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### December 18, 2009 

# 6* 01

Director, Chemical Control Division (7405M) Room 4146 EPA East U.S. Environmental Protection Agency 1201 Constitution Avenue, NW Washington, DC 20004 

### 202-564-4760

Attn:



### Re: David W . Boothe E.1 . du Pont de Nemours and Company Director, Risk Management 4417 Lancaster Pike Wilmington, Delaware 19805 (302) 999-4091



### Document Control Office Office ofPollution Prevention andToxics EPAEast, Room

6428 U.S. Environmental Protection Agency 1201 Constitution Avenue, NW Washington, DC 20004 202-564-8930 

### EPADocket ID Number OPPT-2004-0113 MemorandumofUnderstanding (MOU) between the U .S. Environmental Protection Agency (US EPA) and E. I . DuPont de Nemours and Company (DuPont) for aPerfluorooctanoic Acid (PFOA) Site-Related Environmental Assessment Program(November 3, 2005) Responses to Peer Consultation Panel Input and Outline ofPhase III Work Plan Pursuant to the Memorandumof Understanding Between US EPAand DuPont Company dated December 18, 2009 Dear Sir/Madam

: Attached please find the above referenced document Ifyou need any additional information or further clarification, please contact me at 302-999-4091 .

David Boothe Director, Corporate Risk Management Attachment : Index of the document (1 page) 

### Enclosures: 1 paper copy oftheabove referenced document

1 digital copy of the above referenced document

~ ..i F

### Docket No. OPPT-20040113 December 18, 20#9 2

EPA-DuPont MOU 

### Index Responses to Peer Consultation Panel Inuutand Outline ofPhase III Work Plan Pursuant to the Memorandum

of Understanding Between US EPAand DuPont Company dated December 18

. 2009 Document/Renort Title-Paper Copy No. of Pages* 1 paper copy ofthe Responses to Peqr Consultation Panel 20 pages Input and Outline ofPhase III Work Plan Pursuant to the MemorandumofUnderstanding Between U.S. EPA and the DuPont Company dated December 18, 2009

Document/Report Title-Electronic Copy No . ofPages CD 1 of 1 containing the Responses to Peer Consultation Panel 20 pages Input and Outline of Phase III Work Plan Pursuant to the Memorandum

ofUnderstanding Between U .S. EPA and the DuPont Company dated December 18, 2009 as one PDF file

Page - 2of2 OPPT-2004-0113 PFOASite-Related Environmental Assessment ProgramResponses to Peer Consultation Panel Input and Outlineof Phase III Work Plan Pursuant to the Memorandum of Understanding (MOU) Between US EPAand DuPont Company

December 18, 2009 Introduction In November 2005, the U . S. Environmental Protection Agency (USEPA or EPA) Office of Prevention, Pesticides, and Toxic Substances (OPPT) and E. I . du Pont de Nemours and Company (DuPont) entered into a Memorandumof Understanding (MOU) in which DuPont committed to provide certain data and information on perfluorooctanoic acid and its salts (PFOA) through a Site-Related Environmental Assessment (the Assessment) on and around the DuPont Washington Works Site (the Site) . The goal of the Assessment was to address fully the question referred to as "the Charge", which is as follows: "Are current PFOA environmental releases and sources of those environmental releases fromthe Site and the presence of PFOA in environmental media on and around the Site sufficiently understood so that the pathways of migration and exposure to PFOA associated with that Site are adequately characterized andassessed on a screening level basis?" As defined in the MOUand as used in the Charge, "Exposure to PFOA associated with the Site" refers to current exposures and the potential for future exposures from the presence of PFOA in Environmental Media as a result of current or past Manufacturing Activities at the Site, but does not include an assessment of exposures that may have occurred in the past ." The "Screening Level Exposure Assessment (SLEA) of current human exposure to PFOA associated with the Site shall include a quantitative assessment for any exposure pathway for which the data allow quantitative assessment, and a qualitative or semi-quantitative description of exposure where the data do not allow quantitative assessment" (MOUSectionV . A . 2 . d.). As per the MOU, the Assessment was to be based on Phase I data gathered during activities associated with various Letters of Intent and certain environmental monitoring commitments, along with Phase II data generated through the execution ofthe MOUWork Plan. Recommendations for a subsequent Phase III data gathering stage were to be based on the results of a SLEA. In October 2008, DuPont submitted the following documents, required by the MOU : the Data Assessment Report (DAR), the Screening Level Exposure Assessment for DuPont Washington Works Facility, Parkersburg WY (SLEA), and the Future Data Needs Assessment (FDNA) . These three documents were reviewed by a Peer Consultation Group (PCG) comprisedof eight scientists selected by an Independent Third Party (ITP) [Dr. Mitchell Small of the Civil and Environmental Engineering and Engineering Public Policy Department of Carnegie Mellon University] . The ITP administered the Peer ReviewProcess described in SectionV .E. ofthe MOU

. The PCGmet in Parkersburg, West Virginia on March 23 and 24, 2009, in a public meeting to discuss their comments on the DAR, SLEA and FDNA documents. The ITP and PCGsubsequently issued a final report titled: Final Report ofthe Peer Consultation Panel conducting the review for the Scientific Peer Consultation Processfor a Site Environmental Assessment Programas part of the DuPont - EPA Memorandumof Understanding and Phase II Workplan (PCP Final Report or Final Report) on July 15, 2009. This document is the final Meeting Report referenced in MOUSectionV .E.2.1 .-n . (Note: that while the Panel referred to themselves as the Peer Consultation Panel (PCP), we shall refer to themas the Peer Consultation Group (PCG) as per the MOU .) As required by MOU Section V .E.2.m ., EPAprovided further input to DuPont in a letter dated September 24, 2009 fromJim Willis, Director, Chemical Control Division, OPPT, to Andrew S. Hartten of DuPont.As required by the MOU Section V .E.2.n., DuPont is, by this submission, providing its written response to the input fromthe PCG as summarized in the final Meeting Report and to the input received from EPA

. As EPAagreed "with the Peer Consultation panel's assessment of the quality and quantity of the data collected and the ability of the existing data to meet the Charge as defined in the MOU" and did not specify any additional and separate guidance in the referenced letter, DuPont has based its response directly on the PCG comments, which are summarized in Section 3.7 ("Summary of Priority Data Needs for Future Study Phases") ofthe Final Report . General Response DuPont commends Dr . Small and the PCGmembers for their thorough and thoughtful reviewof the documents submitted. The Phase III Work Plan Outline (attached) was informed by careful consideration of the PCP Final Report . However, we do believe that some of the recommendations in the Final Report were shaped by an overly broad interpretation of the Charge which went well beyond the screening level approach specified in the MOU(and as described above) . Accordingly, the Phase III Work Plan Outline was also informed by careful consideration of what additional data and other information is needed to fully address theCharge. In assessing future work for Phase III, we also took into account other considerable activities conducted for purposes other than this MOU, but which are intended to ascertain exposure to PFOA of the community and environment surrounding the Washington Works site. These other studies already completed, or underway, strive to fully characterize the exposure of the community surrounding the Site. We further believe that actions already taken to substantially reduce emissions and environmental and community exposure along with the planned complete phase out of PFOA use at the site by 2015, or sooner ifpossible, are highly relevant when considering Phase III activities. None of these factors were envisioned when the MOUwas signed in 2005, but they are highly relevant and must be considered when determining what Phase IIIwork is truly additive going forward. These factors (further examined below) lead us to conclude that the recommendations set forth in the FDNA for Phase III are the most appropriate course based on the SLEA . Specifically, the Phase III Work Plan focuses mainly on gathering additional data on locally grown produce and milk consumed by the local community, which is consistent with the PCGrecommendations to address those particular data needs. Scopeof Work Considerations-"Screening Level Basis" In developing the Phase 11 Work Plan and SLEA, DuPont carefully considered the MOU definitions and EPA guidelines for Screening Level Exposure Assessments to address the Charge. EPA's Guidelines for Exposure Assessment (as required by the MOU) were consulted, as well as OPPT's web site entitled "What is OPPT's Approach to Exposure Assessment?" Ourwork was basedon a reasonably literal interpretation oftheseguidelines. FromEPAguidelines: "A screening level exposure assessment will generate a quantitative conservative estimate of exposure. The screening approach generally involves using readily available measured data, existing release and exposure estimates and other exposure related information. Where conservative estimates of exposure are not available, simple models, which often use generic scenarios andassumptions, maybe used to fill in gaps. " The SLEA did generate quantitative and conservative estimates of exposure, as well as more realistic central estimates of exposure. We considered all of the available data, which were collected in accordance with an EPAor other agency-approvedwork plan.Theguidelines further state: "Exposure assessments may use measured data or model estimates . Representative measured data ofknown quality arepreferred over modelestimates andare needed to validate and improve models. " Per the EPA Guidelines, exposures were quantified for those pathways with data and a conservative modeling of those pathways for which data were not available was conducted. Moreover, although the results ofthe air modeling were not used in the exposure assessment itself, modeled data were used in a weight-of-evidence fashion to enhance our confidence in existing soils data, andourconfidence in the means by which the material came to be there . The data and the SLEA clearly show the primary route of exposure for the local community is drinking water that contains PFOA and that other routes are less significant when considering exposure of the overall population, as was done in the SLEA. In fact, the EPAGuidelines for Exposure Assessment state: "Normally it is neitherpracticable nor advisable to immediately develop detailed information on all the potential pathways, since not all may contribute significantly to the outcome of the assessment.. ... A common approach to estimating exposure and dose is to do a preliminary evaluation, or screeningstep, during which bounding estimates are used, andthen to proceed to refine the estimatesfor those pathways that cannot be eliminated as oftrivial importance. " Accordingly, based on the EPAGuidelines, to the extent that data were available, both reasonable maximum

