Characterization of inhaled alpha-methylstyrene vapor toxicity for B6C3F1 mice and F344 rats

alpha-Methylstyrene (AMS) is a chemical intermediate used in the synthesis of specialty polymers and copolymers. Inhalation studies of AMS were conduc ted because of the lack of toxicity data and the structural similarity of A MS to styrene, a toxic and potentially carcinogenic chemical. Male and fema le B6C3F1 mice were exposed to 0, 600, 800, or 1000 ppm AMS 6 h/day, 5 days /week, for 12 days. After 1 exposure, 21% (5/24) of female mice were found dead in the 1000-ppm group, 56% (10/18) in the 800-ppm group, and 6% (1/18) in the 600-ppm concentration group. After 12 exposures, relative liver wei ghts were significantly increased and relative spleen weights were signific antly decreased in both male and female mice at all concentrations. No micr oscopic treatment-related lesions were observed. A decrease in hepatic glut athione (GSH) was associated with AMS exposure for 1 and 5 days. Male and f emale F344 rats were exposed to 0, 600 or 1000 ppm AMS for 12 days. No mort ality or sedation occurred in AMS-exposed rats. Relative liver weights were significantly increased in both males and females after 12 exposures to 60 0 or 1000 ppm. An increased hyaline droplet accumulation was detected in ma le rats in both concentration groups; no significant microscopic lesions we re observed in other tissues examined. Exposure of male and female F344 rat s and male NBR rats to 0, 125, 250 or 500 ppm AMS, 6 h/day for 9 days resul ted in increased accumulation of hyaline droplets in the renal tubules of m ale F344 rats in the 250 and 500 ppm concentration groups. Although AMS and styrene are structurally very similar, AMS was considerably less toxic for mice and more toxic for male rats than styrene.