EPA: 2,4-D, Glyphosate, Imidacloprid Among Pesticide Chemicals Not Endocrine Disruptors

Nearly three dozen pesticide chemicals tested by U.S. Environmental Protection Agency for their potential to disrupt the endocrine system have been deemed safe enough to not require a second stage of testing. The testing assessed a number of common pesticides including 2,4-D, glyphosate and imidacloprid.

The EPA released its reviews of the Tier 1 screening assay results for the first 52 pesticide chemicals (active and inert ingredients) in the Endocrine Disruptor Screening Program. According to the EPA, this is an important step in a multi-step process to protect public health and the environment by ensuring that exposure to chemicals does not result in adverse effects that can occur from the disruption of hormones.


According to the report, “There was no evidence for potential interaction with any of the endocrine pathways for 20 chemicals, and for 14 chemicals that showed potential interaction with one or more pathways, EPA already has enough information to conclude that they do not pose risks.  Of the remaining 18 chemicals, all 18 showed potential interaction with the thyroid pathway, 17 of them with the androgen pathway, and 14 also potentially interacted with the estrogen pathway.The Tier 1 screening data are the best way to determine whether a chemical has the potential to interact with the endocrine system and requires more thorough testing.”

2,4-D, glyphosate and imidaclopid were among those pesticides the EPA indicated need no further testing.For the chemicals that the EPA decided need no further testing, a report accompanying the results included a paragraph similar to the one written for glyphosate: “Based on weight of evidence considerations, mammalian or wildlife EDSP Tier 2 testing is not recommended for glyphosate since there was no convincing evidence of potential interaction with the estrogen, androgen or thyroid pathways.”

EPA currently uses a two-tiered screening program that examines chemicals to determine whether they have the potential to affect endocrine systems. The first step is Tier 1 screening, which uses a battery of 11 assays to determine whether chemicals have the potential to interact with the estrogen, androgen or thyroid hormonal pathways. For each chemical, EPA decides whether additional (Tier 2) testing is necessary. These decisions are based on weighing whether the evidence from the assay results and other scientifically relevant data, shows more potential for endocrine bioactivity than the evidence that it does not.

The first 52 chemicals to be screened were not selected because of their potential to interact with endocrine systems but rather for their potential for human exposure. It is important not to equate a chemical’s bioactivity with the conclusion that the chemical harms the endocrine system in humans and wildlife. Bioactivity is an indicator that a chemical has the potential to alter endocrine function, but without further testing, one cannot determine (1) whether the chemical actually alters endocrine function and (2) whether that altered function produces an adverse outcome in humans and animals.

More information, including the screening assessment results, can be accessed here.