Scale dependency in the ecological risks posed by pollutants: is there a role for ecological theory in risk assessment?

Abstract

This chapter attempts to shed light on an area of tension in ecotoxicological risk assessment; the trade-off between experimental control in laboratory toxicology and the realism of field-based measurement. This trade-off is brought most sharply into focus through the issue of extrapolation of risk estimates between the laboratory and the field. It is a paradigm of ecotoxicology that it is possible to build tiers of test procedures, rooted in highly controlled, often elaborate, laboratory-based test systems from which we can make forecasts of potential harm to organisms in the polluted environment. These predictions then form the basis for regulatory decisions concerning pollutant release and control. This paradigm became established through the unification of toxicology (because of the need to understand the relationship between dose and effect) and environmental chemistry (because of the need to determine environmental concentration and hence, potential exposure). The massive inputs of science and technology involved in this process have been fuelled and motivated by the need for regulation, legislation and the setting of environmental quality standards. The output from risk assessment procedures fulfils the need in these formalized systems, for repeatability, reliability and low cost. This chapter examines whether or not the paradigm of extrapolating risks between the laboratory and the field has been rigorously challenged, and explores some of the alternative criteria that ecotoxicologists with a more ecological perspective might select. It argues that a truly unified and scientifically defendable approach to risk assessment can only be achieved if the third conceptual arm of ecology is added to toxicology and environmental chemistry