and central estimates of exposure were developed for the SLEA. For the modeled pathways that could not be eliminated as being "of trivial importance", it is acknowledged that some Phase III work may be appropriate. In all cases, the objective was not to delineate the ultimate geographic extent of PFOA presence around the Site, norwas the ultimate product of thework to be a health-based risk assessment of the local community, although that is certainlyoccurring by other means (see below) . It is noted that some members ofthe PCGdiffered with this interpretation ofthe Charge and much of their subsequent feedback was supportive of a considerably expanded data set that was, based on our interpretation of the Charge and MOU requirements, well beyond the scope required to reasonably complete the SLEA. As Dr. Small notedin Section 2 of the Final Report :

"It should be notedthat members ofthepanel diddiffer in their understanding andexpectations of what was meant in the charge by, "adequately characterized and assessed on a screening level basis . " Some members interpreted this to mean that the migration and exposure assessment should be at the current state-of-the-art in the scientific literature and practice for such assessments, withfull coverage of potential migration andexposure pathways. Others interpreted the term "screening" to implythat asomewhat more initial assessment was intended, whichwould then encompass a more-limitedsampling andevaluation ofa more-limited set ofpathways. " The DuPont Phase II Scope of Work and SLEA arevery much in line with the latter interpretation of the Charge and our subsequent section-by-section response to the Panel's feedback is informed by this approach. Nevertheless, a number of completed or planned state-of-the-art studies of community exposure by other groups, discussed below, will provide data in keeping with the broader aims of the former interpretation described above by Dr. Small . Impact ofOther Relevant Factors on Phase III Scope When determining appropriate Phase III data collection, we believe there are other substantive considerations to be taken into account that fall into three areas: 1) the extent to which collection of additional data will have a meaningful impact on the understanding of exposure on and around the Site 2) the ultimate utility of the data in determining mitigating actions for exposure of the local community and environment, and 3) relevant data obtained through other studies.(1) Collection of Meaningful Data for Understanding Exposure In determining the value of future data collection efforts, the SLEA considered not only the limitations of the existing data, but also the extent to which the collection of additional data to refine the understanding of chemical concentration in the environment would have a meaningful impact on theresults of the exposure assessment . In determining whether additional data are needed for a particular pathway, the SLEA examined each individual environmental medium, the potential exposure rates associated with each medium, andconsidered the adequacy of the mediadataset. (2) Mitigation ofExposure Subsequent to the signing of the MOU, certain actions have already occurred, or are underway, to mitigate or reduce exposure ofthe local communityand environment. Giventhat the objective ofthe MOU was to determine pathways of PFOA exposure to guide development ofways to reduce exposure, then the following major initiatives begun since the MOU was signed are highly relevant to whether additional Phase III data collection areadditive:

Emission Reductions--Washington Works PFOA manufacturing emissions to air, water, and land have been reduced by 99% since 2000through aggressive programs as part of or preceding adoption of the US EPA 2010/15 PFOA Stewardship Programby DuPont in January 2006. Reports provided to EPA document a sharp decline in emissions since 2000 (http-//www

0a Qov/oppt/nfoa/pubs/stewardship/preports3 html) Phase Out PFOA--In January 2007, DuPont announced that we would no longer make, buy, or use PFOA by 2015, or sooner if possible. Work is well underway at the Site to evaluate, qualify, and convert to non-PFOA processing aids to make fluoropolymers and the Site is on track to achievethis commitment. Water Treatment-- Since signing the MOU, DuPont has made granular activated water treatment available to all public and private water districts that contained PFOA at or above a site specific action level of 0 .5 ppb established by EPA as well as the subsequently developed Provisional Health Advisory of 0 .4 ppb . Going far beyond that action level, in fact, DuPont agreed to offer GACfiltration to certain public and private drinking water sources as part of a settlement agreement of a class action lawsuit brought on behalf of residents of the community around Washington Works. The settlement included six public water districts and many private drinking wells. Much of the data collected under Phases I and II of the MOU were in support of these activities and ongoing testing confirms a marked decline of PFOA levels in drinking water pre-treatment . Leachate treatment systems were also installed at the closed Letart and Dry Run landfills tosignificantly reduce PFOA in discharges from these sites. (3) Relevant Data Obtained throughother Studies -Additional Exnosure Studies of the Local Community Since the MOU was signed, significant outside and independent studies were completed, or are underway, to further assess PFOA exposure of the local community and potential effects of that exposure. These studies were done by academic researchers (particularly Dr . Emmett ofUniversity of Pennsylvania) or by the C-8Science Panelformed as part of the Leach settlement. Universitv of Pennsylvania-Emmett Studies Dr . Emmett and his teamexamined routes of PFOA exposure for members of the Decatur (OH) Community Association who consumed drinking water provided by the Little Hocking Water Association (LHWA) . Dr. Emmett selected this community because LHWA drinking water contained the highest levels of PFOA compared to other affected local water providers and he quantified total exposure by testingfor PFOA blood serumlevels. His study determined that drinking waterwas the primary route ofexposure for this community

