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CHLORINE TRIFLUORIDE

BACKGROUND INFORMATION

PHYSICAL AND CHEMICAL PROPERTIES

Chemical formula:

ClF3

Molecular weight:

92.46

CAS number:

7790–91–2

Melting point:

−80 to −83° C

Boiling point:

11.2–11.75°C

Density:

1.8403 g/ml (15°C)

General characteristics:

May exist as white solid, colorless to pale yellow-green liquid, or practically colorless gas; sweet suffocating odor; odor threshold very low, but not accurately known (Cloyd and Murphy, 1965); vapor phase decomposes into Cl2, ClF, ClOF, ClO2, and HF, depending on availability of water

Conversion factors:

1 ppm =3.78 mg/m3

1 mg/m3 =0.26 ppm

OCCURRENCE AND USE

Chlorine trifluoride is used as a fluorinating agent, in nuclear-fuel processing, as an incendiary, and as an igniter and propellant for rockets (Windholz et al., 1976). It is prepared by reaction of chlorine and fluorine at 280°C and condensation of the product at −80°C. The product obtained is 99.0% pure (Hawley, 1977). Dost et al. (1974) noted the instability of chlorine trifluoride and the potential diversity of its hydrolysis products.

SUMMARY OF TOXICITY INFORMATION

EFFECTS ON HUMANS

At high concentations (detectable by odor), exposure can cause gasping, swelling of the eyes and eyelids, cloudiness of the cornea, lacrimation, severe salivation, coughing, breathing difficulties, and convulsions within a few minutes (Cloyd and Murphy, 1965). Damage to the eyes is said to be permanent (Leins, undated). Concentrations high enough to be fatal would be so irritating to eyes, throat, and lungs as to be intolerable. The halogen-pungent odor of chlorine trifluoride can be detected at sufficiently low concentrations that exposed personnel may not experience adverse effects if they evacuate the area immediately (Cloyd and Murphy, 1965). Contact with skin causes severe burns and ulcers that are difficult to heal (Cloyd and Murphy, 1965; Leins, undated). The tissue destruction is caused by



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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2 CHLORINE TRIFLUORIDE BACKGROUND INFORMATION PHYSICAL AND CHEMICAL PROPERTIES Chemical formula: ClF3 Molecular weight: 92.46 CAS number: 7790–91–2 Melting point: −80 to −83° C Boiling point: 11.2–11.75°C Density: 1.8403 g/ml (15°C) General characteristics: May exist as white solid, colorless to pale yellow-green liquid, or practically colorless gas; sweet suffocating odor; odor threshold very low, but not accurately known (Cloyd and Murphy, 1965); vapor phase decomposes into Cl2, ClF, ClOF, ClO2, and HF, depending on availability of water Conversion factors: 1 ppm =3.78 mg/m3 1 mg/m3 =0.26 ppm OCCURRENCE AND USE Chlorine trifluoride is used as a fluorinating agent, in nuclear-fuel processing, as an incendiary, and as an igniter and propellant for rockets (Windholz et al., 1976). It is prepared by reaction of chlorine and fluorine at 280°C and condensation of the product at −80°C. The product obtained is 99.0% pure (Hawley, 1977). Dost et al. (1974) noted the instability of chlorine trifluoride and the potential diversity of its hydrolysis products. SUMMARY OF TOXICITY INFORMATION EFFECTS ON HUMANS At high concentations (detectable by odor), exposure can cause gasping, swelling of the eyes and eyelids, cloudiness of the cornea, lacrimation, severe salivation, coughing, breathing difficulties, and convulsions within a few minutes (Cloyd and Murphy, 1965). Damage to the eyes is said to be permanent (Leins, undated). Concentrations high enough to be fatal would be so irritating to eyes, throat, and lungs as to be intolerable. The halogen-pungent odor of chlorine trifluoride can be detected at sufficiently low concentrations that exposed personnel may not experience adverse effects if they evacuate the area immediately (Cloyd and Murphy, 1965). Contact with skin causes severe burns and ulcers that are difficult to heal (Cloyd and Murphy, 1965; Leins, undated). The tissue destruction is caused by

