2. Relevance to Public Health 2.1 Background and Environmental Exposures to 1,3-butadiene in the United States

1,3-Butadiene is a highly volatile gas that is used in the production of synthetic rubber; the major end use of the synthetic rubber is automobile tires. 1,3-Butadiene is also used for the production of high impact polystyrene and acrylonitrile-butadiene-styrene (ABS) resin plastics The predominant source of 1,3-butadiene in the atmosphere is industrial releases, which can occur during manufacturing, use, transport, and storage of the chemical. Automobile exhaust is a constant source of low levels of 1,3-butadiene release to the atmosphere. Minor sources of 1,3-butadiene in the atmosphere include cigarette smoke, wood burning (including forest fires), and the burning of rubber and plastics. In the atmosphere, 1,3-butadiene is expected to undergo photo-initiated destruction with a half-life of approximately 6 hours. Relatively low levels of 1,3-butadiene are released to water and soil. 1,3-Buta­ diene in water or soil is expected to rapidly evaporate to the atmosphere.