EPA's Endocrine Disruptor Screening Program (EDSP) uses a tiered approach for determining whether a substance may have an effect in humans that is similar to an effect produced by naturally occurring estrogen, androgen, or thyroid hormones. The core elements of the EDSP are setting priorities for chemicals to be screened and tested, Tier 1 Screening, Tier 2 Testing, and hazard assessment.
EPA published an approach modeled partially after the compartment-based priority setting approach described in the December 28,1998, Federal Register Notice [PDF, 28pp., 228KB, About PDF] in which EPA provided details about, and requested comment on, its EDSP (63 FR 71542). EPA's approach for selecting the initial 50 to 100 chemicals for Tier 1 Screening, Chemical Selection Approach for Initial Screening in an FR Notice [PDF file, 17pp., 125KB, About PDF] focuses on human exposure-related factors rather than on a combination of exposure- and effects-related factors. Although EPA's approach focuses on chemicals with relatively greater potential human exposure, EPA believes that the approach also captures many chemicals with widespread environmental exposures to other organisms.
EPA published the draft list of initial pesticide active ingredients and pesticide inerts to be considered for screening under the Federal Food, Drug and Cosmetic Act for public notice and comment in a June 2007 Federal Register Notice [PDF file, 18pp., 131KB, About PDF]. The draft list was produced using the approach described in the September 2005 Federal Register Notice [PDF file, 17pp., 125KB, About PDF], and includes chemicals that the Agency has decided should be tested first, based upon exposure potential.
This list should not be construed as a list of known or likely endocrine disruptors. Nothing in the approach for generating the initial list provides a basis to infer that any of the chemicals selected interfere with or are suspected to interfere with the endocrine systems of humans or other species.The first group of chemicals identified for testing includes pesticide active ingredients and High Production Volume (HPV) chemicals used as pesticide inerts. After considering comments on this draft list of chemicals, EPA will issue a second Federal Register Notice containing the final list of chemicals.
Tier 1 screening will include a battery of screening assays that would identify substances with the potential to interact with the estrogen, androgen, or thyroid hormone systems.
View the current status of the assays.
The three goals of Tier 2 assays include:
- Determining whether a substance may cause endocrine-mediated effects through or involving estrogen, androgen, or thyroid hormone systems,
- Determining the consequences to the organism of the activities observed in Tier 1, and
- Establishing the relationship between doses of an endocrine-active substance administered in the test and the effects observed.
The Tier 2 tests are longer in duration than Tier 1 tests and are designed to encompass critical life stages and processes as well as a broad range of doses, and are intended to be administrated by a relevant route of exposure. These tests will enable EPA to obtain a more comprehensive profile of the biological consequences of a chemical exposure and identify the dose or exposure that caused the consequences. Effects associated with endocrine disruption may not be expressed until later in the test subject's life, or may not appear until the reproductive period is reached. Therefore, Tier 2 tests usually encompass two generations and include effects on fertility and mating, embryonic development, sensitive neonatal growth and development, and transformation from the juvenile life stage to sexual maturity.
Tier 1 Screening and Tier 2 Testing data collected as part of EDSP will help EPA to identify and characterize hazard (the potential to cause harm). When EPA integrates and interprets all of the endocrine disruptor-related hazard data in consideration with other available hazard information, EPA performs a hazard assessment. EPA will then conduct an exposure assessment by looking at the amount of chemical to which wildlife or humans are likely to be exposed. The final step in the process is the risk assessment, through which EPA integrates the information about the potential harm of a chemical with the likelihood that someone or something will be exposed. Based on scientifically sound risk assessment the Agency can make risk management decisions regulating the chemical(s). For more information about how EPA conducts health risk assessments, read EPA's Office of Pesticide Programs' fact sheet entitled, "Assessing Health Risks from Pesticides".
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