Performing Spatially and Temporally Explicit Ecological Exposure Assessments Involving Multiple Stressors

Abstract

Ecological risk assessments have traditionally focused on estimating risk associated with a receptor's exposure to chemical stressors in abiotic (soil, water, etc.) and biotic (tissues, prey items) media. However, a free-living receptor is also constantly challenged to avoid or minimize adverse effects associated with those physical (e.g., loss of habitat) and biological (e.g., lack of adequate food) stressors that are already a consistent and natural part of its everyday existence. All three stressors, as well as their relative spatial and temporal positions with respect to each other and the receptor, may interact in ways that alter a chemical stressor's relative contribution to a receptor's overall risk. Evidence suggests that better representations of a chemical stressor's true contribution to overall risk would result if spatial, temporal, and multiple stressor interactions were more routinely considered and quantified. However, examples of this occurring in typical ecological risk assessments are rare, due, in part, to a lack of practical and accessible procedures for this purpose. This article outlines a procedure to give ecological risk assessment practitioners greater access to spatial, temporal, and multistressor techniques, describes an implementable spreadsheet-based model for performing calculations associated with this procedure, and discusses the types of ecological, life history, and landscape information needed to parameterize this model.

Keywords:

• ecological risk
• spatially explicit
• multiple stressors
• population level.

ACKNOWLEDGMENTS

This article benefited from constructive comments from three anonymous reviewers. All views or opinions expressed in this article are those of the author and do not necessarily represent Oregon Department of Environmental Quality policy or guidance. No official endorsement is implied or is to be inferred.

Notes

^a The specific values shown in this table are used in the hypothetical scenarios described in the text of this article; they are species-specific, location-specific, and scenario-specific.

^a Values from Table 4-1 and Table 4-2, USEPA (1993).

^b Values from Table 4-3, USEPA (1993).

^c ME_i = GE_i × AE_i (cf., Table 4-7, USEPA 1993).

^d Values shown are for the hypothetical examples; other values may be used in actual practice.

^e Calculated using Equation 1.

^f Calculated using Equation 8.