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

safety or quotient by comparing a toxicological effects concentration with

an exposure estimate.

f. Measure of effect: A measurable ecological characteristic that is related

to the valued characteristic chosen as the assessment end point.

g. Measure of exposure: A measurable stressor characteristic that is used to

help quantify exposure.

h. Receptor: The ecological entity exposed to the stressor.

i. Risk characterization: A phase of ecological risk assessment that

integrates the exposure and stressor response profiles to evaluate the

likelihood of adverse ecological effects associated with exposure to a

stressor. The adversity of effects is discussed, including consideration of

the nature and intensity of the effects, the spatial and temporal scales, and

the potential for recovery.

j. Stressor: Any physical, chemical, or biological entity that can induce an

adverse response (synonymous with agent).

k. Stressor-response profile: The product of characterization of ecological

effects in the analysis phase of ecological risk assessment. The stressor-

response profile summarizes the data on the effects of a stressor and the

relationship of the data to the assessment end point.

Summary: "Proposed guidelines for ecological risk assessment" expands

upon the earlier EPA framework document, "Framework for ecological risk

assessment." Appendix A of the proposed guidelines indicates specific changes

that were made from the framework of the EPA's ecological risk assessment. The

purpose of an ecological risk assessment, according to this document, is to

"organize and analyze data, information, assumptions, and uncertainties in order

to evaluate the likelihood of adverse ecological effects." It describes four elements

of an ecological risk assessment: planning stage, problem formulation phase,

analysis phase, and the risk characterization phase.

The authors of the document also emphasize that an ecological risk assessment

is an "iterative" process in which reevaluation and revision is important in each

phase.

a. Planning stage. Before beginning the risk assessment, a planning stage, in

which there is dialogue between the risk assessor, risk manager, and other

parties, should be implemented. The purpose of this planning stage is to

ensure that the risk assessment results meet the needs of the risk manager,

who is responsible for protecting human health and the environment. In

this planning stage, the management goals, scope and complexity,

resources needed, and products of the assessment should be discussed and

summarized. The document mentions that significant planning is required

for a project in which the risk assessment is for a watershed where there

are multiple stressors, ecological values, and political factors influencing

Appendix A Summary of Federal, State, and Regional Guidance