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Overview of the Second List of Chemicals for Tier 1 Screening

As of Tuesday, May 22, 2014, EPA has removed hydrazine and hydrochlorofluorocarbon (HCFC-22) from the Second List of Chemicals for Screening (PDF) (5 pp, 90.1K, About PDF)to allow for further consideration of their physical/chemical properties and/or occurrence in regards to whether these substances are appropriate candidates for testing in the EDSP under Safe Drinking Water Act authority at this time. The U.S. Court of Appeals for the Third Circuit granted EPA’s motion for voluntary partial vacatur and remand regarding these two chemicals.

June 14, 2013– EPA published the Revised Second List of Chemicals for Tier 1 Screening in a Federal Register Notice. This revised second list consists of 109 identified chemicals, 41 of which are pesticide active ingredients (PAIs) and 68 are chemicals identified under the Safe Drinking Water Act (SDWA).


November 17, 2010 – EPA published the second list of chemicals for Tier 1 Screening. This list of 134 chemicals included a large number of pesticides, two perfluorocarbon compounds (PFCs), and four pharmaceuticals (erythromycin, lindane, nitroglycerin, and quinoline). This list also consisted of an array of other chemicals, ranging from those used for industrial manufacturing processes, as plasticizers, or in the production of pharmaceutical and personal care products (PPCPs). 

The public should not presume the listing of a chemical or substance indicates it interferes with the endocrine systems of humans or other species simply because it has been listed for screening under the EDSP. EPA believes that these chemicals or substances should be candidates, at least for screening purposes, under EDSP testing based only on their pesticide registration status and/or because such substances may occur in sources of drinking water to which a substantial population may be exposed.

Basis for Selection

EPA focused on a subset of chemicals and substances that have been listed as priorities within EPA’s drinking water and pesticide programs. First, the Agency identified candidate chemicals that are either contaminants regulated with a national primary drinking water regulation (NPDWR) or are unregulated contaminants that are listed on the third Contaminant Candidate List (CCL 3). EPA began with the 85 regulated drinking water contaminants with existing NPDWRs and the 116 unregulated contaminants listed on CCL 3 because these represent many of the priority contaminants for the drinking water program.

Second, EPA identified candidate chemicals from the Office of Pesticide Programs (OPP) based on pesticides that were scheduled for Registration Review during fiscal years 2007 and 2008. This selection is part of the Agency’s intent to efficiently expedite the testing of pesticides by conducting the testing in parallel or as part of the OPP Registration Review program.

The Agency then consolidated the lists from the Office of Water (OW) and OPP, resulting in over 200 chemicals. EPA streamlined this list by excluding any chemical that fell into one or more of the following categories:

  1. Biological agent and naturally-occurring chemicals (e.g., microbials, microbial toxins, inorganics, radionuclides).
  2. Chemicals for which the manufacturer, importer or registrant cannot be clearly identified (e.g., disinfection byproducts or DBPs, microbes, microbial toxins, degradate compounds with more than one possible source etc.).
  3. Chemicals already included on the first EDSP list.
  4. Chemicals that are hormones with confirmed endocrine effects.
  5. Chemicals that are not likely to be biologically active or which are incompatible with testing assays for various reasons due to one or more of their physiochemical properties (e.g., gases, strongly acidic or basic, solubility, vapor pressure molecular weight).
  6. Pesticides that are scheduled for registration review after FY 2008.

The resulting draft list contained 134 chemicals that the Agency proposed to include in its EDSP.  After a public comment period, EPA has announced in a Federal Register Notice a revised list containing 109 chemicals. Through the issuance of orders, the Agency intends to require the submission of Tier 1 Screening data for these chemicals.

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