PHOSPHORUS OXYCHLORIDE

OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.

CAS: 10025-87-3; Chemical Formula: POCl₃

OSHA had no former limit for phosphorus oxychloride. The ACGIH has a TLV-TWA of 0.1 ppm and a TLV-STEL of 0.5 ppm for this clear, colorless, fuming liquid, which has a pungent odor. The proposed PELs were 0.1 ppm as an 8-hour TWA and 0.5 ppm as a 15-minute STEL. NIOSH (Ex. 8-47, Table N1) concurred with these limits. The final rule establishes an 8-hour TWA of 0.1 ppm for this substance but, for the reasons discussed below, does not include a STEL for phosphorus oxychloride.

The primary hazards associated with inhalation of phosphorus oxychloride vapor are irritation of the eyes and respiratory tract, as well as narcotic effects, gastric irritation, pulmonary edema, and nephritis (International Technical Information Institute 1978/Ex. 1-837).

Weeks and associates (1964, as cited in ACGIH 1986/Ex. 1-3, p. 485) reported 4-hour LC(50) values for phosphorus oxychloride of 48 ppm and 52 ppm for rats and guinea pigs, respectively. They also observed that ammonia vapor mediates the irritant effects of exposure to phosphorus oxychloride without significantly altering this LC(50) value (Weeks, Downing, Musselman et al. 1964, as cited in ACGIH 1986/Ex. 1-3, p. 485).

Both chronic and acute occupational intoxication have been reported to occur among workers exposed to phosphorus oxychloride (Sassi 1954/Ex. 1-931).

The American Industrial Hygiene Association (AIHA) recommended that OSHA delete the STEL for phosphorus oxychloride (Tr. 3-307, Ex. 8-16) on the grounds that the ACGIH intends to delete this STEL. After a review of the available evidence for this substance, OSHA is not including a STEL for phosphorus oxychloride in the final rule. The Agency’s reasoning on this issue is discussed in Section VI.C.17 of this preamble.

In the final rule, OSHA is establishing a PEL of 0.1 ppm (8-hour TWA) for phosphorus oxychloride, by analogy to the toxicity of phosphorus trichloride. The Agency concludes that this limit will reduce the significant risk of narcosis and systemic poisoning, which are material health impairments that are associated with acute and chronic exposure at levels above the new PEL.