Ecological risk assessment

Ecological risk assessment is a procedure for evaluating the likelihood that adverse ecological effects are occurring, or may occur, in ecosystems as a result of one or more human activities. These activities may include the alteration and destruction of wetlands and other habitats, the introduction of herbicides, pesticides, and other toxic materials into the environment , oil spills , or the cleanup of contaminated hazardous waste sites. Ecological risk assessments consider many aspects of an ecosystem , both the biotic plants and animals and the abiotic water, soils, and other elements. Ecosystems can be as small as a pond or stretch of a river or as large as thousands of square miles or lengthy coastlines in which communities exist.

Although closely related to human health risk assessment, ecological risk assessment is not only a newer discipline but also uses different procedures, terminology, and concepts. Both human health and ecological risk assessment provide frameworks for collecting information to define a risk and to help make risk management or regulatory decisions. But human health risk assessment follows four basic steps that were defined in a 1983 by the National Research Council : hazard assessment, dose response assessment, exposure assessment, and risk characterization. In contrast, ecological risk assessment relies on a Framework for Ecological Risk Assessment published by Environmental Protection Agency in 1992 as part of a long-term plan to develop ecological risk assessment guidelines. The Framework defines three steps: problem formulation, analysis, and risk characterization.

The problems that human health risk assessments seek to address are clearly defined: cancer , birth defects , mortality , and the like. But the problems that ecological risk assessments tries to understand and deal with are less straightforward. For instance, a major challenge ecological risk assessors face is distinguishing natural changes in an ecosystem from changes caused by human activities and defining what changes are unacceptable. As a result, the initial problem formulation step of an ecological risk assessment requires extensive discussions between risk assessors and risk managers to define "ecological significance," a key concept in ecological risk assessment. Because it is not immediately clear whether an ecological change is positive or negative—unlike cancer or birth defects, which are known to be adverse—judgments must be made early in the assessment about whether a change is significant and whether it will alter a socially valued ecological condition. For example, Lake Erie was declared "dead" in the 1960s as a result of phosphorous loadings from cities and farms. But, in fact, there were more fish in the lake after it was "dead" than before; however, these fish were carp, suckers, catfish, not the walleyed pike, yellow perch, and other fish that had made Lake Erie one of the highest valued freshwater sport fishing lakes in the United States. More recently, with pollution inputs greatly reduced, the lake has recovered much of its former productivity. Choosing one ecological condition over the other is a social value of the kind fundamental to ecological risk assessment problem formulation. Once judgments have been made about what values to protect, analysis can proceed to examine the "stressors" that ecosystems are exposed to and a characterization can be made of the "ecological effects" likely from such stressors.

Since 1989, EPA has held workshops on "ecological significance" and other technical issues pertaining to ecological risk assessment and has published the results of its workshops in a series of reports and case studies. In 1996, EPA proposed its first ecological risk assessment guidelines, with final guidelines published in May of 1998. Overall, the direction of ecological protection priorities has been away from earlier concerns with narrow goals (e.g., use of commercially valuable natural resources ) toward broader interest in protecting natural areas such as National Parks and Scenic Rivers for both present and future generations to enjoy.

[David Clarke ]

RESOURCES

BOOKS

Ecological Risk Assessment Issues Papers. Washington, D.C.: United States Environmental Protection Agency, Risk Assessment Forum, 1994.

Framework for Ecological Risk Assessment. Washington, D.C.: United States Environmental Protection Agency, Risk Assessment Forum, 1992.

Priorities for Ecological Protection: An Initial List and Discussion Document for EPA. Washington, D.C. United States Environmental Protection Agency, 1997.

PERIODICALS

Lackey, R. T. "The Future of Ecological Risk Assessment." Human and Ecological Risk Assessment, An International Journal 1, no. 4 (October 1995): 339-343.