. The studyalso provided additional valuable information on, and recommended further study of, other potential exposure routes, e.g., locally-grown produce, and on apparent demographic differences in exposure. The study results are also important in determining an empirical relationship between blood serumlevels and drinking water exposure ofapproximately 100 :1 . The results ofthe study were published (Emmettet al . 2006) and shared directly in meetings with the local community. C-8 Science Panel Studies An independent C-8 Science Panel (www .c8sciencepanel .org) is conducting a number of health studies on PFOA in West Virginia and Ohio counties near the Washington Works site to determine if there is any probable link between C8 (PFOA) and any human disease. The Science Panel's work is quite comprehensive and is fully funded by DuPont as part of the Leach settlement. The Science Panel members are: " Tony Fletcher, PhD, London School ofHygiene andTropical Medicine " David Savitz, PhD, Mount Sinai School ofMedicine " Kyle Steenland, PhD, Rollins School of Public Health, Emory University. Ultimately, the Science Panel work is organized into 11 studies based in part upon data fromover 70,000 local residents fromthe communities around the Site. The studies include (withcurrently scheduled completion dates) : " CARDIOVASCULARRISK FACTORS MEASURED INTHE BLOOD 2008 " THE CANCER IMMUNE FUNCTION, LIVER, ANDHORMONE 2009 DISORDERS STUDY BASEDON C8 HEALTH PROJECT " THE COMMUNITYFOLLOW-UPSTUDY 2011 " THE WORKER FOLLOW-UP STUDY 2011 " THE STUDYOF BIRTHOUTCOMES IN THE WHOLE COMMUNITY 2009 " THE STUDYOF BIRTHOUTCOMESAMONGC8 HEALTH PROJECT 2009 PARTICIPANTS " THE GEOGRAPHIC PATTERNS OF CANCERS STUDY 2010 " THE FOLLOW-UP STUDY ON IMMUNE FUNCTION, LIVER, AND 2010 HORMONE DISORDERS " THE EXPOSURE STUDY 2009 " THE HALF-LIFE STUDY 2011 " NEUROBEHAVIORAL DEVELOPMENT STUDY 2011 The results fromthese studies will provide an unprecedented collection of data and insights about the exposure of the local community . All studies have been, or will be, published in peer-reviewed scientific literature. In particular, the Science Panel's Exposure Assessment study itself is nowcomplete and notification of publication has been made by thejournal Epidemiology, Shin et al ., 2009 . Retrospective Exposure Assessment Estimation for Perfuorooctanoic Acid in Eastern Ohio and Western West Virginia. In a symposiumabstract in this publication, the authors note:

"The inhalation pathway dominated exposure in the early years; however, ingestion of contaminated ground water, now supplying most of the drinking waterfor nearby residents, is nowthe main route ofexposure. Contamination ofpublic water systems occurred both via the river through groundwater communication and leaching through the soil . Residents nearest the plant were most affected . Although plant emissions peaked in the 1990's, and are now diminished, contamination ofgroundwater will continuefor some time via soil leaching . "Conclusion Given the scope and depth of the data already generated or being generated by these studies (particularly the Science Panel Exposure Assessment) and the data on hand from MOU Phase II, the Emmett work, and the Science Panel studies, there is a high degree of certainty that the exposure potential associated with the Site has already been characterized using conservative assumptions. It is our beliefthat additional Phase III sampling under the MOU, beyond that already defined in the FDNA, is likely to be redundantor oflimited value.



## Section-By-Secti on Response to PCGFeedback

3.7.1 . ComprehensiveAir Monitoring CommentfromPCG

: "PFOA air emissions were and appear to still remain a large contributor to contamination of drinking water via the air-soil-groundwater route, especially within a fewmile radius of the site and possibly beyond

. " Response to the PCGComment: Several publications confirmthat PFOA air emissions were a major contributor to contamination of drinking water near the Washington Works Site in the past via the air-soil-groundwater pathway (WVDEP, 2003; Davis et al ., 2007; Paustenbach et al ., 2007) . However, the impact of air emissions on groundwater, and therefore drinking water, decreases substantially within a fewmiles fromthe site, as shown in Figure 5.7 of the DAR . Current and future air emissions fromthe Site are not anticipated to contribute significantly to drinking water levels given that air emissions have been reduced 99%since 2000. Comment fromPCG(continuedl "Although DuPont reports a substantial (two-order-of-magnitude) decrease in air emissions by 2006, theamount ofPFOA actually beingemittednow or in thepast is not reported. " Response to the PCGComment: This information was provided in Figure 4.1 of the Data Assessment Report which shows that air emissions were approximately 30,000 pounds in 1999 and were reduced to several hundred pounds by 2006. Reported Site emissions for 2008 were 500pounds, and the expected total for 2009 is approximately 300 pounds DuPon 2008 a-c ; DuPont, 2009 a-d)) . Note that by 2015, or sooner if possible, complete phase-out of ammoniumpertluorooctanoate will eliminate PFOA air emissions fromthe site, removing any impact to groundwater fromongoing air emissions at the Site. Comment fromPCG(continued) : "Without this [emissions] information, it is not possible to perform transport through the surrounding environment. " Resnonse to the_PCG Comment: mass balance calculations for

As discussed above, emissions information was made available to the PCGin Figure 4 .1 of the Data Assessment Report . The comment regarding mass balance is addressed as a part of the response to Section 3.7.6.Comment from PCG(continued) : ' A coordinated, ongoing air monitoring program is needed, including time coincident measurements of emissions, ambient concentrations, and deposition. Monitoring should include direct stack, ambient anddeposition monitoring at time scales sufficient to characterize long-term, seasonal, and diurnal variations in PFOA emissions, concentrations, deposition, and resuspension. Spatial resolution should be sufficient to address vertical variations in concentration that inform flux-deposition processes, horizontal variations across key receptor locations, including the Ohio River, the LHWA well field, and more distant locations needed to determine thespatialextent oftheSite influence . Airsampling should be extended to distances (horizontally) where the influence of local sources disappears and PFOA levels representative ofatmospheric background levels are seen. This strategically holistic data setwill not only quantify current emissions and exposure, but when coupledwith a mass balance modeling approach (see Section 3.7.6 below), will enable the estimation ofenvironmental loadings andexposures associated with historic emissions. " Response to the PCGComment : Additional air monitoring is not necessary to "quantify current emissions and exposure" or to "enable the estimation of environmental loadings and exposure associated with historic emissions", as recommended above because (1) current emissions of PFOA and its presence in environmental media are well understood; (2) sufficient air data are available to conduct a screening level exposure assessment, as required by the Charge; and (3) additional efforts to research air concentrations do notfurther informfuture exposure potential . (1) Current emissions ofPFOA and its presence in environmental media arewell understood Air emissions frommanufacturing at the Site are well understood by DuPont. The technique for quantifying emissions of PFOA to air was described in detail in Appendix 5.2 of the Data Assessment Report . Stacktesting of the three primary sources (over 90%of total mass emissions) was conducted and correlated to operating parameters and production capacity to determine hourly air emissions. This technique has been approved for regulatory reporting and compliance, and is consistent with routine industry practice for calculating air emissions frompoint sources. It is also notable that by 2015, or sooner ifpossible, complete phase-outwill eliminate PFOAair emissions from thesite. The presence of PFOA in environmental media as a result ofair emissions is also well understood. More than 800 samples of ambient air, soil, fish, surface water, drinking water, and groundwater collected between 2001 and 2006 are available to provide a comprehensive description of where PFOA has been transported into theenvironment, and what concentrations are present that mayresult in exposure. (2) Sufficient air data are available to conduct a screening level exposure assessment Almost 100 ambient air data points collected in 2005 were sufficient to characterize air concentrations and to conduct a SLEA for the Washington Works site. These data showed that air concentrations in the community were in the ng/m3 range and generally decrease with distance fromthe site. (3) Additional efforts to research air concentrations do notfurther informfuture exposure potential Inhalation exposure is not currently considered an important exposure pathway in the DuPont SLEA or in any of the published studies which consider the Washington Works population (Shin et al ., 2009; Emmett et al ., 2006) . Therefore, to expend additional effort to further explore and refine PFOA ambient air emissions, especially in light of its phase-out by 2015, or sooner ifpossible, is impractical and does not further informthe potential for exposure in the study population.

