilanes is high, reflecting the availability of lethality data on 11 of the 26 chlorosilanes considered and evidence for the role of HCl as the proximate toxicant. No additional research is needed on AEGL-3 end points.

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160 Acute Exposure Guideline Levels AEGL-3 VALUES FOR TRICHLOROSILANES 10 min 30 min 1h 4h 8h 210 ppm 70 ppm 33 ppm 8.7 ppm 8.7 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-3 values for trichlorosilanes were derived by adjusting the AEGL-3 values for HCl by the molar ratio of HCl to trichlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 3 Data adequacy: Data were considered adequate for the derivation of AEGL-3 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-3 values for chlorosilanes is high, reflecting the availability of lethality data on 11 of the 26 chlorosilanes considered and evidence for the role of HCl as the proximate toxicant. No additional research is needed on AEGL-3 end points. AEGL-3 VALUES FOR TETRACHLOROSILANE 10 min 30 min 1h 4h 8h 160 ppm 53 ppm 25 ppm 6.5 ppm 6.5 ppm Key reference: NRC (National Research Council). 2004. Hydrogen chloride. Pp. 77-122 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 4. Washington, DC: National Academies Press. End point/Concentration/Rationale: AEGL-3 values for tetrachlorosilane were derived by adjusting the AEGL-3 values for HCl by the molar ratio of HCl to tetrachlorosilane. This approach is considered reasonable because qualitative and quantitative data on chlorosilanes suggest that the HCl hydrolysis product is largely responsible for the acute toxicity of the chlorosilanes. Molar adjustment factor: 4 Data adequacy: Data were considered adequate for the derivation of AEGL-3 values for chlorosilanes based on analogy to HCl. Confidence in the AEGL-3 values for chlorosilanes is high, reflecting the availability of lethality data on 11 of the 26 chlorosilanes considered and evidence for the role of HCl as the proximate toxicant. No additional research is needed on AEGL-3 end points.

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161 Selected Chlorosilanes APPENDIX E DERIVATION SUMMARY TABLES FOR HYDROGEN CHLORIDE (Excerpted from NRC 2004) Derivation Summary AEGL-1 VALUES FOR HYDROGEN CHLORIDE 10 min 30 min 1h 4h 8h 1.8 ppm 1.8 ppm 1.8 ppm 1.8 ppm 1.8 ppm Key reference: Stevens, B., J.Q. Koenig, V. Rebolledo, Q.S. Hanley, and D.S. Covert, D.S. 1992. Respiratory effects from the inhalation of hydrogen chloride in young adults with asthma. J. Occup. Med. 34(9): 923-929. Test species/Strain/Number: Human adults with asthma, 10 Exposure route/Concentrations/Durations: Inhalation at 0, 0.8, or 1.8 ppm for 45 min while exercising (1.8 ppm was determinant for AEGL-1) Effects: No treatment-related effects were observed in any of the individuals tested End point/Concentration/Rationale: The highest concentration tested was a no-effect level for irritation in a sensitive human population (10 asthmatic individuals tested) and was selected as the basis of AEGL-1. Effects assessed included sore throat, nasal discharge, cough, chest pain or burning, dyspnea, wheezing, fatigue, headache, unusual taste or smell, total respiratory resistance, thoracic gas volume at functional residual capacity, forced expiratory volume, and forced vital capacity. All subjects continued the requisite exercise routine for the duration of the test period. Uncertainty factors/Rationale: Total uncertainty factor: Interspecies: 1, test subjects were human Intraspecies: 1, test subjects were sensitive population (exercising asthmatic subjects) Modifying factor: Not applicable Animal-to-human dosimetric adjustment: Insufficient data Time-scaling: The AEGL-1 values for a sensory irritant were held constant across time because it is a threshold effect and prolonged exposure will not result in an enhanced effect. In fact one might become desensitized to the respiratory-tract irritant over time. Also, this approach was considered valid since the end point (no treatment-related effects at the highest concentration tested in exercising asthmatic subjects) is inherently conservative. Data quality and research needs: The key study was well-conducted in a sensitive human population and is based on no treatment-related effects. Additionally, the direct-acting irritation response is not expected to vary greatly among individuals. Therefore, confidence in the AEGL values is high.

