Response to the NRCD Petition 

Executive Summary

The Industry Task Force II on 2,4-D Research Data ("2,4-D Task Force" or "Task Force") submits these comments in response to the November 6, 2008 petition of the Natural Resources Defense Council ("NRDC") requesting EPA to revoke all tolerances and cancel all registrations for the pesticide 2,4-dichlorophenoxyacetic acid ("2,4-D") (NRDC 2008).

The Task Force respectfully submits that 2,4-D meets the requirements for its continued registration under FIFRA and the continuance of its residue tolerances under the FFDCA and, accordingly, requests EPA to deny NRDC’s petition. From 1988 through June, 2005 when EPA issued the 2,4-D Reregistration Eligibility Decision (“RED”), the Task Force and its members submitted to EPA over 500 studies on 2,4-D, virtually all of which met the Agency’s FIFRA Good Laboratory Practice (“GLP”) standards. The Task Force sponsored and submitted these studies to satisfy FIFRA’s reregistration requirements and the requirements of the Food Quality Protection Act of 1996 that the Agency reassess all tolerances under the Act’s standard of “reasonable certainty of no harm.”

EPA’s reregistration team, consisting of 20 Agency scientists and regulatory personnel, over the course of several years carefully and thoughtfully reviewed the Task Force and other 2,4-D studies to prepare, receive public comment on and revise numerous human and environmental risk assessments on 2,4-D, the end product of which was the Agency’s 320 page 2,4-D RED that determined that 2,4-D met FIFRA’s and FFDCA standards for registration and which served as the basis for new 2,4-D tolerances that the Agency proposed in draft form on June 6, 2007 and issued in final form on September 12, 2008. In certain cases, EPA’s risk assessments identified some uses of 2,4-D where the margin of margin of exposure was inadequate and the Agency required risk mitigation measures, such as protective clothing, as a condition to continued registration. In addition, even though the Task Force had submitted over 500 studies, the Agency required the Task Force to conduct additional studies, such as a new reproduction study and a new developmental neurotoxicity study.

Against the above history, the NRDC filed a petition in November 2008 that summarily claims that notwithstanding the past efforts of the Task Force and EPA over 17 years to develop and review over 500 GLP studies (many of which the Task Force published in peer reviewed scientific journals) and after several years and repeated opportunities for public comment on the Agency’s 2,4-D human and environmental risk assessments, the Agency must now cancel 2,4-D registrations and revoke all 2,4-D tolerances.

The Task Force requests EPA to deny NRDC’s Petition on several grounds, which are set forth in detail below. First, to the extent that NRDC’s Petition requests EPA to revoke 2,4-D tolerances, its Petition is too late. NRDC did not comment when EPA in June, 2007 proposed new 2,4-D tolerances to implement the requirements of the June, 2005 2,4-D RED. EPA issued final 2,4-D tolerances in the form of new regulations on September 12, 2007. NRDC did not file objections to the final 2,4-D tolerances within 60 days of September 12, 2007 as provided for under FFDCA § 408(g)(2). Second, the Task Force requests EPA to deny NRDC’s petition because it fails to state with any specificity or any particularity how or why EPA’s quantitative risk analysis for 2,4-D for human or environmental risks, as set forth in EPA’s June, 2005 RED and its supporting documents, is wrong. Thus, a fundamental flaw of NRDC’s Petition is that it fails to recognize that FIFRA and FFDCA are risk-based laws and the end-product of EPA’s weight of the evidence human and environmental risk assessment paradigm is a number, a risk quotient, that tells EPA that a margin of exposure or level of concern is adequately protective of man and the environment or that it is not. The NRDC Petition fails to explain how or why EPA’s risk quotients for 2,4-D are wrong and for this reason alone EPA should deny the petition.

Even if NRDC’s Petition were timely and even if it were to adequately explain how its concerns relate to EPA’s quantitative risk assessments for 2,4-D, its claims are wrong that 2,4-D causes estrogenic, neurodevelopmental and mutagenic effects and that the Agency failed to conduct an adequate aggregated exposure assessment. The Task Force’s comments review and carefully respond to each claim. The Task Force respectfully submits that the weight of the evidence demonstrates that 2,4-D when used according to its label does not cause estrogenic, neurodevelopmental or mutagenic effects and that EPA has already considered and addressed NRDC’s exposure concerns, as outlined below.

