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On August 25-27, 2009, the FIFRA Science Advisory Panel (SAP) will review the “Use of Structure Activity Relationships of Estrogen Binding Affinity to Support Prioritization of Pesticide Inert Ingredients and Antimicrobial Pesticides for Screening and Testing.”

The use of structure-activity relationships (SARs) in early hazard identification is a cost-effective prioritization tool that can guide the systematic collection of key test data.  EPA has asked the SAP to review a new SAR approach that was developed for pesticide inert ingredients and antimicrobial pesticides to help prioritize candidate chemicals for the Tier 1 Endocrine Disruptor Screening Program. The Agency is required to screen all pesticide chemicals including active ingredients and other (“inert”) ingredients, for endocrine disruption potential. 

To satisfy the requirement, the Agency must first prioritize hundreds of chemicals for endocrine disruption screening and testing in biologically complex and resource-intensive assays.   A particularly challenging issue is the development of prioritization techniques for chemicals that have minimal existing toxicological information.

The SAP will be asked to comment on various aspects of this SAR approach, including transparency of the approach, definition of the biological endpoint, mechanistic interpretation, and the applicability of the model for certain chemicals. In its 1998 report (PDF) (92 pp, 600k, About PDF) the Endocrine Distruptor Screening and Testing Advisory Committee envisioned that "when it comes time to set priorities for the first phase of tier 1 screening, HTPS data (as well as improved QSARs) should be used along with other relevant exposure and effects data." This new SAR approach for predicting estrogen receptor binding affinity is based on data derived from two in vitro assays: one optimized to measure the potential of chemicals to bind rainbow trout estrogen receptors, and a second that measures gene activation through production of vitellogenin.

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