Response to the NRCD Petition 

Introduction  

EPA Should Deny NRDC’s Petition To Revoke 2,4-D Tolerances Because It Is Untimely

NRDC’s Petition to revoke 2,4-D tolerances comes too late. It has had ample opportunity to comment on and object to the 2,4-D tolerances EPA established in accordance with the June, 2005 Reregistration Eligibility Decision (“2,4-D RED” or “RED”) (USEPA 2005). FFDCA § 408(g) requires a person to file objections to a regulation establishing a tolerance for a pesticide chemical residue within 60 days after the regulation establishing the tolerance. EPA established the current 2,4-D tolerances by rule under FFDCA § 408(e) on September 12, 2007 and the period for filing objections expired on November 12, 2007 (US Federal Register 2007b).

Following EPA’s June, 2005 publication of the 2,4-D RED, on June 6, 2007, EPA published in the Federal Register a proposed rule to revoke old (pre-RED) tolerances for certain pesticides, including 2,4-D, in order to establish new tolerances set by EPA in the pesticides’ REDs (US Federal Register 2007a). EPA opened an electronic docket (OPP-2007-0097) and invited public comment by August 6, 2007 on the proposed 2,4-D tolerances. NRDC did not submit comments and on September 12, 2007, EPA published the 2,4-D tolerances in their final form as regulations at 40 C.F.R. § 180.142. (US Federal Register 2007b at 52013). The Agency’s final ruled advised that the 2,4-D tolerances were adopted in accordance with the Agency’s authority under FFDCA 408(e). (Id. at 52015).

FFDCA § 408(g)(2)(A) provides that “within 60 days after a regulation or order is issued under [408(e)] any person may file objections thereto with the Administrator, specifying with particularity the provisions of the regulation or order deemed objectionable and stating reasonable grounds . . . .” NRDC failed to file comments on EPA’s 2,4-D tolerances and failed within 60 days of September 12, 2007 to file objections to the 2,4-D tolerances. It can not now belatedly petition EPA to revoke these tolerances when it failed to either comment on the tolerances when they were proposed and when it failed to timely object to the tolerances in accordance with the § 408(g)(2)(A). With the exception of one 2008 study, NRDC’s petition relies on studies that would have been available to it in 2007. Thus, NRDC’s Petition does not now raise any issues or data that it could not have raised had it filed a timely petition in 2007.

EPA Should Deny NRDC’s Petition Because It Does Not Challenge With Particularity or Specificity EPA’s Quantitative Human or Environmental Risk Assessments

NRDC’s petition (at page 3) recites the basic requirements of FIFRA and FFDCA: 1) EPA may not register or reregister a pesticide if it causes “unreasonable adverse effects on the environment;” 2) EPA may establish a pesticide tolerance for pesticide chemical residue only if “there is a reasonable certainty that no harm will result from aggregate exposure” to the pesticide chemical residue, and 3) the Agency must explicitly assess the risks of any pesticide residue to infants and children. (NRDC Petition at 3). The Task Force does not dispute NRDC’s statement of law. EPA, however, should dismiss NRDC’s petition because it fails to challenge with any particularity or specificity a single EPA quantitative risk assessment for a human or environmental population exposed to 2,4-D.

FIFRA and FFDCA are risk-based statutes under which EPA assesses the risk a pesticide or a pesticide tolerance poses to humans and the environment in order to determine if the pesticide or its residue meets the standards of FIFRA and FFDCA. The Agency assesses a pesticide’s risks through a well defined and well accepted four step paradigm consisting of the following steps: hazard identification, dose response assessment, exposure assessment and risk characterization. To complete the first two steps, EPA reviews principally mammalian and ecotoxicity studies prescribed by the Agency in 40 CFR Part 158. These studies are performed by the pesticide registrant in order to identify a pesticide’s acute, sub-chronic and chronic effects and to determine the dose at which the effects occur and the dose at which the effect does not occur. The latter recognizes Paracelsus’ 15th century principle that “the dose makes the poison.” While the Agency relies principally on the EPA-prescribed studies performed by the registrant to complete the first two steps, the Agency can and does rely on qualified studies from the open literature. To meet the requirements of the 2,4-D Registration Standard issued by EPA in 1988, the Task Force and its members submitted to EPA over 500 GLP studies on 2,4-D and its derivative salt and ester forms.

When assessing a pesticide’s hazard and the dose at which the hazard occurs EPA utilizes an approach it refers to as “weight of the evidence.” “The approach requires a critical analysis of the entire body of available data for consistency and biological plausibility.” Federal Register Oct. 26, 2007 at 60933, 60937 (US Federal Register 2007c). In making a weight of the evidence assessment, the Agency looks to sufficiency of data, quality of data, evidence of causality, and whether the study corroborates its findings. (Id.) “Weight-of-evidence is not to be interpreted as simply tallying the number of positive or negative studies.” (Id.) A fundamental weakness of the NRDC petition is that it selectively cites only the studies that it believes supports its position, regardless of the study’s quality or its relevance. The NRDC petition does not undertake to look critically and objectively at all the studies on an endpoint and assess the weight of the evidence.

