USING EPIDEMIOLOGY DATA TO TESTS HYPOTHESES ABOUT THE CARCINOGENICITY OF ASBESTOS

Much research indicates that the carcinogenicity of any particular occurrence of asbestos is a function of the sizes, shapes, mineral types and, perhaps, other characteristics of the fibers within. Thus, because asbestos toxicity is a function of multiple factors involving the properties of entire crystals, unlike most toxins, the toxicity of a particular occurrence cannot be determined simply by reducing the asbestos to its component molecules (to determine concentration). Moreover, to adequately assess asbestos-related cancer risk, it will be necessary to definitively identify the full set of characteristics that mediate toxicity and determine the quantitative manner by which each contributes to toxicity.

Epidemiology studies, human pathology studies, whole-animal mortality studies, and tissue/cellular studies all provide information useful for identifying and quantifying the asbestos characteristics that mediate toxicity and risk. However, each type of study suffers from unique limitations and the existing literature is further limited by inadequate characterization of the exposures contributing to the effects studied. Yet, not only must exposures be adequately characterized, but studies of asbestos exhibiting a sufficiently broad range of characteristics need to be compared to support identification of the specific asbestos characteristics that mediate risk. In this talk, I will review the types of studies and the attendant comparisons (e.g., hypothesis testing/modeling) required to adequately assess asbestos risk and summarize the status of the supporting meta-analysis of human epidemiology studies that coworkers and I have been conducting as part of this effort.