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The term validation has appeared in the literature with great regularity in the last few years, but the process has yet to be explicitly stated. Most of the predictions of environmental hazard are based primarily, and sometimes entirely, on laboratory toxicity tests involving single species. While this may change over the years, it will remain true for the immediate future. Therefore, the validation process must start with an explicit statement of the types of predictions being made on the basis of single species laboratory toxicity tests. Unfortunately, the terms no-adverse-biological-effects concentration or biologically safe concentration, or no-observable-effects level might lead the unwary to believe that all possible adverse effects were unlikely to occur at concentrations below the one stated. In fact, I have never seen a body of evidence in a scholarly professional journal that would convince reviewers that these assertions had been confirmed in a scientifically sound way. Some more modest but more explicit predictions and validation criteria, for illustrative purposes only, follow. 1. Only the test species is expected to be protected fully in natural systems, and validation means confirming this assumption in the field. 2. Other species than the one(s) actually tested are thought to be protected at the no-observable-effects concentration, and a list of these species inhabiting the natural systems in question is included. Validation is carried out with field observations on all of these species. 3. No adverse effects at the community level of biological organization will occur, and the characteristics used to validate this assumption are listed. Validation may be carried out in microcosms or mesocosms under certain circumstances but should be based on field observations whenever possible. 4. No adverse effects will occur at the ecosystem level of organization, and the characteristics at the ecosystem level used to validate this assumption are listed. Validation in field enclosures or natural systems should probably be mandatory.
By coupling the explicit predictions being made with the explicit end points being used to validate these predictions, a more systematic and orderly process of validation will ensue. Until more hypothesis testing is carried out in the field of hazard evaluation than is in place presently, it is unlikely that the field will get the recognition it deserves.
ecotoxicology, toxicity testing, hazard evaluation, bioassays, field studies, validation
University Distinguished Professor, Department of Biology, and director, University Center for Environmental Studies, Virginia Polytechnic Institute and State University, Blacksburg, VA