Butadiene is an important intermediate in the production of synthetic rubber but causes cancer in the B6C3F1 strain of laboratory mouse, an animal widely used to assess the risk of chemicals. Tumours have also been found in rats although the dose was very high.
Based on the experiments with B6C3F1 mice, America's National Institute of Occupational Safety and Health (NIOSH) has classified butadiene as a carcinogen, estimating that exposure to 2 parts per million for 45 years would result in 597 cancers per 10,000 people. However, careful observation of butadiene plant workers employed since 1945, and exposed to much higher levels of the chemical, revealed no extra cancers. On the contrary, overall cancer deaths were considerably less than among the ordinary public.(1)
The NIOSH findings have been criticised since there are many differences between people and the cancer prone B6C3F1 mouse. According to an editorial in the journal Science ,(1) "with trillions of dollars, loss of competitiveness, and jobs at stake, a searching review of the risk assessment methodology of the regulatory agencies is overdue."
1) P.H.Abelson, Science, 1992, June 19, 1609.
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