Application of an integrated testing strategy to the U.S. EPA endocrine disruptor screening program.

New approaches to generating and evaluating toxicity data for chemicals are needed to cope with the ever-increasing demands of new programs. One such approach involves the use of an integrated testing and evaluation strategy based on the specific properties and activities of a chemical. Such an integrated strategy, whether applied to existing or future programs, can promote efficient use of resources and save animals. We demonstrate the utility of such a strategy by applying it to the current U.S. Environmental Protection Agency Endocrine Disruptor Screening Program (EDSP). Launched in October 2009, the EDSP utilizes a two-tiered approach, whereby each tier requires a battery of animal-intensive and expensive tests. Tier 1 consists of five in vitro and six in vivo assays that are intended to determine a chemical's potential to interact with the estrogen (E), androgen (A), or thyroid (T) hormone pathways. Tier 2 is proposed to consist of multigenerational reproductive and developmental toxicity tests in several species and is intended to determine whether a chemical can cause adverse effects resulting from E, A, or T modulation. In contrast to the existing EDSP structure, we show, using the pesticide atrazine as an example, that a multilevel testing framework combined with an integrated evaluation process would significantly increase efficiency by minimizing testing.