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ENDANGERED AQUATIC VERTEBRATES: COMPARATIVE AND PROBABILISTIC-BASED TOXICOLOGY
Citation:
MAYER, F. L., D. R. BUCKLER, F. J. DWYER, M. R. ELLERSIECK, L. C. SAPPINGTON, J. M. BESSER, AND C. M. BRIDGES. ENDANGERED AQUATIC VERTEBRATES: COMPARATIVE AND PROBABILISTIC-BASED TOXICOLOGY. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/045, 2008.
Impact/Purpose:
To determine: 1) if listed aquatic vertebrate species are more sensitive to chemicals than non-listed species; 2) if common surrogate test species represent listed species toxicologically; and 3) if predictive acute and chronic models can be applied to hazard assessments with listed species where direct toxicity testing is not prudent or impractical.
Description:
It has previously been assumed that endangered, threatened, and candidate endangered species (collectively known as “listed” species) are uniquely sensitive to chemicals. The purpose of this cooperative research effort (U.S. Environmental Protection Agency, U.S. Geological Survey, U.S. Fish and Wildlife Service, University of Missouri) was to determine: 1) if listed aquatic vertebrate species are more sensitive to chemicals than non-listed species; 2) if common surrogate test species represent listed species toxicologically; and 3) if predictive acute and chronic models can be applied to hazard assessments with listed species where direct toxicity testing is not prudent or impractical. Toxicity tests were conducted with 29 species of fishes and amphibians and five chemicals (carbaryl, copper, 4-nonylphenol, pentachlorophenol, and permethrin) representing a broad range of toxic modes of action. For acute toxicity, rainbow trout (Oncorhynchus mykiss), the most sensitive surrogate species, was equal to or more sensitive than listed and related species 80% of the time. Only 3% of the species were significantly (P≤ 0.05) more sensitive than rainbow trout, and even then, the differences were within or very close to a factor of two (normal intra- and interlaboratory variation = 2-5x). Chronic toxicity tests with copper and pentachlorophenol indicated no significant greater sensitivity between rainbow trout and the listed species, spotfin chub (Cyprinella monacha) and fountain darter (Etheostoma fonticola). Using ICE for estimating acute toxicity, 100% of the values for listed or related species were within or very close to a factor of two of the observed values (n = 70, mean = 1.06, range = 0.49 - 2.24). ACE-estimated chronic toxicity values were within a factor of two of observed values 80-90% of the time and 100% within a factor of three. Species sensitivity distributions (SSD) were also developed to determine the 5th percentile effect among observed data and different sets of estimated data. The most accurate estimated acute toxicity SSDs were in using the surrogate species having the best correlation model in ICE (SSD = 0.95x observed SSD; range = 0.88 - 0.98). SSDs for chronic toxicity were also quite good with ACE-estimated chronic data or ICE-estimated acute data/acute-chronic ratio. 5th percentile estimates averaged 0.95 times those for observed data (range = 0.46 - 1.28). The results suggest that listed species are not universally more sensitive to contaminant exposure than other species on a toxicological basis. Surrogate test species do represent listed species toxicologically, and toxicities and hazard assessments (SSD) can be estimated accurately and precisely, not only for listed species, but other species as well.