Introduction

Ecological risk assessment for toxic chemicals has become an important part of the decision-making process for managing environmental problems (Suter 1993; U.S. EPA 1998). Risk assessments are used to evaluate environmental problems associated with past, ongoing, and potential future practices. For example, risks to plants, invertebrates, amphibians, reptiles, birds, and mammals are considered in the evaluation of chemical contamination at hazardous waste sites under the Superfund program administered by the U.S. Environmental Protection Agency (EPA) and under similar programs in most U.S. states, in Canada, in Europe, and in other countries throughout the world. In pesticide regulatory programs, ecological risk assessments are used to evaluate new chemicals as part of the registration process or new uses for already registered pesticides. Risk assessments also support environmental decisions about siting new facilities, about waste discharges, and about remedial actions to clean up or treat contaminated areas.