In determining the dose at which a pesticide may cause a short, intermediate or long term effect, the Agency applies a 10x interspecies extrapolation factor and another 10x factor for intraspecies variation. The FQPA requires the Agency to apply another 10x factor to protect children and infants. EPA reduced the 10x FQPA safety factor for 2,4-D to 1x because “the Agency has no residual concerns for the effects seen in the developmental toxicity studies.” (USEPA 2005 at 19). EPA, however, did apply an additional 10x factor to account for the lack of a developmental neurotoxicity study, a relatively new requirement. (Id.) As well, EPA may adjust for factors such as the amount of the pesticide that will be absorbed through the skin.

EPA assesses human exposure to pesticides through inhalation, skin and oral routes. In assessing exposure, the Agency may use data collected from actual exposure studies, or it may calculate exposure based on computer models that conservatively estimate exposure to a pesticide through, for example, the diet or drinking water

In the fourth and final step EPA divides estimated exposure levels for occupational and residential populations by the dose level which produces no observed adverse effect in the animal studies, as adjusted by the safety factors discussed above. This calculation results in a margin of exposure (“MOE”). EPA typically considers a margin of exposure above 1,000 to be adequately protective of humans. If an MOE falls below 1000, EPA will impose a risk mitigation measure and if a risk mitigation measure is not adequately protective then the Agency may require use rate reductions and/or cancel one or more of the pesticide’s uses. The counterpart for an environmental risk to terrestrial and aquatic animals and plants is a quotient expressed as Level of Concern (“LOC”). Levels of regulatory concern for environmental effects range from 0.005 to 1. Tables in the 2,4-D RED report the human and environmental risk quotients for the herbicide.

EPA should dismiss NRDC’s petition because it fails to challenge a single particular EPA human health or environmental risk quotient in the Agency’s 2,4-D RED: that is, it does not challenge a single MOE for an exposed human population or a single LOC for an exposed environmental population. Thus, NRDC must do more than selectively cite studies to claim that 2,4-D presents an endocrine, neurodevelopmental or mutagenic effect or that EPA underestimated the contribution of a route of exposure. NRDC must explain with specificity and particularity how an alleged effect or an alleged exposure impacts EPA’s four-step risk assessment process and how the effect or exposure would change a particular MOE or LOC in EPA’s RED. At the end of the day, NRDC’s Petition falls substantially short of this mark and for this reason alone, EPA should deny the Petition.

2,4-D Is Not Present in Fifty Percent of Water Samples

The NRDC petition starts off on shaky scientific grounds. The Petition’s Introduction (second paragraphs) claims that "2,4-D is found as a contaminant in about half of all surface water samples across the U.S. … ." NRDC cites as support for this claim "Extension Toxicology Network. 1993. http://extonet.orst.edu/pips/24-D.htm  (citing Howard, Philip H. Handbook of Environmental Fate and Exposure Data for Organic Chemicals. Lewis Publishers Chelsea, Michigan.)." The Extension Toxicology Network’s Pesticide Information Profile on 2,4-D, prepared almost 13 years ago in 1996, does not state that 2,4-D is found "in about half of all surface water samples across the U.S." Nor does the parenthetical Howard reference so state. Rather, at page 151 the Howard reference states that "[i]n a U.S. National Surface Water Monitoring Program conducted during 1976-89, 2,4-D was detected in 1.6% of surface waters at a maximum concentration of 1.9 ppb". The Maximum Contaminant Level (MCL) and Maximum Contaminant Level Goal (MCLG) for 2,4-D in drinking water under the Safe Drinking Water Act are both 70 ppb; 1.9 ppb is less than 1/30th of the MCL and MCLG. In short, NRDC’s claim is wrong and unsupported.

EPA’s 2005 2,4-D Reregistration Eligibility Decision (“2,4-D RED”) (USEPA 2005) reviewed the available surface water and groundwater monitoring data for 2,4-D in the Revised Drinking Water Assessment document for the 2,4-D Reregistration Eligibility Decision Health Effects Division Chapter. The EPA-reviewed databases consisted of the USGS National Water-Quality Assessment Program (NAWQA), the USEPA STOrage and RETrieval System (STORET), and USGS Pilot Reservoir Monitoring Study. The maximum 2,4-D concentrations observed were 58 ppb in surface water and 14.8 ppb in groundwater. In the NAWQA database going back to 1991 2,4-D was found in only 0.5% of the 4340 groundwater samples above the LOQ of 0.035 ppb. In the STORET database 2,4-D was only detected above the LOQ in 2.8% of the 21,232 samples.

The EPA developed the National Drinking Water Contaminant Occurrence Database (NCOD) to address requirements of the 1996 amendments to the Safe Drinking Water Act. The database stores data from Public Water System analytical results on finished drinking water. The database shows that 2,4-D was detected in only 0.6 % of the 12,654 samples reported

EPA developed Estimated Exposure Concentrations (EEC) for drinking water from both modeling and monitoring data in the 2,4-D RED and concluded that these concentrations did not exceed Agency’s Level of Concern.

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