### p. 10 .

3.7.2 Spatially Extensive SurfaceWater Monitoring CommentfromPCG

: `A spatially comprehensivesynoptic survey ofPFOA concentrations in the Ohio River is needed to characterize thespatialextent andsource-receptor relationships ofwaterquality impactsfromthe Site. " Response to the PCGComment: Spatial Extent The purpose of investigation activity as stated in the MOU is to determine if the presence of PFOA in the environment is sufficiently understood to enable exposures to be characterized on a screening level basis, not to characterize thespatial extent of PFOAin the environment generally . Surface waterdata fromthe Ohio River that were collected in 2002, 2004, and 2005,were used in the SLEA. These data pre-date the significant (>99%) reduction in PFOA emissions to water fromthe fluoroploymer manufacturing processes. Because of these significant reductions in PFOA emissions to water that discharges to the Ohio River through the Site outlets, there is no reason to believe that PFOA concentrations measured in the Ohio River today would be higher than those measured prior to the reduction in discharges. Associatively, there is no reason to believe that the spatial extent of PFOA in surface water would be anything other than less than pre-reduction conditions. As such, we believe that significant additional understanding of the spatial extent would not be gained by conducting an additional survey of PFOA concentrations in the Ohio River. In addition, we believe that such data, if collected, would not have a meaningful impact on the results ofthe screening level exposure assessment . Source-receptor Relationship of W ater Oualitv Imnacts fromtheSite With regard to characterizing the source-receptor relationship of water quality impacts fromthe Site, we feel that it is already well characterized. Section 3.2.1 of the SLEA describes the exposure pathways evaluated in the humanexposure assessment and identifies surface water as a secondary source of PFOA . Section 3.2.2 of the SLEAdescribes exposure routes. This section identifies incidental ingestion of surface water while swimming and dermal contact with surface water while swimming as potentially complete exposure routes. Section 3.2.3 describes the receptor sub-populations who may contact surface water. These include off-site recreational swimmers and off-site anglers, in which potential surface water exposure is evaluated. In the SLEA, we acknowledge the potential for exposure to PFOA from this media, albeit limited

. The surface water data used to characterize the presence of PFOA in this mediumwere collected in 2002, 2004 and 2005. During that time, and subsequent to it, significant reductions in the mass of PFOA discharged to surface water have occurred. In fact, emissions frommanufacturing have been reduced by more than 99% over conditions in 2000. Based on the pre-reduction surface water data, the SLEA estimated that the typical external exposures to PFOA fromincidental ingestion of surface waterwas 8 .7 x 10-9 mg/kg/day for the typical adult swimmer receptor . Applying the pharmacokinetic relationship developed by Clewell (2009), this external exposure would be roughly equivalent to a PFOA serum level of 0 .07 ug/1, or less than 2%of the U .S. background level of PFOA in human serum . Projected serumlevels fromdermal exposure to surfacewaterwere estimated to be an additional three orders of magnitude lower still . Bearing in mind that these de-minimis exposures fromcontact with surface water were based on pre-emissions reduction surface water data, it follows that any exposure assessment conducted using postemissions reduction data wouldonly show even lower levels ofexposure. We therefore believethat further investigation of the surface water source-receptor relationship will not meaningfully inform our understanding of PFOA exposures in the vicinity of the Site. Restated, we believe that the surface water exposure pathways meet the definition of being "oftrivial importance" and do not merit additional study.

### p. 11

Comment fromPCG(continued) : "Given thesmall number ofrandomly collected Ohio River watersamples that contain detectable levels of PFOA, a more-targeted sampling campaign should be pursued to address the extent to which fugitive emissions of PFOA travel downstream of their entry point. The sampling should be done, if possible, during one day to provide a snapshot of Ohio River contamination. The sampling day would necessarily be planned

for a timeperiod when actual releases areoccurringat the Washington Works Site. Specific samples should be obtained in the immediate vicinity of each of the major outfalls and downstream, in line with the current (as opposed to a transect runningperpendicular to the bank), and should extend downstreamasfar as possible, but in anycase should includeareas known to have drinking water contamination (e.g. at least as far downstreamas Crab Creek or -90 miles) Water samples and attendant sample concentrations should be constructed to yield quantifiable PFOA concentrations in all surfacewatersamples. " Response to the PC

G Comment : As stated above, the purpose ofthis investigation program was notto delineate theextent of PFOA in the environment generally, but rather to inform our understanding of potential human exposures. We believe that the spatial extent of PFOA in surface water downstreamof the Site would be significantly less than originally reported in the DARas aresult ofemissions reduction measures at the Site. Comment fromPCG(contin ued) : "Afew creeks andshallow

water bodies (e.g

., Brinker Runfor Letart Landfill and Lee Creekfor Dry Run Landfill) that,Jlowthrough thelandfills andsediments in these creeks should also be analyzed, as these creeks are conduitsfor PFOA to the Ohio River. High concentrations ofPFOA are possible in these creek waters andsediments. Coincidentfish, sediment and water samples as part ofthe synoptic water qualitysurvey (sic) . " Resnonse to the PCGComment: We believe that analyzing water and sediments fromcreeks and shallowwater bodies that flow through the landfills would only be relevant for evaluating exposure to an individual exposed to those media, and not for evaluating exposure at a population or sub-population level . In addition, we believe that the collection of additional data on the concentrations of PFOA in fish and sediment would not have a meaningful impact on the results of the screening level exposure assessment. (See responses to PCG Comments 3.7.3. and 3.7.5.) 3.7.3 Intensive River Sediment Monitoring Comment fromPCG

: "Bottom sediment samples need to be obtainedfromthe Ohio River in areas immediately adjacent to Washington Works outfalls, upstream, and downstream, as well as downstreamof the landfill sites. Transects should be designed to capture the extent ofPFOA contamination related to a specific outfall and should include differential depth analysis. " Resnonse to the PCGComment: We believe that these additional data, if collected, would not have a meaningful impact on the results of the screening level exposure assessment. The SLEA identified sediments as a potentially complete exposure pathway. However, exposure to sediments was not quantified, as this pathway was believed to pose a lower potential for exposure to surface water and sediment receptor subpopulations (i .e. fishermen and swimmers) than direct contact with surface water itself. This is supported by the fact that PFOA has a limited tendency to partition into sediments fromsurface water. Higgens and Luthy (2006) measured the soil-water partition coefficient for PFOA in sediments to be 115 ml/g. Assuming a

### p. 12

conservative organic carbon content for the Ohio River sediments of 5%, the resulting distribution coefficient (Kd) would be approximately 5.7 1/kg. This indicates that at steady state, based on the average PFOA concentration in the Ohio River (0.36 ug/1), the concentration of PFOA in the Ohio River sediments would be expected to be -2 ug/kg . This would assume equilibriumconditions betweenthe riverwaterand the river sediments

. However, a river such as the Ohio tends to have some amount of sediment scouring andtransport, thus tending to further reduce the concentration of PFOA expected to be present in sediments in the vicinity of the Site. Given the predicted lowlevels of PFOA in Ohio River sediments, exposure to this medium

would not be expected to occur at levels that would have a meaningful impact on the outcome ofthe Screening Level Exposure Assessment. Comment

fromPCG(continued) : "A related need is to sample a sediment transect runningfromthe Site across the river to the LHWA. This transect would be designed to detect the existence ofany seepagezones emanatingfromthe Riverbank Landfill (RBL) that could potentially have released PFOA that subsequently migrates to the LHWA. Careful study and design will be needed to determine the appropriate depth(s) of sediment retrieval along with the monitoring of the water-bearing zones associated with the Riverbank Landfill and Anaerobic Digestionponds preandlorpost installment ofan engineered cap system, to thoroughly examine this potential PFOA transportpathway . " Response to the PCGComment: DuPont does not believe that groundwater emanating from the RBL seepage zones, ifthey existed, could migrate to LHWA well field. Perchedgroundwaterwithin the Holocene overbank deposits at the Site does exist as indicated by the variable groundwater elevations measured in these low permeability silts and clays (Table Aof Appendix 3.1 in the DAR) . Groundwater in these low permeability silts and clays in the vicinity of the former Anaerobic Digestion Ponds slowly migrates downward and reaches the underlying aquiferwhere groundwater flowis towards the Ranney Well (Figure 3.8 of the DAR) . If this groundwater were to discharge towards the Ohio River as seeps through the bank sediments, either above or below the surface of the river, this water would migrate into the river, mix with the riverwater and flowdownstream with the river water. Given the flowin the river and the distance fromthe Site to the LHWA well field, there is no scientific basis to believe that PFOA seeps, if any, wouldovercome the downstreamcurrent and disperse across theriver to the LHWAwell field . In addition, thecontinuous pumping ofproduction wells on both sides ofthe Ohio River produces agroundwater divide under theOhio River, with water on the north side ofthe river flowing through the river bottom

recharging the LHWAwell field, andwith water on the south side of the river flowing through the river bottom

recharging the Site's alluvial aquifer. There is no scientific basis to believe that any PFOA seeping through the sediments in the vicinity of the Riverbank Landfill andthe former Anaerobic Digestion Pondswould be able to overcome theground water divide and flow under the river in these sediments to reach the LHWA well field. 3 .7.4 Groundwater Pump and Tracer Test Comment.fromPCG

