Competing Issues in Contaminated Site Risk Assessment: A Case Study. S. M. Hoover, Golder Associates Ltd., 500-4260 Still Creek Drive, Burnaby, B.C. Canada V5C6C6; and R. A. Hill, Triton Environmental Consultants Ltd., 120-13511 Commerce Parkway, Richmond, B.C. Canada V6V 2L1
Many authors have emphasized the importance of considering population-level effects in ecological risk assessments at contaminated sites. However, risk assessors are typically faced with limited time and money, a large number of contaminants and potential exposure pathways, and an inadequate database on effects endpoints. Given this situation, a simplified approach is often taken where estimated exposure levels are compared to a toxicity reference value. Toxicity reference values are derived from studies that estimate either a no observed adverse effect level (NOAEL) or lowest observed adverse effect level (LOAEL). The common aspect of such studies is their focus on individuals and the proportion of individuals in a study that are affected. As noted above, however, ecological effects are generally of concern at the level of populations and communities rather than at the level of the individual. In this paper, we use a case study from northern Canada to illustrate the practical difficulties of conducting an ecological risk assessment and some of the resulting shortcomings. We discuss the competing issues faced by the risk assessor in carrying out the assessment and review the additional steps that could be taken to extend these assessments to more ecologically meaningful measures.
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