An interspecies correlation estimation (ICE) model to predict acute toxicity of organic chemicals to the African clawed frog (Xenopus laevis) using rainbow trout (Oncorhynchus mykiss) data.

An interspecies correlation estimation (ICE) model is presented to predict the 96-h acute LC50 for tadpoles of the African clawed frog (Xenopus laevis) using juvenile rainbow trout (Oncorhynchus mykiss) 96-h LC50 values. Both species are standard laboratory test species with a long history in aquatic toxicology. While the rainbow trout is one of the fish species most commonly used for acute testing, the African clawed frog is primarily used in endocrine assays. However, acute toxicity information for X. laevis may be required for test concentration setting in the endocrine assays and, where required, as input for the aquatic risk assessment for amphibians. To establish the correlation equation, acute toxicity data were collected for X. laevis and matched with those for O. mykiss from publicly available databases. After curating the data (i.e., converting the units, calculating geometric mean values in case multiple values for a chemical were available, and checking for potential outliers), the regression equation was established based on 138 LC50 values for 69 chemicals. As expected, there was a highly significant correlation between the two species (Spearman's rs = 0.86, p < 0.0001) and the ICE was deemed statistically robust (R² = 0.74; p < 0.0001) according to the criteria of US EPA's software WebICE. The obtained regression equation can be used as a non-testing method to generate an amphibian LC50 value (in case a rainbow trout value is available) for use in hazard and risk assessment. By applying this robust ICE model, additional vertebrate studies can be avoided.