Inhalation toxicity of hexafluoroisobutylene

An acute study of hexafluoroisobutylene (HFIB) determined its 4-hr LC50 in rats to be 1425 ppm. In a 2-week study, all animals exposed to 215 ppm for 4 days died or were sacrificed in extremis, while those exposed to the lowest level tested, 53 ppm, showed respiratory and renal effects. Based on the results of these studies, Fischer-344 rats were exposed 6 hr a day, 5 days a week, for 13 weeks to average HFIB concentrations of 3, 10, 30, and 90 ppm. No animals died due to the HFIB exposures. However, at the highest exposure level tested there were numerous marked signs of systemic toxicity in males and females. At all exposure levels, males were more affected than females. The lungs and kidneys were clearly target organs for HFIB, the kidneys being more sensitive in this study (having increased absolute and relative weights, alterations in relevant clinical chemistry parameters, and alterations in microscopic structure). A clear dose-response pattern for the above toxic effects was evident with 10 ppm in the males being an effect level. Male rats exposed to 30 ppm of HFIB had decreased body weights and significantly increased kidney weights. A satellite group of animals was maintained for 2 weeks after the completion of exposure. These animals showed some remission from the observed toxic effects, indicating recovery could be expected in rats from at least most of the toxic effects associated with exposure to HFIB. All effects observed in 3 ppm males disappeared by the end of the recovery period.