: "Pump and tracer tests are needed to further explore possible hydraulicconnections between the Ohio River waters near the Site andgroundwaters on both sides ofthe river. These are needed to support assessments ofthe potentialfor off-site transport scenarios that mayoccur with changes in pumpingofthe Ranney Well, the DuPont-Lubeck Well Field, or the East WellField, andwhether or notpumpingat LHWA induces any unexpected hydraulic connection between the groundwater associated with the Anaerobic Digestionponds andwaters that eventually enter the LHWAwellfield . "

### p. 13

Response to the PCGComment : P ump and Tracer Tests DuPont does not believe that conducting pump tests, tracer tests, or the options suggested by the PCGdescribed in Section 3.7.4 would provide significant additional understanding ofthe groundwaterflow between the DuPont Site and the LHWA. As stated above, the groundwater divide under the Ohio River does not allow

for groundwaterfrom

thesite to migrate to the LHWA well field. Field measurements of groundwaterelevation data from the Site and LHWAshow that riverwater recharges the alluvial aquifer under the Site and LHWA due to the pumping of the production wells on each side of the river. PFOA concentration data combined with groundwater elevation data indicate the following groundwater flowpathway at the Site (which is depicted in Figure G of Appendix 3.1 in the DAR) : Perched groundwater within the Holocene overbank deposits exists as indicated by the variable groundwater elevations measured in these low permeability silts and clays (Table AofAppendix 3.1 in the DAR) . Groundwater in these lowpermeability silts and clays in the vicinity of the former Anaerobic Digestion Ponds slowly migrates downward and reaches the underlying aquiferwhere groundwater flowis towards the Ranney Well (Figure 3.8 ofthe DAR) . As stated previously, ifthis groundwater were to discharge towards the Ohio River as seeps in the banks either above or below the surface of the river, this water would migrate into the river, mix with the river water andflowdownstream with theriver water. Giventheflowin the river andthedistance from the Site to the LHWAwell field, there is no scientific basis for concern that this PFOA would disperse across the river to the LHWAwell field. Once groundwater reaches the underlying aquifer, the groundwaterdivide under theriver (induced by the pumping of production wells on both sides of the river) and the continued pumping of the on-site production wells prevents groundwater within the site alluvial aquifer frommigrating off -site, with the exception of some limited off-site groundwater migration that maybe happening in the northwest corner of the Site in response to pumping of Sabic (the current owners of the former GE Site) production wells (Figure 14Aofthe Appendix 3.2 ofthe DAR) . With regard to pump tests or tracer tests, DuPont believes that significant additional understanding would not be gained of the hydraulic connections between the Ohio River near the Site and groundwaters on both sides ofthe river by conducting these tests. Conducting these tests on either side of the river may provide limited additional details regarding aquifer characteristics near the specific wells in which these tests are conducted, but would likely not result in significantly increased understanding of groundwater flow within the LHWA or DuPont alluvial aquifers. Furthermore, we do not believe that this additional data, if collected, would have a meaningful impact on the results of the screening level exposure assessment . Comment fromPCG(continued) : "Modeling in agreementwith previously reported datafromthe USGSfor the Parkersburg region indicates a groundwater divide under the Ohio River, which inferred minimal PFOA transport of the Washington Works Site. However, this modeling effort is in need offurther validation, given the very high PFOA concentrations observed in the wells immediately north of the ADP (even after pond material was removed) andwhat appears to be increases in PFOA concentrations in the water beingpumped out by the LHWA. The latter may be due to only contributions fromwet/dry deposition and run offdown the west slope ofdepositedPFOA; however, sufficient uncertainty warrantsfurther data collection. Options include monitoring for PFOA in existing or new wells on the bank of the river and monitoring of water level measurements on both sides of the river to determine drawdown in conjunction with recorded pumping conditions. "

### p. 14 ,

Revision and Expansionof the Groundwater Flow Model for theSite Monitoring of PFOA in existing wells on the banks of the river and monitoring of water level measurements on both sides of the river to determine drawdown in conjunction with recorded pumping conditions, has been conducted previously on numerous occasions. The data obtained was utilized in the revision and expansion ofthe groundwater flow model for the Site andsurrounding area (discussed below), including LHWA, and in the development of the site conceptual model that describes the sources and transport pathways fromon-site PFOA sources to on-and off-site environmental media. The revised and expanded DuPont groundwater flow model was validated by comparing field measurements to the model results predicted . The model was further validated by the similarities in results between the DuPont model and a second model developed by the United States Geological Survey (USGS) . DuPont initially developed a groundwater flowmodel for the DuPont Washington Works Site in 1999 (DuPont RFI, 1999)

. In 2002, DuPont revised and expanded the groundwater flowmodel with the following objectives: " to address comments made by USEPAandthe U .S. Army Corps of Engineers (ACOE) on the original model " to address comments fromthe members ofthe C-8 Groundwater Investigation Steering Team (GIST) that was established by the Orderon Consent " to evaluate groundwater migration pathways at the site under current and regional pumping conditions (including the LHWA well field), and " to evaluate groundwater migration pathways undervarious pumping scenarios. Data Utilized for the Revised Groundw ater FlowModel Included in the revision and expansion ofthe DuPont groundwater flow modelwas general data for theOhio River such as: " Lithology, thickness and depositional historyofthe Ohio River alluvial sediments " Historical low

water levels ofthe Ohio River " Terrace ages and elevation . In addition to thesegeneral data listed above, site-specific data for the areas encompassed within the model were obtained fromWest Virginia Geological Survey publications, RFI reports submitted to regulatory agencies fromDuPont and Sabic (the current owners of the former GE Site), and from documents provided by public water suppliers (LHWA, Belpre, and Lubeck), along with additional data fromDuPont . These site-specific data types included: " well and soil borings " lithologic descriptions " groundwater elevation measurements, includingtwo rounds of synoptic groundwater levels " aquifer testing results " aquifer hydraulicconductivity data " grain size analysis results " estimated recharge rates " daily, and in some cases hourly, pumpingrate data. The model revision and expansion work included input fromexperts at the USEPA, the ACOE, and the USGS and fromthe GIST. Feedback was provided to DuPont by these experts after they reviewed the work completed at key stages in the model revision and expansion. The revised model, and results from the model are documented in the Revised Groundwater Flow Model, Washington Works, Washington, WV that was submitted to the GIST by DuPont in January, 2003 (revised model report; DuPont, 2003) and was included as Appendix 3.2 ofthe DAR .