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162 Acute Exposure Guideline Levels AEGL-2 VALUES FOR HYDROGEN CHLORIDE 10 min 30 min 1h 4h 8h 100 ppm 43 ppm 22 ppm 11 ppm 11 ppm Key references: Stavert, D.M., D.C. Archuleta, M.F. Behr, and B.E. Lehnert. 1991. Relative acute toxicities of hydrogen chloride, hydrogen fluoride, and hydrogen bromide in nose- and pseudo-mouth-breathing rats. Fundam. Appl. Toxicol. 16(4):636-655. (30-, 1-, 4-min and 8-h AEGLs) Barrow, C.S., Y. Alarie, M. Warrick, and M.F. Stock. 1977. Comparison of the sensory irritation response in mice to chlorine and hydrogen chloride. Arch. Environ. Health 32(2):68-76. (10-min AEGL) Test species/Strain/Number: F344 rats, 8 males/concentration (30-min, 1-, 4-, and 8-h); Male Swiss Webster mice (10-min) Exposure route/Concentrations/Durations: inhalation at 0 or 1,300 ppm for 30 min (1,300 ppm was determinant for 30-min, 1-, 4-, and 8-h AEGL-2) Effects (30-min, 1-, 4-, and 8-h): 0 ppm, no effects; 1,300 ppm, severe necrotizing rhinitis, turbinate necrosis, thrombosis of nasal submucosa vessels in nose-breathers; 1,300 ppm, severe ulcerative tracheitis accompanied by necrosis and luminal ulceration in mouth-breathers (determinant for AEGL-2); RD50 = 309 ppm (determinant for 10-min AEGL-2) End point/Concentration/Rationale: 1,300 ppm for 30 min; severe lung effects (ulcerative tracheitis accompanied by necrosis and luminal ulceration) or nasal effects (necrotizing rhinitis, turbinate necrosis, thrombosis of nasal submucosa vessels histopathology) in pseudo-mouth breathing male F344 rats (30-min, 1-, 4-, and 8-h); RD50 of 309 ppm ÷ 3 to estimate irritation (10-min) Uncertainty Factors/Rationale (30-min, 1-, 4-, and 8-h): Total uncertainty factor: 10 Intraspecies: 3, steep concentration-response curve implies limited individual variability. Interspecies: 3, use of an intraspecies uncertainty factor of 10 would bring the total uncertainty/modifying factor to 100 instead of 30. That would generate AEGL-2 values that are not supported by data on exercising asthmatic subjects, an especially sensitive subpopulation because exercise increases HCl uptake and exacerbates irritation. No effects were noted in exercising young adult with asthma exposed to HCl at 1.8 ppm for 45 min (Stevens et al. 1992). Using a total uncertainty factor of 30 would yield 4- and 8-h values of 3.6 ppm (instead of 11 ppm). It is not supportable to predict that humans would be disabled by exposure at 3.6 ppm for 4- or 8-h when exercising asthmatic subjects exposed to one-half this level for 45 min had no effects. The shorter time points would yield values 4- to 7 times above 1.8 ppm; however, the confidence in the time scaling for HCl is good for times up to 100 min because the value of n value was derived from a regression analysis of rat and mouse mortality data with exposure durations ranging from 1 min to 100 min. The 30-min value of 43 ppm derived with the total uncertainty factor of 10 is reasonable in light of the fact that baboons exposed to 500 ppm for 15 min experienced only a slightly increased respiratory rate. (Continued)

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163 Selected Chlorosilanes AEGL-2 VALUES FOR HYDROGEN CHLORIDE Continued 10 min 30 min 1h 4h 8h 100 ppm 43 ppm 22 ppm 11 ppm 11 ppm Modifying factor: 30-min, 1-, 4-, and 8-h AEGLs: 3 based on sparse database for AEGL-2 effects and that the effects observed at the concentration used as the basis for AEGL-2 values were somewhat severe. 10-min AEGL-2: the 10-min AEGL-2 value was derived by dividing the mouse RD50 of 309 ppm by a factor of 3 to obtain a concentration causing irritation (Barrow et al. 1977). One-third of the mouse RD50 for HCl corresponds to an approximate decrease in respiratory rate of 30%, and decreases in the range of 20% to 50% correspond to moderate irritation (ASTM 1991). Animal-to-human dosimetric adjustment: Insufficient data Time-scaling: Cn × t = k, where n=1, based on regression analysis of combined rat and mouse LC50 data (1 min to 100 min) reported by ten Berge et al. (1986). Data point used to derive AEGL-2 was 30 min. AEGL-2 values for 1-h exposure period was based on extrapolation from the 30-min value. The 4- and 8-h AEGL-2 values were derived by applying a modifying factor of 2 to the 1-h AEGL-2 value because time scaling would yield a 4-h AEGL-2 value of 5.4 ppm and an 8-h AEGL-2 of 2.7 ppm, close to the 1.8 ppm tolerated by exercising asthmatic subjects without adverse health effects. Data quality and research needs: Confidence is moderate since the species used is more sensitive than primates to the effects of HCl, the chemical is a direct- acting irritant, and a modifying factor was included to account for the relative severity of effects and sparse data base. AEGL-3 VALUES FOR HYDROGEN CHLORIDE 10 min 30 min 1h 4h 8h 620 ppm 210 ppm 100 ppm 26 ppm 26 ppm Key reference: Vernot, E.H., J.D. MacEwen, C.C. Haun, and E.R. Kinkead. 1977. Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicol. Appl. Pharmacol. 42(2):417-423. Wohlslagel, J., L.C. DiPasquale, and E.H. Vernot. 1976. Toxicity of solid rocket motor exhaust: Effects of HCl, HF, and alumina on rodents. J. Combust. Toxicol. 3:61-69. Test species/Strain/Sex/Number: Sprague-Dawley rats, 10 males per concentration Exposure route/Concentrations/Durations: inhalation at 0, 1,813, 2,585, 3,274, 3,941, or 4,455 ppm for 1 h (Continued)

