The Toxic Substances Control Act (TSCA) is the legislation used by the U.S. Environmental Protection Agency to regulate releases of genetically engineered microorganisms. The rule defining the scope of the notification requirements for releases of microbial products of biotechnology was published in April 1997. The Environmental Protection Agency (EPA) had some latitude regarding the extent to which various categories of microorganisms would be regulated, but the agency was constrained by requirements of TSCA and an interagency agreement about how to regulate products of biotechnology. This paper investigates the extent to which the scope of oversight is based on risk. A risk-based rule is defined as one where the reporting requirements are based on potential for exposure or expected adverse effects. The evolution of the rule is described, and risk-based components are discussed. In conclusion, the scope of oversight of microbial releases is determined to be based on risk to the extent that legislation and institutional constraints permit.
