ETHYL BENZENE

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: 100-41-4; Chemical Formula C₈H₁₀

OSHA’s former limit for ethyl benzene was 100 ppm as an 8-hour TWA. Based on the skin and mucous membrane irritant properties associated with exposure to ethyl benzene, OSHA proposed permissible exposure limits for this substance of 100 ppm as an 8-hour TWA and 125 ppm as a 15-minute STEL. NIOSH (Ex. 8-47, Table N1) concurred with this proposal. The final rule establishes limits of 100 ppm TWA and 125 ppm STEL for ethyl benzene; these limits are consistent with the ACGIH recommendation. Ethyl benzene is a colorless, flammable liquid with an aromatic odor.

The Agency’s decision to add a STEL to the existing time-weighted average limit reflects evidence that transient eye irritation occurs in humans at vapor concentrations of 200 ppm; the short-term limit is necessary to protect exposed workers from the risk of such irritation as a result of even brief excursions above the 100-ppm level.

Written comments submitted by ARCO Chemical Company (ACC) (Ex. 3-638) include a detailed discussion of ethyl benzene’s toxicity in animals, as reported in several recent studies (ECETOC 1986; Dynamac Corporation 1986) and in a personal communication from the National Toxicology Program’s Chemical Manager for Ethyl Benzene. The findings of these investigators include: moderate dermal irritation on intact and abraded rabbit skin after a 24-hour application; mild conjunctival irritation (without corneal effects) from direct instillation of undiluted ethyl benzene in rabbit eyes; erythema and edema with superficial necrosis, resulting in exfoliation of large patches of skin, following repeated and prolonged application of the undiluted material to rabbit skin; “a slight, cloudy swelling of hepatocytes” in animals subchronically exposed to the vapor as a “result of an increase in the endoplasmic reticulum (SER), which is an adaptive process responsible for increased microsomal enzyme activity and, presumably, increased metabolism of ethyl benzene”; congestion of the lungs, nasal mucosa, liver, and kidneys in mice and rats exposed six hours/day for four consecutive days to ethyl benzene concentrations of 2360 ppm and in mice exposed to 1190 ppm; and lacrimation and salivation in rats exposed at 400 and 800 ppm for six hours/day, five days/week (ECETOC 1986 and Dynamac Corporation 1986, both as cited in Ex. 3-638). ACC stressed the fact that, except at very high concentrations, significant systemic toxicity does not appear to be a manifestation of ethyl benzene exposure.

In addition to providing the results of these up-to-date studies on the health effects in animals of ethyl benzene exposure, the ACC indicated its support for both the retention of the current 100-ppm TWA limit and the adoption of a 125-ppm 15-minute STEL for ethyl benzene. Both concentrations, according to the ACC, “provide a wide safety margin for eye irritation compared to the concentration which can be tolerated in the workplace (1000 ppm).”

The New Jersey Department of Health (Exs. 144, 144A) urged OSHA to set a PEL for ethyl benzene on the basis of EPA’s IRIS data. The use of such an approach is discussed in Section VI.A of the preamble.

OSHA concludes that workers exposed to concentrations of ethyl benzene above the 100-ppm level, even briefly, are at significant risk of experiencing irritation; the Agency considers this to be a material impairment of health. Accordingly, the Agency is establishing a short-term limit of 125 ppm for a 15-minute period to supplement the existing 100-ppm time-weighted-average limit for ethyl benzene.