Cancer risk assessment methodology for regulatory purposes is currently in a watershed time period, reflecting a new emphasis on more science-based risk assessment that takes into account research into mode of action and mechanisms of carcinogenesis. Under new EPA risk assessment guidelines, if sufficient data are available to support nonlinearity, a margin of exposure (MOE) approach based on a benchmark dose and uncertainty factors can be employed to assess risk, as has been done in the past only for noncancer endpoints. new cancer risk assessment methodologies of the U.S. Environmental Protection Agency on the risk for radiation-induced cancer, which do not assume linear dose-responses and for possible thresholds.

These methodologies are in direct conflict with the current LNTH models used for radiation and may alter our standards for radiation exposure.

Examine the potential impact of new cancer risk assessment methodologies of the U.S. Environmental Protection Agency on the risk for radiation-induced cancer.

Our group has developed the Carcinogenic Potency Database (CPDB), which analyzes 6000 animal cancer tests on 1460 chemicals. We will use the CPDB in the following work: (1) Rank human exposures to rodent carcinogens in workplace, air, food, water, and as pharmaceuticals, using a Margin of Exposure approach which indicates the margin of safety from the rodent carcinogenic dose for typical human exposures.
Our analysis will identify exposures that have a safety or uncertainty factor lower than 100-fold, for example, and will communicate how current practice compares to recommendations of the new EPA guidelines for benchmark dose. (2) Investigate the relationship between cancer potency (q1*) and the reference dose (RfD). This analysis will permit an assessment of the extent to which regulatory policy based on cancer would differ from policy based on other toxicological endpoints. (3) Investigate rodent bioassay results where test doses are at least 50 times below the maximum tolerated dose. We examine dose-response and the extent to which uncertainties about low-dose risk might be reduced by testing at lower doses and therefore reduce some of the boundedness of potency estimation.