The potential usefulness of biological markers in risk assessment.

Substantial data have been generated during the last 5 years in experimental systems and human populations which shed light on the potential usefulness of biological markers in human cancer risk assessment. Following a brief review of overall progress to date in the biomonitoring of human populations, this paper turns to the growing body of data regarding carcinogen-DNA and protein adducts as illustrative markers of biologically effective dose of carcinogens. The data base illustrates considerable human inter-individual variation in binding and the presence of significant "background" levels of adducts--both of which support the absence of human population thresholds for exposure to carcinogens. The contribution of adduct data to our understanding of the shape of low dose-response curve and the reliability of inter-species extrapolation, as well as the relevance of adducts to cancer risk, are also discussed. Even though adducts can now be useful in hazard identification or qualitative risk assessment, more research is needed before they can serve as quantitative predictors of human cancer risk.