Endocrine Disruptors

In July 1998, the U .S. Environmental Protection Agency (EPA) issued a draft list of chemicals for their endocrine disruption High Throughput Screening (HTPS) demonstration studies, in accordance with the Food Quality Protection Act (FQPA) mandate to test chemicals for endocrine effect.


2,4-D was among the first 168 chemicals that had been selected by EPA to go through the tier one high volume-screening test. The 1998 list included chemicals that are in three categories: 1) suspected of endocrine disruption; 2) unknown as to their endocrine potential; and, 3) known to have no endocrine effects with adequate reproductive, developmental and other studies.


2,4-D was placed on the 1998 list in the third category based on two criteria:



  1. Substances known to have no hormonal activity, i.e., negative activity to estrogen, androgen and thyroid receptor transactivation assay (EAT negative).

  2. Substances with adequate and extensive in vivo databases, including developmental and reproduction studies.


Unlike alleged endocrine disruptors, 2,4-D is not persistent in the environment, having a half-life of about seven days. It eventually breaks down to carbon, carbon dioxide and a trace amount of chlorine -all of no toxicological significance. 2,4-D does not accumulate in the body, does not metabolize and is excreted in the urine unchanged.


In summation, under EPA’s classification of potential endocrine disruptors 2,4-D is a Category 3 compound – a chemical “known to have no endocrine effects”.

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