Risk assessment, as defined by the National Academy of Sciences in 1983, is comprised by the following components: hazard identification, dose-response assessment, exposure assessment, and risk characterization. The U.S. Environmental Protection Agency (EPA) has developed risk assessment guidelines which follow the NAS format for Program Offices to follow in evaluating the potential adverse effects of environmental agents on humans. Guidelines have been published in the Federal Register on cancer, mutagenicity, developmental toxicity, chemical mixtures, and exposure. Proposed guidelines are expected to be published shortly on female and male reproductive toxicity.