ABSTRACT
Risk assessment provides a quantitative approach to toxicology and chemical carcinogenesis. Before the development of risk assessment methods, there was no established method to determine the probability of disease due to measured exposure levels. Carcinogen risk assessment begins with an evaluation of whether a chemical has been shown to cause increased rates of specific neoplasms in either humans or animals. For many known human carcinogens, studies of humans have included exposure information sufficient to determine the dose–response relationship. In most instances, human exposure information comes from industrial hygiene measures in the workplace. When cancer risk assessment was first developed, all carcinogens were believed to act as mutagens producing irreversible changes and acting at one or more steps in a sequence of events leading to neoplasia. Although humans have been exposed to many chemicals classified as carcinogens, usually adequate exposure information is lacking from epidemiology studies for use in dose-response development.
