US EPA

This risk assessment of 1,3-butadiene, a gas used commercially in the production of various resins and plastics, concludes that 1,3-butadiene is a known human carcinogen, based on three types of evidence: 1) excess leukemias in workers occupationally exposed to 1,3-butadiene (by inhalation), 2) occurrence of a variety of tumors in mice and rats by inhalation, and 3) evidence in animals and humans that 1,3-butadiene is metabolized into genotoxic metabolites.

The best estimate of human lifetime extra cancer risk from chronic exposure to 1,3-butadiene is 9 X 10-3 per ppm based on a linear extrapolation of the increased leukemia risks observed in occupationally exposed workers. The corresponding estimate of the chronic exposure level of 1,3-butadiene resulting in an extra cancer risk of 10-6 (i.e., one in a million) is 0.1 ppb.

1,3-Butadiene also causes a variety of reproductive and developmental effects in mice and rats; no human data on these effects are available. There are insufficient data from which to draw any conclusions on potentially sensitive subpopulations.

Koppikar, A. Health Assessment Document for 1,3-Butadiene (External Review Draft). U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Washington Office, Washington, DC, NCEA-W-0267, 1998.

Send comments to butadiene@epamail.epa.gov.
Comment period has been extended from 4/10/98 to 4/17/98.