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DEVELOPMENT OF A TIER II ENDOCRINE DISRUPTOR TEST GUIDELINE FOR MULTI-GENERATIONAL EXPOSURES OF THE ESTUARINE FISH, SHEEPSHEAD MINNOW TO REPRODUCTIVE TOXICANTS
Impact/Purpose:
The objective of this research is to provide the Office of Science Coordination and Policy within the Office of Prevention, Pesticides and Toxic Substances with a transferable two-generation toxicity test guideline using the sheepshead minnow, Cyprinodon variegatus. The two-generation test method will be assessed to determine the value added to the identification of reproductive effects on fishes by multiple generation exposures to endocrine disrupting chemicals, as compared to current shorter duration test guidelines. Statistical models will also be examined to determine their utility to predict population-level effects from data gathered in two-generation exposures to reproductive toxicants.
Description:
The Agency's Endocrine Disruptor Screening Program (EDSP) developed a two-tiered screening approach for identifying and characterizing endocrine effects of pesticides, industrial substances and environmental contaminants. Tier II tests include development of transgenerational (two-generation) tests with various animal species. This research will involve a collaborative effort between the Gulf Ecology Division (GED) and the Mid-Continent Ecology Division (MED) of ORD to develop a two-generation test guideline with fresh and saltwater fishes (including species specific requirements). Previously, survival and reproductive impacts on fish have been measured from exposures lasting one generation or less (i.e., 28 day early life-stage guideline, 21 day reproductive test, and the fathead and sheepshead minnow life-cycle toxicity tests). During guideline development we will assess the capacity of the shorter assays to reliably detect adverse multi-generational effects caused by exposure to reproductive toxicants. Focused laboratory studies across multiple dose levels and fish generations will evaluate the sensitivity and reproducibility of survival, growth, reproductive and biochemical endpoints as well as histopathology changes. Testing approaches and endpoints identified as having the greatest potential to singularly or collectively indicate reproductive impairment will be incorporated in the two-generation test guideline and examined to identify additional benefits gained and at what additional cost. Although not planned as part of the actual guideline development, GED proposes to incorporate population models in the data analysis component to make full use of these valuable data. Modeling efforts may provide valuable estimates of population-level effects associated with exposure to reproductive toxicants.