Risk assessment of carcinogenic and noncarcinogenic chemicals.

"Risk Assessment" is a general term used with increasing frequency by both scientists and regulators. Scientifically based risk assessments consider available toxicologic data when judging which agents pose a significant risk to the human population. The science of toxicology focuses on identifying potential hazards to human health using surrogate animal studies. Margins of Safety and establishment of ADIs (Acceptable Daily Intakes) are methods applied to animal test data to set "safe" levels of potential exposure. While the use of Safety Factors in development of the ADI can support a pragmatic conclusion of safety, this approach cannot provide estimates of the probability of harm or the degree of safety. Therefore, Quantitative Risk Assessment (QRA) methods using mathematical models have been advanced to extrapolate from animal exposures which are usually high to much lower human exposure levels where experimental response is absent. Such methodology has been applied primarily by U.S. regulatory agencies to experimental oncogenic responses to estimate the risks of chemical exposure. The present manuscript considers both methods for evaluation of chemical safety and focuses on the scientific merits and limitations of each.