Environmental Protection Agency.
Notice of Availability.
This notice announces the availability of a final report titled, Health Assessment of 1,3-Butadiene (EPA/600/P-98/001F), which was prepared by the U.S. Environmental Protection Agency's (EPA) National Center for Environmental Assessment (NCEA) of the Office of Research and Development (ORD).
This document will be available on or about October 30, 2002.
The document will be made available electronically through the NCEA Web site (http://www.epa.gov/ncea). A limited number of paper copies will be available from the EPA's National Service Center for Environmental Publications (NSCEP), P.O. Box 42419, Cincinnati, OH 45242; telephone: 1-800-490-9198 or 513-489-8190; facsimile: 513-489-8695. Please provide your name, your mailing address, the title and the EPA number of the requested publication.Start Further Info Start Printed Page 66152
FOR FURTHER INFORMATION CONTACT:
The Technical Information Staff, National Center for Environmental Assessment/Washington Office (8623D), U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue, NW., Washington, DC 20460. Telephone: 202-564-3261; fax: 202-565-0050; e-mail: firstname.lastname@example.org.End Further Info End Preamble Start Supplemental Information
This assessment was conducted to review the new information that has become available since EPA's 1985 health assessment of 1,3-butadiene.
1,3-Butadiene is a gas used commercially in the production of styrene-butadiene rubber, plastics, and thermoplastic resins. The major environmental source of 1,3-butadiene is the incomplete combustion of fuels from mobile sources (e.g., automobile exhaust). Tobacco smoke can be a significant source of 1,3-butadiene in indoor air.
This assessment concludes that 1,3-butadiene is carcinogenic to humans by inhalation, based on the total weight of evidence. The specific mechanisms of 1,3-butadiene-induced carcinogenesis are unknown, however, it is virtually certain that the carcinogenic effects are mediated by genotoxic metabolites of 1,3-butadiene.
Animal data suggest that females may be more sensitive than males for cancer effects; nevertheless, there are insufficient data from which to draw any conclusions on potentially sensitive subpopulations.
The human incremental lifetime unit cancer (incidence) risk estimate is based on extrapolation from leukemias observed in an occupational epidemiologic study. A twofold adjustment to the epidemiologic-based unit cancer risk is then applied to reflect evidence from the rodent bioassays suggesting that the epidemiologic-based estimate may underestimate total cancer risk from 1,3-butadiene exposure in the general population.
1,3-Butadiene also causes a variety of reproductive and developmental effects in mice; no human data on these effects are available. The most sensitive effect was ovarian atrophy observed in a lifetime bioassay of female mice. Based on this critical effect and using the benchmark concentration methodology, an RfC (i.e., a chronic exposure level presumed to be “without appreciable risk” for noncancer effects) was calculated.Start Signature
Dated: October 23, 2002.
Assistant Administrator, Office of Research and Development.
[FR Doc. 02-27625 Filed 10-29-02; 8:45 am]
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