UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

Aaron Colangelo, Esq. 

Senior Attorney 

Natural Resources Defense Council 

1152 15th Street NW, Suite 300 

Washington, D.C. 20005 

Margaret Reeves, Ph.D. 

c~c 1 s 2012 

Senior Scientist/Program Coordinator (Environmental Health and Workers' Rights) 

Pesticide Action Network North America 

49 Powell Street, Suite 500 

San Francisco, CA 941 02 

Re: Chlorpyrifos petition dated September 12, 2007 

Dear Mr. Colangelo and Dr. Reeves: 

I am writing to provide you with an update on the U.S. Environmental Protection 

Agency's (EPA) plans for further responding to the petition dated September 12,2007 

(Petition), submitted jointly by the Natural Resources Defense Council (NRDC) and Pesticide 

Action Network North America (PANNA). The petition specifically requested that EPA revoke 

all tolerances and cancel all registrations for the insecticide chlorpyrifos. 

As you are aware, in a letter dated July 16th of this year, EPA provided you with a partial 

response to six of the 10 claims raised in the petition and outlined its intended approach for 

completing work on the remaining four claims. At the same time, EPA partially granted your 

petition with its response to one part of your inhalation exposure risk claim, announcing that 

EPA was taking action to address risks from primary spray drift by limiting application rates and 

imposing buffer zones around sensitive sites adjacent to agricultural applications. I am pleased 

to announce that registrants have submitted draft amended labels for all agricultural use products 

to implement these additional use limitations. EPA anticipates its approval ofthese 41 amended 

labels by December 31 , 2012. 

In the partial response, we also informed you that EPA intended to provide its written 

response to the remaining issues by December 20 12. We noted that it was our intention that the 

response be informed by the recommendations of the July 2012 FIFRA Scientific Advisory 

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Panel (SAP or Panel) report1 that addressed issues relevant to three of petitioners' remaining four 

claims -- that EPA failed to quantitatively incorporate data exhibiting long-lasting effects from 

early life exposure to chlorpyrifos in children; that EPA disregarded data demonstrating that 

there is no evidence of a safe level of exposure during pre-birth and early life stages; and that 

EPA failed to cite or quantitatively incorporate studies and clinical reports suggesting potential 

adverse effects below 10% cholinesterase inhibition. Further, we also noted in the partial 

response that our work on the volatilization component of the fourth remaining claim (inhalation 

exposure) was also ongoing and would be impacted by the results of the SAP report. However, 

because EPA had just received the SAP report prior to the release of the partial response, EPA 

had not completed its review of the SAP's recommendations at that time. Thus, the extent and 

nature of the work necessary to address those recommendations was an uncertainty. 

The recent SAP report contained several recommendations which require additional 

analyses by EPA to address the toxicology issues raised in your petition. Specifically, the SAP 

recommended that EPA conduct a dose reconstruction analysis of potential exposures to women 

and children studied in the Columbia University-sponsored epidemiology study2 as an approach 

to aid in assessing the degree to which individuals in the cohort may or may not have 

experienced acetylcholinesterase inhibition. In addition, the Panel recommended that additional 

analyses of the epidemiological data be conducted, particularly in the areas of biological marker 

of exposure data and multi-chemical exposures. 

EPA has made progress on the dose reconstruction analysis. However, the analysis ofthe 

biomarker of exposure data and evaluation of the multi-chemical exposures suggested by the 

Panel necessitate that EPA obtain the raw data from the epidemiology study. At this time, EPA 

only has access to summary information provided by the publications, but has been working to 

obtain the original data from the study authors to conduct the needed analyses. 

Two additional considerations have necessitated further analysis of the toxicology issues 

raised in your petition. First, members of the Panel expressed concern during the oral 

deliberations that scientific experts in diagnostic and analytic tools, like those used to assess 

neuro- and motor development of the children in the epidemiology studies, were not included on 

the Panel. Second, after the SAP was held, a new epidemiology study from the Columbia 

University researchers describing the results of magnetic resonance imaging (MRI) on a subset 

of children in the cohort was published. Between August 2012 and October 2012, EPA solicited 

comments from scientists within the federal government who have expertise in these two 

scientific areas and is currently evaluating this input. 

With respect to the volatility of chlorpyrifos, EPA has reviewed a new field volatility 

study recently submitted by Dow AgroSciences in response to the data call-in requirements for 

the chlorpyrifos registration review. EPA is currently working to complete its assessment of the 

1 Available at http://www.epa.gov/scipoly/sap/meetings/20 12/april/041 0 12minutes.pdf 

2 Raub, V., Arunajadai, S., Horton, M., Perera, F., Hoepner, L., Barr, D. B., & Whyatt, R. (2011). Seven-year 

neurodevelopmental scores and prenatal exposure to chlorpyrifos, a common agricultural pesticide. Environ Health 

Perspect, 119(8), 1196-1201. doi: 10.1289/ehp.l003160; Raub, V. A., Garfinkel, R., Perera. F. P., Andrews, H. F., 

Hoepner, L., Barr, D. B., Whyatt, R. W. (2006). Impact of prenatal chlorpyrifos exposure on neurodevelopment in 

the first 3 years of life among inner-city children. Pediatrics, 118(6), e1845-1859. doi: 10.1542/peds.2006-0338. 

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potential risks associated with volatilization from chlorpyrifos applications. The scope and 

content of this on-going assessment is informed by recent risk assessments of field volatility of 

fumigant pesticides

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, Dow AgroSciences' recently submitted chlorpyrifos field volatility study 

coupled with existing volatility data found in the open literature, EPA modeling tools, and the 

report and recommendations from the 2009 SAP meeting4 

on pesticide volatilization where 

chlorpyrifos was one of the case studies presented. 

While EPA has been working diligently, as outlined in the preceding paragraphs, and has 

made significant progress in addressing the recommendations of the SAP and completing our 

response to all four remaining claims in your petition, EPA will not be in a position to provide a 

complete response to the petition this month, as we previously believed. EPA currently intends 

to provide a further response to the petition by the end of January 2013 that will address some, 

but likely not all, of the four remaining claims. To the extent certain issues remain unaddressed, 

the January 2013 response will explain the additional work we will be doing and will set forth 

our anticipated timeline for completing the response. 

Steven P. Bradbury, Ph.D. 

Director, Office of Pesticide Programs 

3 The assessments can be found in the dockets for each fumigant. Four of which are provided here chloropicrinEPA-HQ-OPP-2007-0350; dazomet- EPA-HQ-OPP-2005-0128; metam sodium/potassium - EPA-HQ-OPP-2005-

0 125; and methyl bromide- EPA-HQ-OPP-2005-0123. 4 Available at http://www .epa.gov/scipoly/sap/meetings/2009/december/ 120309meetingm inutes. pdf. 

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