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2 oxidation of tissues, thermal damage from the heat of oxidation, and the effects of HF formed (Cloyd and Murphy, 1965). In the only documented human exposure, a worker was exposed to the effluent of a chlorine trifluoride-charcoal reactor when he was eating lunch approximately 200 ft downwind from the disposal system. The exposure lasted about 1–2 min. He reported to the medical clinic with symptoms of frontal headache, a bad taste, abdominal pain, and breathing difficulty that persisted for some 2 h. A physician treated him with oxygen therapy for 0.5 h and with APCs (a mixture of aspirin, phenacetin, and caffeine) and the symptoms were relieved. No systemic or local effects were found. The patient reported for work the next day, with no apparent after-effects except fatigue (Longley et al., 1965). EFFECTS ON ANIMALS Rats exposed in a dynamic-flow chamber to chlorine trifluoride at 400 ppm died within 40 min; at 800 ppm, the LT50 (lethal time for 50% of the animals) was 15 min. Inhalation exposure of rats at 800 ppm for 15 min was always lethal, whereas exposure at 400 ppm was usually lethal after 35 min of exposure (Dost et al., 1974). In another experiment, 1-h exposure to chlorine trifluoride led to LC50s of 299 (260–344) ppm in male rats and 178 (169–187) ppm in mice (Vernot et al., 1977). In extensively described experiments, rats were exposed at 480, 96, and 21 ppm; two dogs were also exposed at 21 ppm (Horn and Weir, 1955). The LT50 at 480 ppm was 40 min; at 96 ppm, it was 3.7 h. At 480 ppm, the rats immediately exhibited increased activity. After 2 min, rhinorrhea was noted. From then on, symptoms of respiratory difficulty, eye irritation, and excessive salivation developed. Within 20 min, all were in “acute distress.” In several rats, the cornea looked dull and milky-white where it was not protected by the eyelid. All rats died within 70 min; death was usually preceded by excitement and occasionally by convulsions and coma. The same signs developed, at a lower rate, in the rats exposed at 96 ppm. After 4.5 h of exposure, 70% of the animals were dead. Shortly after the survivors were removed from the chamber, two more died (total mortality, 80%). Some showed excitement and “tonic movements” before death. The gross pathology of the lungs from the animals exposed at 480 and 96 ppm was the same: emphysema, pulmonary edema, vascular congestion, and fusion of the lining cells of the bronchi into a hyaline membrane. The livers exhibited hydropic degeneration and marked vascular congestion. In the 96-ppm group, only the gastrointestinal tract was markedly distended with gas. Rats and dogs were exposed at 21 ppm 6 h/d for 2 d. About 10 min after exposure began, the dogs had rhinorrhea and lacrimation and kept their eyes tightly closed. During the first day, they coughed up mucous material and had rapid respiration and excessive salivation. When removed from the chamber, they refused to eat or drink, and they kept their eyes tightly closed. The conjunctivae were markedly injected. The animals’ fur felt as though it had been “singed.” Toxic signs also appeared early in the rats, with preening and rhinorrhea. By the end of the first day, rhinorrhea and lacrimation