12

### p. 15

It should be noted that this groundwater model (current conditions) is a representation of actual site hydrogeologic conditions (e. g. aquifer potentiometric surface, gradients, etc.) based on actual field measurements from 84 observation wells. A model is considered valid when its simulation of current conditions matches those displayed by the actual field measurements. Figure 12 of the revised model report shows excellent correlation betweenthe model predicted results and the actual field measurements. SimulatedGroundwater Pumpin¢ Scenarios As stated above, two of the objectives of the model revision and expansion were to simulate groundwater migration pathways at the site under current and regional pumping conditions (including the LHWA well field), and to predict groundwater migration pathways under various pumping scenarios. Section 6

.0 of the revised model report provides the results of several pumping scenarios including: " Current pumping conditions

. No DuPont pumping " No Sabic (the current owners of the former GE Site) pumping " No pumping by DuPont or Sabic (the current owners ofthe former GE Site), and " No LHWApumping Current pumping conditions simulated in the model included pumping of a total of 44 of 50 production wells at Belpre PWS, Blennerhassett Island, LHWA, DuPont Washington Works, Sabic (the current owners of the former GE Site), and Lubeck PSD (Section 4 .2.4 and Table 4 of the revised model report). These pumping conditions are typical in that pumping is normally continuous in order to supply sufficient water to meet the needsfor the public water systems and manufacturingactivities at the industrial sites. Under current pumping conditions, a groundwater divide is predicted beneath the Ohio River in the Pleistocene alluvium(Section 6 .2 and Figure 14Aofthe revised model report) with groundwater in the north side of the river flowing towards the north and groundwater in the south side of the river flowing towards the south

. As noted in the Section 3.7 .4 ofthe PCGFinal Report, the existence ofthis groundwater divide is in agreement with published data fromthe USGS for the Parkersburg region (Kozar and McCoy, 2004) that also indicates a groundwater divide under the Ohio River due to pumping on both sides of the river. Although the USGS model was a two-layer model and the DuPont model was a three-layer model, Kozarand McCoy note no discernible differences betweenthe models were found (references, p. 21) . The results of the other four pumping scenarios listed above are provided in Sections 6 .3 though 6 .6 in the revised model report. The only scenario that results in the groundwater divide being overcome and for groundwater from the Site to potentially flowto LHWA is the no pumping by DuPont or Sabic (the current owners of the former GE Site) scenario (Figure 18 of the revised model report) . Conversely, the only scenario that results in the groundwater divide being overcome and for groundwater fromLHWA to potentially flowto the Site is the no pumping at LHWA scenario (Figure 19 of the revised model report) . Given that the pumping of production wells at the Site began in the late 1940s and early 1950s, prior to pumping at LHWA (which began in the late 1960s), and that pumping has essentially been continuous at both DuPont and LHWA since pumping started, there is no scientific basis for concern that groundwater fromthe Site containing PFOA has ever migrated under the river to the LHWA well field. In addition, under the current pumping conditions simulated in the DuPont model, a groundwater divide is not predicted in the underlying bedrock aquifer beneath thealluvial aquifer andthe Ohio River. Groundwater flowin the bedrock aquifer fromLHWA to the DuPont and Sabic (the current owners of the former GE Site) sites is predicted under the current conditions simulated. Using the revised and expanded groundwater flowmodel, a credible scientific presentation was made by DuPont to EPA Region III to achieve a "YES" determination for the RCRA Corrective Action Environmental Indicator (EI) RCRIS code (CA750), Migration of Contaminated Groundwater Under Control formprepared for the Washington Works site. The "Yes" determination on the formsubmitted by DuPont indicates that migration of contaminated groundwater is under control at the Site. On April 23,

132004, the CA750 form was approved by EPA Region III . This document can be found on the EPA Region III RCRA Corrective Action website. Based in the information presented above regarding the groundwaterflowmodel, DuPont believes that hydraulic connections between the Ohio River waters near the Site and groundwaters on both sides of the river are well understood. However, DuPont believes that collecting another synoptic round of groundwater elevations at the Site, LHWA, Blennerhassett Island, Belpre, Sabic (the current owners of the former GE Site) and Lubeck would provide additional validation ofthe model . This synoptic surveyingwill be conducted in 2010under the Site RCRA Facility Investigation (RFI) activities. PCGPronosed Monitoring Options With regard to the suggested option of conducting additional monitoring of PFOA in wells at DuPont, DuPont has been and still is, required to monitor for PFOA at DuPont and LHWA (as well as at several other public water suppliers along the Ohio River) under several different programs including the Washington Works RFI, the Multi-media Consent Order, SDWA Order on Consent, WV/NPDES permit, and the MOU

. In addition, as part ofthegranulated activated carbon treatment permit for LHWA issued by OEPA, DuPont is required to monitor the PFOA concentration in the prior-to-treatment water (PT), during treatment water (Bedl), and post treatment or finished water (Bed2), as well as in the individual production wells. PFOA data for LHWA and DuPont wells (monitoring, production and temporary wells) was provided in the Data Assessment . Additional PFOA results for samples collected after the submission of the Data Assessment are provided in the Quarterly MOUProgress Reports, the most recent of which was submitted to the Document Control and Director on October 29, 2009. DuPont does not believe that additional monitoring of existing wells located along the banks of the Ohio River that are not currently required for monitoring, or the installation and monitoring of new wells along the Ohio River banks will result in a significantly increased understanding of groundwater flowwithin the LHWA or the DuPont alluvial aquifers, norwould this data have a meaningful impact on the screeninglevel exposure assessment . Comment fromPCG(conti nued) : "Further, tracer tests should be used to delineate potentialpathways between the LHWA andthe former-ADParea in/under the river bed . These pumpingandtracer studiesshouldsignificantly reduce the uncertainty associated with these potentialgroundwater-river waterpathways. " Response to the PCGComment: As discussed in our first response to the PCGcomment for Section 3.7.4, we do not believe that conducting pump tests, tracer tests, or the options suggested by the PCGdescribed in Section 3.7.4 will provide significant additional understandingofgroundwater flowbetween the DuPont Site and the LHWA. Furthermore, we do not believe that this additional data, if collected, would have a meaningful impact on theresults ofthescreening level exposure assessment . 3.7.5 . Additional Biological Monitoring General CommentfromPCG : "There is a need to determine concentrations of PFOA in several biological matrixes to accurately assess exposures via biota to local populations. Although home-grown produce and domestically produced milk have been identified in the Future Data Needs Assessment, it is recommended that PFOA data also be collected for farm produce, locallyproducedmeat, fishfromsurface waters, breast milk samples and game animals (game hen) . These studies should be conducted in conjunction with ongoing biomonitoring surveys of the local population to better coordinate exposure and biomarker estimates . These studies could potentially point to other environmental media and routes of exposure requiring sampling andcharacterization, such as householddust or waterdistribution systems downstream ofcentralized water treatment. "

14

### p. 17

General ResQonse to the PCGComment: The SLEA acknowledged the inherent uncertainty present in virtually every exposure assessment, including itself. Some ofthese uncertainties stemfroma lack of data on select environmental media . In determining the value of future data collection efforts, the SLEA considered not only the limitations of the existing data, but also the extent to which the collection of additional data to refine the understanding ofchemical concentration in the environment would have a meaningful impact on the results of the exposure assessment. In determining whether additional data are needed for a particular pathway, the SLEA examined each individual environmental medium, the potential exposure rates associated with each medium, and aconsideration of the adequacy ofthe mediadataset. In its Guidelines for ExRosure Assessment, EPA states: "Normally it is neither practicable nor advisable to immediately develop detailed information on all the potential pathways, since not all may contribute significantly to the outcomeofthe assessment. Acommon approach to estimating exposure and dose is to do a preliminary evaluation, or screening step, during which bounding estimates are used, and then to proceed to refine the estimates for those pathways that cannot be eliminated as of trivial importance. " In effect, this is exactly the approach that we have taken . To the extent that data were available, the SLEA presented both maximum and central estimates of exposure. For the modeled pathways that could not be eliminated as being "oftrivial importance" (i .e. ingestion of locally-produced milk and produce) we acknowledge that some additional data will be needed to determine their potential significance. The MOUspecified that : "The Screening Level Exposure Assessment ofcurrent human exposure to PFOA associated with the Site shall include a quantitative assessment for any exposure pathwayfor which the data allow quantitative assessment, and a qualitative or semi-quantitative description of exposure where the data do not allow quantitative assessment. " In fulfillment of this goal, the SLEA considered the various potential pathways for human exposure, and then presented both central tendency and upper-bound estimates of exposure for each ofthe various subpopulations forwhichthe data permitted a quantitative examination . In fulfillment of its objective of screening out pathways of insignificant exposure, the SLEA focused on characterizing exposures at a population and subpopulation level, rather than at the level of an individual . The PCG also clearly recognized the legitimacy of focusing on a population level in the screening level assessment, as the PCGFinal Report indicates in Section 3.7.5. that: "There is a need to determine concentrations of PFOA in several biological matrixes to accurately assess exposures via biota to local populations." Many of the comments related to additional data needs characterize exposures to individuals, rather than to populations or subpopulations. For example, the request to sample fish froman individual farmpond would informthe question of whether the fewindividuals who may be fishing in this pond would receive significant exposures from the consumption of fish living there, not the broader subpopulations living in the vicinity of the site. The SLEA is focused on characterizing exposures to populations or subpopulations, not on characterizing exposuresto individuals. As described in the specific responses to comments that follow, we believe that a more complete understanding of the potential exposures to PFOA on and around the Washington Works Site can be developed with the collection of locally-produced milk and produce. Analyses of these two exposure mediawill, either directly or as a surrogate for other related media, inform the question of significance of a number ofpotential exposure pathways. We agree with the the PCG's recommendation of coordinating biological sampling with the ongoing biomonitoring efforts in the surrounding communities . In the section related to this topic, below, we provide an integration of the existing biomonitoring data with an analysis of the results fromthe SLEA, as a means to further demonstrate the degree of understanding of the relationship between environmental levels of PFOA andcommunity exposures. We also include brief discussions ofthe relative significance of the contributions from