The fundamental weakness of NRDC’s petition is that it does not support its claims with a “weight of the evidence” analysis of all studies that have measured a given endpoint, GLP and non-GLP, but instead selectively cites studies that it thinks supports its view. Many of the studies that it cites were run at excessively high doses that bear no relationship to possible levels of human or environmental exposure. In others, the route of administration (i.e., injected 2,4-D into a rat’s brain) is not relevant to human or environmental routes of exposure. In others, it is impossible to tell what test substance is responsible for an effect (i.e., injecting 2,4-D in a rat after injecting it with Phenobarbital).

The Task Force recognizes and appreciates that even with the benefit of over 500 GLP studies, legitimate regulatory questions may exist and that is the reason Congress included FIFRA § 3(c)(2)(B) in the law that authorizes the Agency to require registrants to submit additional studies. EPA’s 2,4-D RED and its March, 2007 Data Call-In Notice required 2,4-D registrants to conduct and submit a new reproduction and developmental neurotoxicity studies. The Task Force, in close cooperation and consultation with EPA, has combined both requirements into a state-of-the-art extended one-generation reproduction (“one-gen reproduction”) study with 2,4-D. These comments cite preliminary results from the Task Force’s study in response to NRDC’s claims that 2,4-D is either estrogenic or that it adversely effects neurodevelopment.

2,4-D does not cause estrogenic effects

The weight of the evidence does not support NRDC’s claim that 2,4-D is an endocrine disruptor. The Task Force’s ongoing one-gen reproduction study conducted to satisfy EPA’s March, 2007 DCI, which specifically assesses endocrine-related endpoints, will supplement existing in vivo and in vitro studies that demonstrate that 2,4 D does not effect the endocrine system.

2,4-D does not cause neurodevelopmental effects

The studies cited by NRDC do not provide credible or substantive evidence that 2,4-D causes developmental toxicity at exposure levels or routes of administration relevant to humans. To date, there have been no dose-related statistically significant indications of developmental neurotoxicity in the Task Force’ one-gen reproduction study.

2,4-D is not mutagenic

2,4-D acid plus eight different 2,4-D derivatives have been tested in a battery of mutagenicity tests leading to a total of 28 studies submitted in support of reregistration, all of which were negative (non-mutagenic). While EPA acknowledged that some positive mutagenicity studies occur, the weight of the evidence overwhelmingly support a conclusion of minimal or no concern for mammalian mutagenicity for 2,4-D.

EPA has considered exposure through maternal milk

EPA has previously considered and rejected NRDC’s concern. The Agency has stated that it is aware, as a result of animal feeding studies using exaggerated doses that 2,4-D may be present in milk. EPA has previously informed NRDC that its manner of doing risk assessment for infants is protective of any pesticide exposures to infants from human breast milk.

EPA did not underestimate human dermal absorption

Five published studies using human subjects demonstrate that EPA’s dermal absorption factor of 10% was amply protective and higher than the mean absorption rate from the five human studies of 5.7%.

EPA has considered NRDC’s exposure concerns and NRDC fails to explain how its concerns would have changed EPA’s 2,4-D risk assessment

EPA has previously considered and rejected NRDC’s claim that dermal absorption may be enhanced through other factors such as sunscreen, alcohol consumption and insect repellent. Moreover, EPA’s 2,4-D RED required personal protective equipment that mitigate these factors. Several well conducted studies demonstrate that rubber gloves reduce 2,4-D exposure. NRDC’s claim that 2,4-D tracked into homes and persists in carpets for up to one year at concentrations of 0.5 µg/gm is at odds with studies reporting average levels of 0.156 and 0.0475 µg/gm in carpet collected in homes of 2,4-D applicators. Moreover, as noted above, NRDC’s Petition fails to explain how any of its exposure concerns would have altered or changed EPA’s risk assessments.

The Task Force appreciates the opportunity to submit these comments. 

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