EDSP Screens and Tests for List 1

C. Holmes, P. Kwiatkowski, EM Mihaich
EPA’s Endocrine Disruptor Screening Program (EDSP) was initiated in 2009 -2010 with the issuance of test orders requiring manufacturers and registrants of 57 pesticide active ingredients and 9 pesticide inert/high production volume chemicals to evaluate the potential for these chemicals to interact with the estrogen, androgen and thyroid hormone systems. The EPA Tier 1 endocrine screening battery (ESB) consists of 11 distinct assays comprising both in vitro and in vivo test systems.

Much effort has gone into developing and standardizing these screens. However, there are still challenges in utilizing the results to identify a substance’s potential to interact with the endocrine system of humans and wildlife as some of the ESB
methods lack specificity for differentiating potential endocrine mediated responses from responses via other modes of action or via general toxicity. In addition, screening of compounds
using the ESB is not a trivial undertaking as the ESB can take many years to complete and costs $750,000 to $1,000,000 per chemical. The Tier 1 testing battery is intended to be evaluated in its entirety in a weight-of–evidence approach to determine whether or not a test chemical potentially interacts with the
endocrine system. If results from the Tier 1 battery are considered indicative of a potential interaction, then definitive dose-response testing would likely be done in Tier 2 to further identify the potential hazard and characterize risks.