Explanation of the Endocrine Disruptor Screening Program's Tier 1 Tests
Agency Issues Clarifications on Endocrine Disruptor Screening Program Tier 1 Assays
The United States Environmental Protection Agency (EPA) has provided detailed clarifications regarding the technical aspects of the Tier 1 assays used in the Endocrine Disruptor Screening Program (EDSP). These clarifications address a range of questions from test order recipients and other stakeholders, providing a more comprehensive understanding of the assays and their applications.
The document "Clarifications on Technical Aspects of the Tier 1 Assays" (622.89 KB) is available, offering insights into the composition, purpose, and scope of the Tier 1 battery. The battery includes various assays targeting critical endocrine pathways, such as Estrogen Receptor Binding, Androgen Receptor Binding, Aromatase activity, Estrogen Receptor Transcriptional Activation, Amphibian Metamorphosis, and a variety of rodent and fish assays.
The Tier 1 assays serve as initial screening tools to determine whether a chemical substance may interact with or disrupt the endocrine system in humans or wildlife, guiding decisions on the need for more comprehensive Tier 2 testing. The Agency recognizes that while the Tier 1 assays focus primarily on the estrogen, androgen, and thyroid hormone axes, other critical endocrine pathways such as corticosteroid, retinoid X receptor, and PPAR pathways may also be involved in endocrine disruption.
The EPA also released responses to specific technical questions from CeeTox Contract Laboratory about the conduct of in vitro EDSP Tier 1 Assays, such as the Estrogen Receptor Transcriptional Activation (ERTA) Assay and the Aromatase Assay. Additionally, documents addressing questions from Huntingdon Life Sciences regarding the conduct of the EDSP Aromatase Assay Using Guideline 890.1200 and the Estrogen Receptor Binding Assay are available.
The clarifications address simple but significant errors in test guidelines and ambiguous language that required clarification. Examples of errors include incorrect references to tables and misplaced decimal points. The Agency has also responded to questions about whether alternative techniques might be acceptable to use.
The EPA's responses to these questions are available in the provided documents, which can be accessed below. The Agency's guidance and regulatory context ensure that the EDSP Tier 1 test guidelines are finalized to meet statutory requirements under TSCA, FIFRA, and FFDCA, ensuring the assays' design and use align with regulatory mandates concerning human health and environmental protection related to endocrine disruption.
The EPA releases data evaluation records (DERs) and weight-of-evidence assessments for chemicals tested under the Tier 1 assays, providing transparency on assay results and supporting regulatory decision-making. For example, DERs and conclusions for certain chemicals such as trifluralin are published, illustrating the depth of technical documentation available for the assays and their outcomes.
In summary, the Agency's technical clarifications emphasize the standardized, pathway-focused approach of the Tier 1 assays within the EDSP, the current focus on major hormone receptors, ongoing evaluation of test results through detailed data records, and openness to expanding the scope as scientific understanding advances. This framework facilitates consistent screening decisions and informs subsequent Tier 2 testing when warranted.
The Tier 1 assays, fundamental to the Endocrine Disruptor Screening Program (EDSP), can help identify medical-conditions related to endocrine disruption in humans and wildlife. In light of advancements in science and technology, the EPA is open to expanding the scope of these assays as scientific understanding progresses.
