| Using Metal-Ligand Binding Characteristics
to Predict Metal Toxicity: Quantitative Ion Character-Activity Relationships (QICARs) Michael C. Newman,1 John T. McCloskey,2 and Christopher P. Tatara3 1College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, Virginia;
2U.S. Fish and Wildlife Service, Gloucester, Virginia;
3University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina Abstract
Ecological risk assessment can be enhanced with predictive models for metal toxicity. Modelings of published data were done under the simplifying assumption that intermetal trends in toxicity reflect relative metal-ligand complex stabilities. This idea has been invoked successfully since 1904 but has yet to be applied widely in quantitative ecotoxicology. Intermetal trends in toxicity were successfully modeled with ion characteristics reflecting metal binding to ligands for a wide range of effects. Most models were useful for predictive purposes based on an F-ratio criterion and cross-validation, but anomalous predictions did occur if speciation was ignored. In general, models for metals with the same valence (i.e., divalent metals) were better than those combining mono-, di-, and trivalent metals. The softness parameter ( p) and the absolute value of the log of the first hydrolysis constant (|log KOH|) were especially useful in model construction. Also,  Eo contributed substantially to several of the two-variable models. In contrast, quantitative attempts to predict metal interactions in binary mixtures based on metal-ligand complex stabilities were not successful. -- Environ Health Perspect 106(Suppl 6) :1419-1425 (1998) . http://ehpnet1.niehs.nih.gov/docs/1998/Suppl-6/1419-1425newman/abstract.html Key words: metal, toxicity, prediction, model, ion characteristics
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