1,1-DICHLOROETHANE

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: 75-34-3; Chemical Formula: CH₃CHCl₂

The current OSHA limit for 1,1-dichloroethane, which is a hepatotoxin, is 100 ppm TWA. The ACGIH TLV-TWA is 200 ppm, with a 250 ppm STEL; NIOSH has no REL for this substance. The previous ACGIH TLV of 100 ppm was based on the observation that 1,1-dichloroethane has an acute toxicity approximately half that of carbon tetrachloride and a chronic toxicity somewhat less than that of carbon tetrachloride (for which a TLV of 10 ppm had been set). In 1973, the ACGIH adopted the higher 200-ppm TLV based on unpublished data from the Dow Chemical Company (AIHA 1971, as cited in ACGIH 1986/Ex. 1-3, p. 184) showing that rats, rabbits, guinea pigs, and dogs exhibited no gross or microscopic organ pathology after exposure to 500 or 1000 ppm of 1,1-dichloroethane for six months. The ACGIH cited no human data in support of its increase in the TLV. NIOSH (Ex. 8-47, Table N1) concurs that OSHA’s 100-ppm 8-hour TWA is appropriate. OSHA received no other comments on 1,1-dichloroethane.

Because no human toxicity data are available for 1,1-dichloroethane and because the Dow data are unpublished and thus not available for scrutiny, OSHA concludes that the evidence for this substance is insufficient to warrant increasing the PEL at this time.