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Toxicity estimation using the ICE and ACE modeling tools

Project Purpose:
Develop web-based predictive modeling tools to assess the acute and chronic toxicity of chemicals to aquatic organisms and wildlife.

Project Description(s):
Two method and software products were developed to aid in estimating the toxicity of chemicals to species with limited or no data, including threatened and endangered species (T&E). Interspecies Correlation Estimation (ICE) models were developed to predict acute toxicity of a species from a surrogate species using Model II least squares regression, where both variables are independent and subject to measurement error (log X2 = a + b[log X1]). Acute to Chronic Estimation (ACE) was developed to predict no-effect and low-effect concentrations for chronic mortality from raw acute toxicity data using accelerated life testing and linear regression analysis. Currently ORD is developing internet versions of ICE and ACE for use by the Office of Pollution Prevention and Toxic Substances (OPPT and OPP). The development Web-ICE and Web-ACE research includes: (1) expansion of ICE models to wildlife and additional aquatic species and chemicals, (2) rigorous QA/QC and bootstrap validation, (3) inclusion of mode of action (MOA), chemical class, and taxonomic distance, and (4) multiple publications in peer reviewed journals. Bootstrap validation of ICE models for wildlife species found that for all models, ICE predicted within 5-fold of actual values for 85% of all bootstrap replicates and within 10-fold of actual values for 95% of all bootstrap replicates. ICE currently contains 500 toxicity values for 72 pharmaceutical compounds in 94 species.

Project Outcomes:
The ICE/ACE modeling approaches contribute to the ability to predict the effects of chemicals on aquatic and wildlife species, an essential component of the conceptual model for ecological risk assessment. Specifically, this approach facilitates the estimation of potential hazard for untested chemicals or chemicals with limited toxic effects information. Web-based versions of ICE and ACE will provide immediate action to updates and improvements, and allow greater user flexibility in searching and correlation analysis. Currently ICE is used by the Office Water in Biological Evaluations to ensure the protectiveness of national criteria to T&E species. Several technology transfer efforts have put ICE and ACE in the hands of Program Offices and the ecological risk community towards informing assessments in North America and Europe.

Mace Barron at barron.mace@epa.gov

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