An exposure:activity profiling method for interpreting high-throughput screening data for estrogenic activity--proof...

Area of Science:

• Environmental toxicology
• Endocrine disruption screening
• Computational toxicology

Background:

• High-throughput in vitro screening (HTS) assays are available for estrogen-related endpoints.
• Databases like EPA's ToxCast™ and the Tox21 consortium contain extensive chemical assay results.
• Activity measurements alone are insufficient for chemical prioritization without exposure context.

Purpose of the Study:

• To extend exposure:activity profiling by calculating EARs and REEAQs.
• To integrate human exposure estimates with in vitro assay data for endocrine activity.
• To develop a metric for prioritizing chemicals for further endocrine screening or testing.

Main Methods:

• Calculated exposure:activity ratios (EARs) using human exposure estimates and AC50 values.
• Utilized data from seven estrogenic assays within ToxCast™ and Tox21.
• Derived relative estrogenic exposure:activity quotients (REEAQs) by comparing chemical EARs to genistein (GEN).

Main Results:

• Developed a novel method combining exposure and activity data for chemical assessment.
• Demonstrated the utility of EARs and REEAQs in providing exposure context for HTS assay results.
• Identified substances with low EARs and REEAQs as potentially low priority for further endocrine evaluation.

Conclusions:

• EARs and REEAQs provide valuable metrics for chemical prioritization in endocrine disruption screening.
• Integrating exposure data with in vitro activity enhances the utility of HTS assay results.
• This approach aids decision-making by identifying chemicals that warrant reduced or increased scrutiny for endocrine activity.