Cancer and non-cancer risk assessment should be harmonized

Although fundamentally different risk assessment procedures have traditionally been applied to carcinogens and non-carcinogens, this dual approach does not have strong scientific support. We believe that this dichotomy between cancer and non-cancer risk policies has led to severe imbalances in the cost of regulation and the level of protection afforded by various regulations. Moreover, the practice of providing quantitative estimates of human risk from animal data has blurred the distinction between what is known and what is not known concerning risk to human populations, which has in turn caused misunderstanding and misuse of risk assessment by regulators and the general public. Therefore, we advocate harmonization of risk assessment practices for cancer and non-cancer endpoints by use of a common default risk assessment procedure that does not routinely involve making quantitative estimates of low-dose human risks from animal data. During the past 20 years risks from exposure to carcinogens and noncarcinogens have been assessed using fundamentally different approaches. Quantitative estimates of carcinogenic risks have been obtained by extrapolation to low doses using a linear dose-response model. Acceptable exposures to non-carcinogens have been estimated by applying uncertainty factors to NOAELs (no-observed-adverse-effect levels). The practical outcome of this dual approach has been that chemicals determined to be carcinogenic, regardless of their mechanisms of action, have been regulated much more stringently than chemicals causing other types of toxicity.