The "green" movement has resulted in the introduction of several new "environmentally-friendly" substitutes into commerce, including 1-bromopropane (1-BP; CAS no. 106-94-5). Although use of 1-BP is intended to minimize ozone depletion, occupational exposure is of concern. Case studies, occupational exposure assessments, and epidemiological investigations have suggested that workplace exposure to 1-BP may be associated with neurological, reproductive, and hematological effects. Previous quantitative risk assessments of 1-BP have been based on toxicological studies of these and other non-cancer endpoints. This poster presents a quantitative risk assessment based on a NTP chronic bioassay, in which rats and mice were exposed to 125-500 or 62.5-250 ppm 1-BP, respectively, for up to 2 years. Inhalation of 1-BP produced alveolar/bronchiolar adenomas and carcinomas in female mice, adenomas of the large intestine in female rats, and keratoacanthoma/squamous cell carcinoma of the skin in male rats. Benchmark concentrations (BMC) and lower 95% confidence limits (BMCL) estimates at the 1 in 1000 response level (0.1%) were based on a previously published model average procedure. The BMC (BMCL) estimates were 0.85 (0.41) ppm for alveolar/bronchiolar adenoma + carcinoma; 13.5 (2.76) ppm for large intestine adenomas; and 3.73 (1.44) ppm for keratoacanthoma +squamous cell carcinoma of the skin. The BMC (BMCL) estimates were extrapolated to humans on a (body weight)0.75 basis, assuming a 45-year occupational exposure. Human-equivalent concentrations for a 1 in a 1000 lifetime added risk at the various tumor sites are 0.39 (0.19) ppm, for lung tumors; 6.17 (1.26) ppm for intestinal tumors; and 1.75 (0.68) ppm for skin tumors. These results suggest that even sub-ppm occupational exposures to 1-BP may pose an increased risk of cancer.
Toxicology; Risk-analysis; Exposure-assessment; Epidemiology; Quantitative-analysis; Propanes; Biological-effects; Bioassays; Chronic-exposure; Laboratory-animals; Carcinomas; Alveolar-cells; Bronchial-cancer; Intestinal-cells; Tumors; Cell-alteration; Cell-transformation; Glandular-disorders; Skin-disorders; Skin-tumors; Dose-response; Lung-disease; Humans; Lifespan; Cancer
The Toxicologist. Society of Toxicology 52nd Annual Meeting and ToxExpo, San Antonio, Texas, March 10-14, 2013