Lam, J. and S.Z. Cohen. November, 2006.
Prediction of Pesticide Toxicity to Amphibians: Testing a Preliminary Screening Equation and EPA's 'ICE' Equations with New Data, poster presented at SETAC (Society of Environmental Toxicology and Chemistry) North America 27th Annual Meeting, Montreal, Quebec, Canada, November 5-9, 2006.
There is a general consensus that amphibian populations are declining globally, and concern of an increase in the rates of malformations. Many possible causes have been suggested for these declines including: changes in predation and/or habitat, endoparasite infestation and disease (chytridiomycosis), ultraviolet radiation, mineral depletion, and natural or man-made chemicals, including pesticides. Extensive pre-registration testing of pesticides for environmental risks does not include amphibians, but does usually include cold water fish species. To help satisfy this data gap for ecological risk assessments, we previously proposed a two-step, simple equation to predict amphibian toxicity from more readily available rainbow trout data (Reid, et al., 2000). The equation uses acute toxicity data to predict MACs that would protect amphibians from acute, delayed toxic, and chronic effects. It involves a regression equation that uses rainbow trout LC50 data to predict western chorus frog LC50, and from that an MAC is derived for amphibians by multiplying the latter value by 0.03. At the time, minimal data were available to test the equation. Earlier work indicated that trout and amphibians both appear to have a mixed-function oxidase detoxification system less active than in mammals. We now use more recent data to evaluate the extent to which the equation predicts an MAC that is protective of amphibians for toxic effects. We are currently evaluating 58 combinations of pesticides, species, and toxic endpoints. This includes 12 pesticides, 10 species, and 15 endpoints. To date, the equation has only lacked adequate conservatism for the only two organometallic pesticides in the data set (mancozeb and triphenyltin) plus the herbicide endosulfan. The use context of this equation has been amphibian risk assessment at the watershed scale for proposed golf course and housing developments. It may be useful for future national pesticide regulatory risk assessments.