Incorporating Hormesis in the Routine Testing of Hazards

The phenomenon of subtoxic stimulation of organism response is not uncommon in aquatic toxicology experi-ments. We describe the presence of hormesis in both growth and reproduction experiments in aquatic toxicol-ogy where these responses are observed in both animals and plants and at different trophic levels of an ecosystem. The implications of ignoring hormetic responses in the analysis of toxicity data are discussed. In particular, we note that speci®cation of models that explicitly cannot accommodate or remove potential effects of hormesis may lead to biased potency estimates. Further, the presence of hormesis has implications for the design of toxicology experiments, with the spacing of concentration test conditions being critical