Toxicology Assessment of Endocrine-Active Substances

Abstract

The endocrine system is a complex, interconnected, multidimensional system that comprises a network of numerous tissues, organs, and organelles. To impact these hormonal systems, a chemical may need only to impact the system during the peak, critical developmental time window of exposure, in utero exposure, and persistent, longer term exposure measured in months, years, and even over the course of a lifetime. The endpoints cover developmental, organogenesis, cancer, metabolism, and complicated neural networks.In 1996, the United States Congress directed the US Environmental Protection Agency (EPA), as stated in the 1996 amendments to the Food Quality Protection Act and Safe Drinking Water Act, to identify chemicals with the potential to interact with the endocrine system and, subsequently, to test those that may warrant additional longer term definitive tests for regulatory determinations. To this end, in 1998, the EPA had developed its Endocrine Disruption Screening Program (EDSP), which employs a two-tiered screening and testing approach; together in partnership with the global regulatory community, the Agency had taken up the charge to scientifically develop and validate test methods and issue endocrine test orders to screen and test >50 chemicals since 2009 for endocrine activity and adversity. In its weight-of-evidence determinations for the initial list of 52 chemicals, EPA concluded that while 32 of these demonstrated potential interaction with one or more endocrine pathways only 18 were identified for further testing.