1,3-Butadiene: exposure estimation, hazard characterization, and exposure-response analysis

Area of Science:

• Environmental Health
• Toxicology
• Occupational Health

Background:

• 1,3-Butadiene is a priority substance in Canada, with general population exposure mainly via ambient air.
• Inhalation of 1,3-butadiene is carcinogenic in rodents, inducing tumors and genotoxicity.
• Occupational exposure is linked to leukemia, and limited evidence suggests genotoxicity in workers.

Purpose of the Study:

• To assess the carcinogenic and genotoxic potential of 1,3-butadiene in humans based on available data.
• To estimate the potency of 1,3-butadiene for inducing cancer and reproductive effects.
• To identify and address uncertainties, including species-specific metabolic differences and genetic polymorphisms.

Main Methods:

• Review of epidemiological investigations and toxicological bioassays in mice and rats.
• Analysis of studies on reproductive effects in female mice.
• Consideration of species differences in metabolism and human metabolic variability.

Main Results:

• 1,3-Butadiene is highly likely to be carcinogenic and likely to be genotoxic in humans.
• Mice exhibit greater sensitivity to 1,3-butadiene's effects than rats, likely due to metabolic differences.
• Cancer and ovarian effect potencies were estimated, incorporating conservative approaches due to metabolic uncertainties.

Conclusions:

• The weight of evidence indicates 1,3-butadiene poses significant health risks, including cancer and genotoxicity, to humans.
• Species differences in metabolism necessitate conservative potency estimates for human risk assessment.
• Further research may be needed to fully elucidate the impact of genetic polymorphism on individual susceptibility.