United States Environmental Protection Agency (USEPA) framework for ecological risk assessment

Significance: These documents, prepared by USEPA Risk Assessment Forum,

constitute USEPA's general framework for conducting ecological risk

assessments. They provide the broad outlines and general terminology for

ecological risk assessment. Most Federal and state guidances borrow from this

framework in varying degrees. This subsection summarizes the most recent

framework document (USEPA Risk Assessment Forum 1996c) because it

includes the principles of the earlier framework document (USEPA Risk

Assessment Forum 1992d) and provides the generally accepted state of the

practice in terms of the broad goals and methods which an ecological risk

assessment should address and apply. This document and associated supporting

material provide the basic definitions and processes which comprise the

foundation for most Federal, state, and industry sponsored guidance. This

summary addresses the questions:

a. What are the major elements, basic definitions, and processes described in

this framework?

b. How is the framework being incorporated into current guidance?

c. How is the framework being incorporated in current practice?

e.g. Solomon et al. (1996) assessed risk to surface waters from atrazine.

Both studies follow the USEPA three-component model using Problem

Formulation, Analysis, and Risk Characterization.

d. What elements of the framework are most adaptable to dredged material

disposal problems?

Definitions: This subsection is not a comprehensive risk assessment glossary

but provides some fundamental definitions necessary for an informed reading of

the framework document and the various guidance documents which follow it.

a. Assessment end point: An explicit expression of the environmental value

that is to be protected. An assessment end point includes both an

ecological entity and specific attributes of that entity. For example,

salmon are a valued ecological entity; reproduction and population

maintenance of salmon form an assessment end point.

b. Conceptual model: The conceptual model describes a series of working

hypotheses of how the stressor might effect ecological entities. The

conceptual model also describes the ecosystem potentially at risk, the

relationship between measures of effect and assessment end points, and

exposure scenarios.

c. Ecological risk assessment: The process that evaluates the likelihood that

adverse ecological effects may occur or are occurring as a result of

exposure to one or more stressors.

d. Exposure: The contact or co-occurrence of a stressor with a receptor.

e. Hazard assessment: This term has been used to mean either

(1) evaluating the intrinsic effects of a stressor or (2) defining a margin or

Appendix A Summary of Federal, State, and Regional Guidance