Abstract
FDA's efforts during the early 1970s to establish acceptable food exposure levels for carcinogenic animal drugs such as diethylstilbestrol (DES) led the agency to incorporate quantitative risk assessment into its decision-making process. During the nearly two decades since FDA first introduced risk assessment as a regulatory tool, its uses have been expanded to almost all areas of chemical regulation. The major driving forces behind this expansion have been (1) the need to deal systematically with the large number of commercially important chemicals that have been identified as animal carcinogens and that have been found to occur widely in the environment and (2) the large number of laws that now require regulatory agencies to establish limits on human exposure to these substances.