The implications of hormesis to ecotoxicology and ecological risk assessment.

Changes required for the explicit recognition of hormesis are outlined for both ecotoxicology and ecological risk assessment (ERA). A major research need is the extension of hormesis beyond chemical stressors to abiotic (e.g., habitat) and biotic stressors (e.g., species introductions, organism interactions). An overreaching research need is to determine for all stressors with model organisms, populations, and communities whether hormesis has positive, neutral, or adverse effects. The latter are the least likely; however, neutral effects cannot be ruled out. Based on our present state of knowledge, hormesis is likely to have more of an impact on ecotoxicology than on ERA. In the case of the latter, it is most likely to make a difference only in a detailed-level ecological risk assessment (DLERA), the most complex form of ERA. Further, for hormesis to be accepted fully into ecotoxicology or ERA will require a paradigm shift. Three ongoing paradigm shifts to which hormesis could be linked are: recognition of the low utility of no-observed-effects concentrations (NOECs); recognition of the need for special treatment of essential element dose concentration responses, which are similar to hormesis; and the replacement of environmental toxicology with ecological toxicology (ecotoxicology).