September 1992 CIIT scientists recently reported evidence that suggests that human exposure to 1,3-butadiene, one of the 189 hazardous air pollutants identified in the Clean Air Amendments, may pose less of a cancer risk than originally believed.
Different species react to chemical exposure in different ways.
Butadiene, a compound widely used in the production of synthetic rubber and other resins, causes cancer in many organs in both rats and mice, but mice are about 1000 times more sensitive to its carcinogenic effects than rats. The cancer-causing effects of butadiene are thought to result from the conversion of butadiene in the body to one or more toxic metabolites, primarily butadiene monoepoxide. This metabolite is believed to react with DNA, the genetic material in cells, to begin the carcinogenic process. Therefore, CIIT scientists compared the rates at which the liver tissues from humans, rats, and mice metabolize butadiene to butadiene monoepoxide, as well as the rates at which each species detoxified the metabolite. These comparisons provided clues as to the differences among humans, mice, and rats in the capability of butadiene to initiate cancer by producing the monoepoxide.