OSHA formerly had an 8-hour TWA PEL of 0.1 ppm (0.25 mg/m3) for acrolein. OSHA proposed the addition of a 0.3-ppm STEL to this TWA limit, and the final rule adopts this short-term limit. NIOSH (Ex. 8-47, Table N1) concurred with these proposed limits. These limits for acrolein are the same as those recommended by the ACGIH (1986/Ex. 1-3). Acrolein is a colorless or yellowish flammable liquid with a disagreeable, choking odor.
In early inhalation studies of cats (Iwanoff 1911, as cited in ACGIH 1986/Ex. 1-3, p. 11), exposure to 10 ppm acrolein for 3.5 hours was found to have only transient effects, including salivation, lacrimation, respiratory irritation, and mild narcosis. However, later studies reported that an exposure to 1 ppm of acrolein produced marked nose and eye irritation in five minutes or less (Cook 1945/Ex. 1-726). Over longer periods, studies have demonstrated fatalities in one of six rats exposed for four hours to airborne concentrations of acrolein at 8 ppm; at 16 ppm, the mortality was 100 percent (Smyth 1956/Ex. 1-759). Irritation of the upper respiratory tract is the primary symptom of acrolein inhalation, but lung edema can occur after exposure to high concentrations (Henderson and Haggard 1943a/Ex. 1-881). In addition, skin contact with acrolein causes skin burns and severe injury to the cornea.
No comments (other than NIOSH's) were received on OSHA's proposed 8-hour time-weighted-average limit or its 15-minute short-term limit of 0.3 ppm. OSHA concludes that, in the absence of a STEL, the current 0.1-ppm TWA limit would not protect employees from short-term exposures to airborne concentrations in excess of 1 ppm, the level found by Cook (1945/Ex. 1-726) to cause severe eye and nose irritation. OSHA considers these adverse effects to represent material impairments of health or functional capacity. Therefore, OSHA finds that the 0.3-ppm STEL is necessary to protect employees from the significant risk associated with mucous membrane irritation, and the Agency is revising the exposure limit for acrolein to 0.1 ppm as an 8-hour TWA and 0.3 ppm as a 15-minute STEL.