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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: 75-07-0; Chemical Formula: CH3CHO

OSHA’s previous PEL for acetaldehyde was 200 ppm as an 8-hour TWA. In its NPRM, OSHA proposed revising its limit for acetaldehyde to 100 ppm as an 8-hour TWA and supplementing this with a STEL of 150 ppm; these are the limits currently recommended by the ACGIH. OSHA is establishing permissible exposure limits of 100 ppm as an 8-hour TWA and 150 ppm as a 15-minute STEL in the final rule. Acetaldehyde is a colorless liquid with a pungent, fruity odor.

The 200-ppm 1968 TLV established by the ACGIH for acetaldehyde was based on a sensory irritation study conducted by Silverman, Schulte, and First (1946/Ex. 1-142) that showed that unacclimatized individuals experienced eye irritation at 50 ppm, but that a level of 200 ppm was tolerable for an 8-hour day. Reexamination of the data reported by Silverman, Schulte, and First (1946/Ex. 1-142) reveals that, at 200 ppm of acetaldehyde, all exposed persons experienced inflammation of the conjuctivae of the eyes, which manifested as redness. OSHA therefore concluded that its previous PEL of 200 ppm placed exposed employees at risk of conjunctivitis and other irritation and that a reduction to 100 ppm was necessary to reduce this risk. OSHA also proposed a STEL of 150 ppm to supplement the 8-hour limit because, without a STEL, workers could be exposed to levels many times those that have been shown to cause corneal injury, sensitization, and respiratory tract irritation. NIOSH (Ex. 8-47, Table N6B; Tr. pp. 3-97 to 3-98) indicated that acetaldehyde might be a candidate for an individual 6(b) rulemaking. As pointed out by the Workers Institute for Safety and Health (WISH) (Tr. 7-117, Ex. 116, p. 8), IARC has classified acetaldehyde as a possible human carcinogen based an animal data. There is also evidence that acetaldehyde is teratogenic and fetotoxic in animals (Ex. 116). The Agency will continue to monitor the scientific evidence for this substance to examine whether a further reduction in the PEL is warranted.

OSHA concludes that employees are placed at significant risk of conjunctivitis and irritation at the current 8-hour TWA limit of 200 ppm. The Agency has determined that conjunctivitis and sensory irritation represent material impairments of health or functional capacity. Therefore, OSHA is revising the limit for acetaldehyde to 100 ppm as an 8-hour TWA and 150 ppm as a 15-minute STEL to substantially reduce this risk.