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Incorporating exposure information into the toxicological prioritization index decision support framework
Sumit Gangwal1, David M Reif, Shad Mosher
1National Center for Computational Toxicology (NCCT), Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA.
The Science of the Total Environment
|August 7, 2012
Summary
The Toxicological Prioritization Index (ToxPi) framework can integrate chemical exposure data for better hazard assessment. Incorporating exposure metrics refines chemical rankings, aiding toxicological prioritization for further testing.
Area of Science:
- Environmental toxicology
- Risk assessment
- Chemical safety
Background:
- The Toxicological Prioritization Index (ToxPi) is a decision support framework for prioritizing chemicals based on hazard data.
- Previous applications of ToxPi focused on bioprofiling data for hazard assessment, such as endocrine disruption potential.
- Integrating exposure information is crucial for effective chemical prioritization alongside hazard data.
Purpose of the Study:
- To demonstrate the utility of the ToxPi framework in incorporating chemical exposure information.
- To rank chemicals using exposure surrogates and investigate their relationship with higher-tiered exposure estimates.
- To improve the understanding of key exposure metrics and their influence on chemical prioritization.
Main Methods:
- Applied the ToxPi tool to common exposure surrogates including fate parameters, manufacturing volume, and occurrence measurements.
- Investigated the relationship between chemical rankings derived from exposure surrogates and higher-tiered exposure estimates.
- Analyzed how the incorporation of human exposure potential data alters chemical rankings.
Main Results:
- The relative ranking of chemicals changes as more direct human exposure potential information is integrated into the ToxPi framework.
- ToxPi results, when binned, align with chemical priorities based on basic population-level exposure measures for a subset of chemicals.
- However, these bins do not accurately predict higher-tiered exposure estimates, such as those used in pesticide registration.
Conclusions:
- The ToxPi framework provides insights into factors driving chemical rankings and aids in identifying critical exposure metrics.
- While ToxPi can incorporate exposure surrogates, additional exposure data is necessary to enhance confidence in exposure-based chemical prioritization.
- The study highlights the challenges in assessing the relevance of exposure surrogate tools for chemical prioritization.
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