Update of Potency Factors for Asbestos-Related Lung Cancer and Mesothelioma.

The most recent update of the U.S. Environmental Protection Agency (EPA) health assessment document for asbestos (Nicholson, 1986, referred to as “the EPA 1986 update”) is now 20 years old. That document contains estimates of “potency factors” for asbestos in causing lung cancer (KL's) and mesothelioma (KM's) derived by fitting mathematical models to data from studies of occupational cohorts. The present paper provides a parallel analysis that incorporates data from studies published since the EPA 1986 update. The EPA lung cancer model assumes that the relative risk varies linearly with cumulative exposure lagged 10 years. This implies that the relative risk remains constant after 10 years from last exposure. The EPA mesothelioma model predicts that the mortality rate from mesothelioma increases linearly with the intensity of exposure and, for a given intensity, increases indefinitely after exposure ceases, approximately as the square of time since first exposure lagged 10 years... [ABSTRACT FROM AUTHOR]