some ofthe non-drinking water pathways in the relevant sections, below .

15Specific Resnonses to Specific Elements of the PCGGomment: Samnlin¢ Farm

Produce The PCG comments recommend the collection of farm produce to understand whether consumption of such fruits and vegetables could represent a potentially significant source of exposure to PFOA . In the FDNA, a recommendation was made to collect locally-grown crops to assess the potential exposures to home gardeners and farmers living within a two-mile radius of the Site. The intention in conducting this sampling is to evaluate exposures to the subpopulations that tend to consume a larger proportion of their daily vegetable and fruit intake fromtheir gardens and farms than does the general population. We believe that examining the levels of PFOA in locally-grown crops and evaluating the resulting data using the gardener and farmer receptors, will serve as a conservative surrogate for any broader population who would be ingesting locally-grown crops as a smaller proportion of their daily intake of these foodstuffs. Samulin2 Local ly Produced Meat The PCG comments recommend the collection of locally-produced meat to understand whether consumption ofsuch meat could represent a potentially significant source of exposure to PFOA. The SLEA indicates that the ingestion of meat would generally represent an exposure roughly three to ten-times less than exposure from drinking water, but that it could potentially represent a significant source of exposure to PFOA in those areaswhereexposure via drinking water is lowest . In that context, it is useful to develop data that can help to informthe question of whether or not meat ingestion is a potentially significant source of humanexposure. Pharmacokinetic relationships exist for PFOA that relate the concentration of this compound in blood, milk and flesh (i .e. meat) . As noted in the FDNA, samples of locally-produced milk will be collected and analyzed for PFOA to understand the potential for milk ingestion to represent a significant source of exposure. By using the data fromthe analysis of locally-produced milk in conjunctionwith the pharmacokinetic expressions that describe the relationships between milk and meat, the milk-PFOA data can serve as a surrogatefor the collection and analysis of meat. If, based on an analysis of the milk-PFOA data there is an indication that locally-produced meat could represent a potentially significant source of human exposure, then DuPont will work with EPAto develop an approach for better understanding meat ingestionas a potential source of exposure. Sampling Fish from

Surface Waters As described in the DAR, the fish sampling program collected target fish fromtwo locations in the Ohio River - downstreamof Site Outfa11005, andapproximately 26miles upstream ofthe Site. The objective of the program was to determinethe presence or absence of PFOA in fish tissue. Species with different habitat preferences and foraging modes were considered in the target species selection process. This included predatory fish to serve as an indicator ofpossible bioaccumulation, as well as bottomdwelling fish that mayaccumulate chemicals through direct contact or through the ingestion ofbenthic invertebrates, detritus, or small fish associated with the benthos. Based on this information, the following specieswere targeted for sampling: " Largemouth bass (Micropterus salmoides) " Channel catfish (Ictaluruspunctatus) Threetissue types were analyzed for PFOA fromeach fish sample: " Fillets " Viscera, including the liver " Carcass 16The area immediately below Outfall 005 represented a portion oftheriver that potentially received PFOA fromthe Site; thus, fish collected fromthis area may be exposed to PFOA in the water discharge. The upriver area was selected as a suitable reference location because : 1) it is beyond the influence of PFOA emissions fromthe Site, and 2) it contains similar habitat as the area downstreamofOutfa11005. The summary data indicate that, with the exception of viscera fromcatfish collected near the Site, ranges and averages for each type of fish tissue (filet or carcass) are similar at both locations, and in both species. No correlation was observed when comparing PFOA concentration measured with respect to species, sampling location, age, sex, or length of the samples. The average and the upper 95 percent confidence limit of the mean concentrations of PFOA in fish filets were used to define the exposure point concentrations for the more typical and reasonable maximum exposure scenarios, respectively. The PCG comments recommend the collection of additional fish tissue samples to understand whetherconsumptionof fish could represent a potentially significant source of exposure to PFOA. DuPont believes that the collection of additional data on the concentrations of PFOA in fish will not further informthe question of whether or not fish ingestion is a significant source of PFOA exposure for persons living in the vicinity ofthe Site. There is no reason to believe that fish species other than the two species collected (Largemouth bass and Channel catfish) would be more likely to contain more PFOA than these two species. Moreover, the use of fish tissue data fromfish collected immediately downstream of the Site 005 Outfall likely represents a conservative exposure point concentration because this is the location where the greatest concentration of PFOA in surface waters would be expected to occur. Additionally, there is no reason to believe that fish inhabiting other localwater bodies, such as farmponds or lakes would experience a greater level of PFOA exposure than fish living immediately downstreamof the Site. Even if fish in localized water bodies were to contain higher levels of PFOA, which is unlikely, such presence would only be relevant for evaluating exposure to an individual that may use such a water body forfishing, and not for evaluating exposure at a sub-population level . PBPK modeling using the calculated external doses of PFOA fromfish ingestion was used to estimate the range of internal doses of PFOA that may result fromfish ingestion in the vicinity of the Site. See Table 1 . This analysis predicts an internal dose of 1 .1 ug/l of PFOA in human serum as a result offish ingestion under typical exposure conditions. This represents only about 1% of the mean serum concentration measured in the population living in the vicinity of the Site' . This further underscores the point that fish ingestion is not likely to represent a significant source of exposure to PFOA, and hence collection of additional fish data is notwarranted. Samling Breast Milk As described in the SLEA, recently published studies in the scientific literature indicate the presence of PFOA in human breast milk (Karrman et al . 2007; So et al . 2006; Tao et al . 2008; Volkel et al . 2007) . Thus, although data on PFOA concentrations in breast milk frompopulations living in the vicinity ofthe Site were not available, the potential for infant exposure via ingestion ofbreast milk was evaluated in the SLEA. This was accomplished using information on local serumlevels of PFOA provided in Emmett et al . (2006) and data obtained froma review ofthe scientific literature regarding PFOAin breast milk. Emmett et al . (2006) reported a median serum/drinking water ratio of approximately 105 . This has been recently reaffirmed through work by Clewell, 2009. Tao et al . (2008) reported that the mean PFOA concentration detected in breast milk from45 women in Massachusetts was approximately 1%of the mean reported PFOA concentration in serumfrom female U

.S. blooddonors in the 2003-2004 National Health and Nutrition ExaminationSurvey (NHANES), corresponding to a breast milk/serumratio of 0 .01 . 