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164 Acute Exposure Guideline Levels AEGL-3 VALUES FOR HYDROGEN CHLORIDE Continued 10 min 30 min 1h 4h 8h 620 ppm 210 ppm 100 ppm 26 ppm 26 ppm Effects: Concentration Mortality 0 ppm 0/10 1,813 ppm 0/10 2,585 ppm 2/10 3,274 ppm 6/10 3,941 ppm 8/10 4,455 ppm 10/10 LC50: reported as 3,124 ppm (determinant for AEGL-3) End point/Concentration/Rationale: One-third of the 1-h LC50 (3,124 × 1/3 = 1,041 ppm) to estimate a concentration causing no deaths. Uncertainty factors/Rationale: Total uncertainty factor: 10 Intraspecies: 3, a steep concentration-response curve implies limited individual variability. Interspecies: 3, (1) the steep concentration-response curve for lethality observed in the Wohlslagel et al. (1976) study in which 1,041 ppm (one-third of the LC50 of 3,124 ppm) was lower than the LC0 of 1,813 ppm. This is a conservative selection of the LC0 and the steep concentration-response curve argues for little interindividual variability; (2)AEGL-3 values generated from a total uncertainty factor of 30 would be close to the AEGL-2 values (within a factor of 2) generated above which are reasonable when compared with data on exercising asthmatic subjects; (3) Sellakumar et al. (1985) exposed rats to 10 ppm of HCl for 6 h/day, 5 days/week for life and only observed increased trachael and laryngeal hyperplasia. The estimated 6-h AEGL-3 using an intraspecies uncertainty factor of 3 is 17 ppm, close to the level used in the lifetime study in which only mild effects were induced; and (4) rats exposed at 50 ppm for 6 h/day, 5 days/week for 90 days exhibited mild rhinitis (Toxigenics Inc. 1984). This level is already 2 times that of the AEGL-3 value for death. Thus, the total uncertainty factor is 10. Modifying factor: Not applicable Animal-to-human dosimetric adjustment: Insufficient data Time-scaling: Cn × t = k, where n = 1, based on regression analysis of rat and mouse mortality data (1 min to 100 min) reported by ten Berge et al. (1986). Reported 1-h data point was used to derive AEGL-3 values. AEGL-3 values for 10-min, 30-min, and 4-h were based on extrapolation from the 1-h value. The 4-h value was adopted as the 8-h value. Data quality and research needs: Study is considered appropriate for AEGL-3 derivation because exposures are over a wide range of HCl concentrations and utilize a sufficient number of animals. Data were insufficient to derive a no-effect level for death. One-third of the LC50 has been utilized previously for chemicals with steep concentration-response curves. Also, in the key study, no deaths were observed in rats exposed at 1,813 ppm.

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165 Selected Chlorosilanes APPENDIX F CATEGORY PLOTS FOR SELECTED CHLOROSILANES Chemical Toxicity - Rat LC50 Data Monochlorosilanes* 10000 Human - No Effect Human - Discomfort 1000 Human - Disabling Animal - No Effect ppm 100 Animal - Discomfort AEGL-3 Animal - Disabling AEGL-2 10 Animal - Partially Lethal Animal - Lethal AEGL-1 AEGL 1 0 60 120 180 240 300 360 420 480 Minutes FIGURE F-1 Category plot for monochlorosilanes. *Data plotted are for trimethyl chlo- rosilane and dimethyl chlorosilane. Chemical Toxicity - Rat LC50 Data Dichlorosilanes* 10000 Human - No Effect Human - Discomfort 1000 Human - Disabling Animal - No Effect 100 ppm Animal - Discomfort AEGL-3 10 Animal - Disabling AEGL-2 Animal - Partially Lethal 1 AEGL-1 Animal - Lethal AEGL 0 0 60 120 180 240 300 360 420 480 Minutes FIGURE F-2 Category plat of dichlorosilanes. *Data plotted are for methylvinyl dichlo- rosilane, dimethyl dichlorosilane, and methyl dichlorosilane.

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166 Acute Exposure Guideline Levels Chemical Toxicity - Rat LC50 Data Trichlorosilanes* 10000 Human - No Effect Human - Discomfort 1000 Human - Disabling Animal - No Effect 100 ppm Animal - Discomfort AEGL-3 10 Animal - Disabling AEGL-2 Animal - Partially Lethal AEGL-1 1 Animal - Lethal AEGL 0 0 60 120 180 240 300 360 420 480 Minutes FIGURE F-3 Category plot for trichlorosilanes. *Data plotted are for propyl trichlorosi- lane, vinyl trichlorosilane, methyl trichlorosilane, and ethyl trichlorosilane. Chemical Toxicity - Rat Lethality Data Tetrachlorosilane 10000 Human - No Effect Human - Discomfort 1000 Human - Disabling Animal - No Effect 100 ppm Animal - Discomfort AEGL-3 10 Animal - Disabling AEGL-2 Animal - Partially Lethal 1 Animal - Lethal AEGL-1 AEGL 0 0 60 120 180 240 300 360 420 480 Minutes FIGURE F-4 Category plot for tetrachlorosilane.