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1,3-BUTADIENE
CAS No.: 106-99-0
I. PHYSICAL AND CHEMICAL PROPERTIES (from HSDB, 1998)
Molecular weight 54.09
Boiling point
-4.4° C
Melting point
-108.9° C
Vapor pressure
910 mm Hg at 20° C
Air concentration conversion 1 ppm = 2.21 mg/m 3 at 25° C
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor: 1.7 E-4 (µg/m 3 ) -1
Slope Factor: 6.0 E-1 (mg/kg-day) -1
[Calculated from lung alveolar and bronchiolar neoplasms in female mice (Melnick et al., 1990)
using a linearized multistage procedure (OEHHA, 1992).]
III.
CARCINOGENIC EFFECTS
Human Studies
Several studies have examined cancer mortality rates among industrial workers who were likely to have
been exposed to butadiene. However, these studies generally considered workers likely to have had
contemporaneous exposure to other potential carcinogens (most notable styrene). Nevertheless, studies
of two work environments are sufficiently specific to butadiene exposure to provide limited supporting
evidence for the carcinogenic effects observed in animal bioassays. These studies are a case-control
study of rubber workers by Matanoski et al. (1989) and cohort studies of a butadiene manufacturing
plant by Downs et al. (1987) and Divine (1990). In addition, Checkoway and Williams (1982)
observed statistical associations of blood abnormalities with butadiene exposure at a facility where
excess leukemia and lymphoma had been reported.
The first epidemiological study evaluating the possibility of an increased risk of carcinogenicity following
occupational exposure to butadiene and other compounds was conducted by the National Institute of
Occupational Safety and Health (NIOSH). A study conducted at the University of North Carolina
(Spirtas, 1976) prompted NIOSH to examine the issue of styrene-butadiene exposures and a possible
link to leukemia (NIOSH, 1976). Leukemia rates in the area surrounding the Port Neches plants,
Texas, were found to be above national rates.
McMichael et al. (1976) examined deaths occurring from 1964 through 1973 in a male population
which had been employed at a large tire manufacturing plant in Akron, Ohio. Standardized Mortality
Ratios (SMRs) for the study population indicated that deaths due to several types of cancer exceed
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