ACRYLONITRILE - A REEVALUATION OF THE DATABASE TO SUPPORT AN INHALATION CANCER RISK ASSESSMENT

Acrylonitrile (ACN) is a monomer used extensively in the production of plastics, synthetic fibers, and rubber. In previous assessments condu cted by IARC and the EPA, ACN was classified as a probable human carci nogen based on limited evidence in humans and sufficient evidence in l aboratory animals. Specifically, EPA had determined that there was an association between ACN exposure and lung cancer based on a study by O 'Berg (1980, J. Occup. Med. 22, 245-252). However, a follow-up of this cohort (O'Berg et al., 1985, J. Occup. Med. 27, 835-840) shows no sta tistically significant excess of lung cancer mortality or incidence. O ur evaluation of the more recent human database taken as a whole shows that there is not a clear association between ACN exposure and human cancer, yet the studies have insufficient power to be able to rule out a small increase. In laboratory rats, however, ACN has been shown to be clearly carcinogenic by the oral and inhalation routes. Applying th e methodology of EPA's proposed 1996 cancer risk assessment guidelines to the rat tumor data, the estimated upper bound on the excess lifeti me risk at continuous exposure to 1 mu g/m(3) ACN is calculated to be in the range of 8.2 x 10(-6) to 1.1 X 10(-5). (C) 1997 Academic Press.