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2 were observed. By the next morning, the animals were essentially normal, except that the dogs’ eyes were still markedly inflamed. The second day of the exposure followed the same course as the first up to 4.5 h after starting. The exposure was then halted, because the exhaust system had become plugged and air flow had decreased. The concentration at which the animals had been exposed was not determined, but certainly had risen somewhat. After removal from the chamber, one dog developed severe bilateral corneal ulcers, which had re-epithelialized after a month. Within a few days, all the animals were essentially normal, except for the presence of corneal ulcers in one dog. Horn and Weir (1955) also exposed two dogs and 20 rats to chlorine trifluoride at an average concentration of 5.15 ppm for 6 h/d, 5 d/wk, for 6 wk (31 exposures). The same signs developed over the first several days as had after acute exposure, but they were less severe. By the midpoint of the experiment, some respiratory distress developed; one dog died after 17 d, and another on the twenty-sixth day. Both apparently died of pneumonia, although penicillin therapy was given to the second. Only one rat died during the experiment; its death was preceded by a convulsion. All others appeared to be in poor health. All the animals that died had bronchopneumonia, bronchiectasis, purulent bronchiolitis, and lung abscesses. Those killed at the end of the experiment had lung hyperemia, hemorrhage, and edema. The kidneys and livers showed vascular congestion. In a chronic exposure study, 20 rats and two dogs were exposed to chlorine trifluoride at an average concentration of 5.15 ppm for 6 h/d, 5 d/wk, for 6 mo (Horn and Weir, 1956). At the start of the experiment, the dogs exhibited the early signs of irritation, but the rats appeared unaffected and quiet. Recovery was complete overnight. By the ninth day, the rats started preening immediately after exposure began; they then became “depressed” and remained so for the rest of the exposure period. One-fourth of the rats died during the experiment. Autopsy of these rats showed pulmonary edema and bronchopneumonia. The animals that survived showed essentially the same signs as were seen in the subacute exposures. On autopsy, pulmonary irritation was observed. One dog died on day 115 of the experiment of purulent bronchitis and pulmonary abscesses. The other had alveolar hemorrhage, interstitial edema, and pulmonary irritation on autopsy. INHALATION EXPOSURE LIMITS The ACGIH has established a ceiling limit for chlorine trifluoride of 0.1 ppm (approximately 0.4 mg/m3) (ACGIH, 1980, 1983). Its recommendation noted that this limit is probably low enough to prevent development of serious injury, but the suitability of the limit requires further evaluation in controlled worker exposure. COMMITTEE RECOMMENDATIONS The toxicology of chlorine trifluoride was reviewed originally by the Committee on Toxicology in 1962 and updated in 1968.

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2 The only new information that was not available to the Committee at the previous updating deals with the acute toxicity of the compound by inhalation. The determined values are consistent with previous data. Therefore, there appears to be no reason to change the previously established exposure limits. However, as stated by ACGIH, data are still needed on controlled exposure of workers in occupational settings. The present Committee’s recommended EELs for chlorine trifluoride and the limits proposed in 1968 are shown below.   1968 1984 10-min EEL 7 ppm 7 ppm 30-min EEL 3 ppm 3 ppm 60-min EEL 1 ppm 1 ppm

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2 REFERENCES American Conference of Governmental Industrial Hygienists. 1980. Chlorine trifluoride. Documentation of the Threshold Limit Values. 4th ed. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists. p. 81–82. American Conference of Governmental Industrial Hygienists. 1983. TLVs(R). Threshold Limit Values for Chemical Substances and Physical Agents in Work Environment with Intended Changes for 1983–1984. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists. 93 p. Cloyd, D.R., and Murphy, W.J. 1965. Handling of Hazardous Materials. Technology Survey. Washington, D.C.: National Aeronautics and Space Administration. 93 p. Dost, F.N., Reed, D.J., Smith, V.N., and Wang, C.H. 1974. Toxic properties of chlorine trifluoride. Toxicol. Appl. Pharmacol. 27: 527–536. Hawley, G.G. 1977. The Condensed Chemical Dictionary. 9th ed. New York: Van Nostrand Reinhold Co. p. 192. Horn, H.J., and Weir, R.J. 1955. Inhalation toxicology of chlorine trifluoride. I. Acute and subacute toxicity. AMA Arch. Ind. Health 12:515–521. Horn, H.J., and Weir, R.J. 1956. Inhalation toxicology of chlorine trifluoride. II. Chronic toxicity. AMA Arch. Ind. Health 13:340–345. Leins, J.A. 1961. Aero-jet General Corporation Test Operations. Safety Procedure No. 26. Aero-jet General Corp., California. 9 p. Longley, M.Y., Pierce, J.F., and Griesemer, E.C. 1965. (U) A toxic hazard study of selected missile propellants (1965). AMRL-TR-65–99. Wright-Patterson Air Force Base, Ohio: Aerospace Medical Research Laboratories. 87 p. Vernot, E.H., MacEwen, J.D., Haun, C.C., and Kinkead, E.R. 1977. Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicol. Appl. Pharmacol. 42:417–423. Windholz, M., Budavari, S., Stroumtsos, L.Y., and Fertig, M.N., eds. 1976. The Merck Index: An Encyclopedia of Chemicals and Drugs. 9th ed. Rahway, New Jersey: Merck & Co., Inc. p. 266.