Some issues in the quantitative modeling portion of cancer risk assessment.

Abstract Several questions should be asked in order to determine the relevance and scientific merit of a quantitative cancer risk assessment. Twenty such questions are formulated here and briefly discussed. These questions are intended to identify important issues and serve as a checklist for risk managers and developers of quantitative risk assessments. Among the many factors involved in these questions are the carcinogenic response, quantal response models, time to response, competing risks, model shapes, goodness of fit, dose scale, high-to-low-dose extrapolation, consistency across different subjects, animal-to-human extrapolation, route-to-route extrapolation, exposure durations and patterns, short-term tests, consistency with human epidemiological data, human exposures, statistical variability, impacts of assumptions and policy decisions and value judgments, risk characterization, upper and lower bounds, and keeping pace with scientific advances.