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Endocrine Disruption

Overview of the First List of Chemicals for Tier 1 Screening under the Endocrine Disruptor Screening Program

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Overview of the First List of Chemicals

The final list of chemicals for initial Tier 1 Screening under the Endocrine Distruptor Screening Program (List 1) includes chemicals that the Agency, in its discretion, decided should be tested first, based upon exposure potential. The first group of 67 chemicals identified for testing included pesticide active ingredients and High Production Volume (HPV) chemicals used as pesticide inert ingredients (also known as other ingredients). 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 by simply being on this list these chemicals are suspected to interfere with the endocrine systems of humans or other species, and it would be inappropriate to do so.

The final list was developed in response to public comments on the draft list of 73 chemicals.

The Agency deleted six chemicals from the draft list of 73 based upon new information indicating that the chemicals were no longer expected to be found in three exposure pathways. Two of the chemicals, azinphos-methyl and fenvalerate, were removed from the list because all uses of these pesticides had ended or were expected to end before Tier 2 data could be generated in 2012.

The remaining four chemicals were removed based on a reassessment of their uses that confirmed that they would only be expected to be present in two, instead of three, exposure pathways (i.e., the criterion for selecting chemicals for the initial list (List 1) was the presence of the chemical in at least three of the four exposure pathways where the food and occupational exposure pathways were represented). Specifically, aldicarb, allethrin, dichlorvos, and methiocarb, were removed from the initial list because changes in their use and application methods eliminated the potential for exposure in one or more pathways.

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Applying the Chemical Selection Approach

As described in the September 2005 Federal Register Notice, EPA analyzed data for four exposure pathways for pesticide active ingredients and data for four exposure pathways for High Production Volume (HPV) chemicals used as pesticide inerts.

The four exposure pathways identified for pesticide active ingredients include:

  • Food;
  • Drinking water; 
  • Residential use; and
  • Occupational exposure.

The four exposure pathways identified for HPV/pesticide inert chemicals include:

  • Human biological monitoring; 
  • Ecological biomonitoring;
  • Drinking water; and
  • Indoor air.

EPA evaluated the data sources for each pathway to produce four candidate lists of chemicals of pesticide active ingredients and four candidate lists of HPV/pesticide inert chemicals for potential screening. Because there were a large number of chemicals on one or more of these candidate lists, it was necessary to establish priorities for selecting chemicals for initial screening.

Integration of Pathway Priorities for Pesticide Active Ingredients

EPA identified an initial list of 58 pesticide active ingredients to undergo Tier 1 screening in the EDSP. In choosing which pesticide active ingredients to include on the initial screening list (List 1), EPA prioritized to those that:

  • Appeared in four exposure pathways, and
  • Appeared in three exposure pathways where the food and occupational exposure pathways were represented.

Integration of Pathway Priorities for High Production Volume/Pesticide Inerts

EPA identified an initial list of nine HPV/pesticide inert chemicals to undergo Tier 1 screening in the EDSP. In choosing which HPV/pesticide inert chemicals to include on the initial screening list (List 1), EPA gave priority to those that:

  • Appeared in four exposure pathways, and
  • Appeared in three exposure pathways where the human biological monitoring exposure pathway was represented.

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Chemical Substances Deferred from Screening

In September 2005, EPA indicated that the following types of chemical substances may be deferred from initial screening:

  • Certain FIFRA List 4 pesticide inerts (i.e., List 4 inerts are described as "inerts of minimal concern");
  • Most polymers with number average molecular weight greater than 1,000 daltons;
  • Strong mineral acids and bases; and
  • Chemicals that are being used as a "positive controls" to validate the screening assays.

EPA examined the 67 chemicals identified for initial screening in light of the criteria for deferral. None of the chemicals selected for initial screening were categorized as List 4 inerts, high molecular weight polymers, or strong mineral acids or bases. Several of the 67 chemicals, however, have been used as "positive controls" in the validation of individual assays by the EDSP.

None of the selected chemicals identified as EDSP "positive controls" were used in a full battery of Tier 1 screening assays. As a result, none of the chemicals qualify as "positive controls" for Tier 1 screening, as a whole.

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