### ' Arithmetic mean of the populations served by the six public service districts in the vicinity of the Site containing PFOA, as reported by Steenland, et. al ., October 7, 2008. 17

### p. 20

Comparing the serum/drinking water ratio from Emmett et al . (2006) and the breast milk/serum ratio fromTao et al . (2008) suggests that PFOA concentrations in breast milk would be roughly equivalent to the PFOA levels in drinking water consumed by the mother. Given this relationship, the potential for breast milk to serve as a source of exposure is especially well understood in the population living in the vicinity ofthe Site, given the extensivedegree to which PFOAserumlevels have been studied there. The PCG comments recommend the collection of breast milk samples to understand whether consumption of breast milk could represent apotentially significant source ofexposure to PFOAto nursing infants. Based on the established pharmacokinetic relationships between drinking water, serumand breast milk levels ofPFOA, it does notappear to be necessary to collect breast milk in order to determinewhether it could represent a significant source of exposure in the local population. To the extent that PFOA is present in the drinking water of nursing mothers, studies suggest that similar levels of PFOA will also be present in their breast milk. Sampling Game Animals The PCG comments recommend the collection of game animal samples to understand whether consumption of such biota could represent a potentially significant source of exposure to PFOA to populations living in the vicinity of the Site. Presumably, this comment is referring to game animals that are hunted recreationally, andconsumed as food by hunters and their families. The SLEA did not quantitatively consider ingestion of game animals as a potentially significant route of human exposure to PFOA . We do not believe that it is necessary to sample game animals to evaluate the potential for exposure to PFOA fromingestion of such game. There are two reasons for this. First, while we acknowledge that hunting does occur in the vicinity of the Site by select individuals, it is less clear that hunting, and the consumption of bagged prey, would constitute a practice that is representative of the broader local population. Rather, it would seemto be more associated with a small subset of individuals, whereas the SLEA is focused on a population or subpopulation . Second, most game animals are herbivorous, and data on local wild herbivores indicated a lack of PFOA in their tissues. Although the data were not collected for the purpose of human exposure assessment, they are nonetheless informative in this regard. Small mammals fromthe LHWA well field were collected to determine the levels of PFOA in selected tissues. As recommended by USEPA, the preferred small mammal to be sampled was the meadowvole (Microtus pennsylvanicus) . The meadow vole is almost exclusively herbivorous with insects comprising a very small percentage of the diet . Given this diet, it was selected as the target species optimal for identifying the occurrence of PFOA in small mammals

. The LHWA well field was selected as a sampling location, because it is located directly downwind from

the Site, and transport of PFOA emission from the Site to the LHWAproperty is knownto have occurred. Data from

both liver and blood plasma from voles collected at LHWAshowed no detectable levels of PFOA, despite the fact that PFOA was detected in vegetation that the animals inhabited and, presumably, ingested. To use the meadow

vole as a surrogate for other herbivorous game animals in the assessment of potential exposure to PFOA from ingesting harvested game would, indeed, constitute a conservative approach in two separate regards. First, because the meadow vole has a much more limited home range than other game animals, such as rabbits or deer, one would expect that the fraction of time the voleswere exposed to PFOA would be much greater than other game animals. Second, because the location of the meadow vole sampling (the LHWA) was directly downwind of the Site, one would expect the concentration of PFOA to which the voles were exposed to represent an upper bound surrogate for any other local game animal . Even considering these two points, the meadow voles did not show

detectable levels of PFOA in their tissues. 18

### p. 21

Thus, it seems very unlikely that sampling of other fauna (i .e. non-voles) would informthe question of whether ingestion of game would represent a significant route of exposure to PFOA for populations living in the vicinity of the Site. As such, DuPont is not recommending the collection and analysis ofgame animals. Coordinati nQEx1uosures with Biomarker Estimates The PCG recommended that additional biological monitoring be conducted in conjunction with ongoing biomonitoring surveys of the local population to better coordinate exposure and biomarker estimates. There are two major benefits to considering the recent biomonitoring (i .e. PFOA in serum) data as a part of the present exposure assessment effort andthedesign of subsequent Phase III sampling. First, by using an established PBPK relationship between external PFOA exposures and internal exposures (i .e. serum

levels), we are able to determine the extent to which external exposures have been adequately considered. Put another way, this exercise enables us to determine if there have been any potentially significant exposure pathways that have been overlooked in the SLEA . A summary of the external doses of PFOA fromthe SLEA for all of the major exposure pathways was assembled. Then, usingthe PBPKrelationship from Clewell (2009) serumPFOA levels that would be expected to result from these external exposureswere calculated. This analysis is presented in Table 1 . As shown in Table 1, the predicted MTE level of PFOA in human serumfromthe ingestion of drinking water in the Little Hocking service district using external exposures fromthe SLEA is 490ug/1 . This value aligns very well with the 221-576 ug/1 interquatrile range (mean = 448ug/1) of PFOA serum levels measured in the residences served by the Little Hocking Water Authority (Emmett, et . al ., 2006) . This finding supports the conclusion reached in the SLEA, and by others (Emmett, et. al ., 2006), that drinking water ingestion is the dominant source of exposure for persons living in the vicinity of the Site. Moreover, it reinforced the idea that the major pathways ofexposure were accounted for in the SLEA . The second relevant application of PBPK modeling is in its ability to help focus Phase III data collection efforts on the appropriate exposure media. As noted in Table 1, evaluating modeled exposures fromthe ingestion of locally-produced milk and crops by farmers and gardeners, respectively, predicts PFOA serumlevels in the same range as drinking water exposures for these subpopulations. Based on this finding, we continue to recommend the collection and analysis of locally-produced milk and produce to better understand these sources as potential means for human exposure. 3.7.6 . Implementation ofMultimedia Modelto Evaluate PFOA Mass Balance in Nearby Environment Comment fromPCG

: "A multimedia mass balance modeling approach should be used to synthesize the available information on PFOA mass flowand PFOA mass inventory . This modeling should incorporate available mechanistic understanding of the transport and behavior of PFOA in all relevant media, and address changes in emissions, transport, inventories andexposure over time. It should be used to test whether the available information gives a consistent and sufficiently resolved picture of PFOA exposure pathways related to the

facility, andto identift anddefinefuture data collection needs. " Response to the PCGComment: The recommended mass balance model has been developedfor the Washington Works community covering the years 1951 to 2003 and was published in 2007 by Paustenbach et al . Historical emissions fromthe facility were used in conjunction with various well-acceptedenvironmental models to estimate the concentrations in ambient air, surface soil, drinking water, and homegrown vegetables and to predict potential uptake. Figure 6 of the article depicts the total amount of PFOAused at the Site over the 23 year time period. The mass balance results are shown in Figure 7, entitled "Estimated historical C-8 material balance for the Washington Works Facility from 1951 to 2003 for all processes combined." This figure 19

### p. 22

clearly demonstrates the results of increases in production over time, and efforts to reduce releases to the environment . The article states:

"A simple source mass balance calculation verified that all of the APFO used at the plant was accounted

for in the various environmental media by the model (that is, the amount released over time equaled the amount contained in the various environmental media and nonenvironmental compartments) (Table 17) . The calculations showthat the sum ofthe total mass ofPFOA in each ofthecompartments equals thetotal amount ofAPFOused at theplantforeachyear. " Note that this study, representing cumulative historical emissions through peak emission years (1951-2003), presents a consistent and sufficiently resolved picture of current and historical PFOA exposure pathways related to thefacility. It is also important to note that this study agrees with subsequent exposure assessments that water is the primary route of exposure. Therefore, refinement of this mass balance modelwould not be additive for understanding exposure pathways or additional data needs. Summary As presented above, DuPont concludes that the recommendations set forth in the FDNA for Phase III arethe most appropriate course based on the SLEA. Specifically, the Phase III Work Plan focuses mainly on gathering additional data on locally grown produce and milk consumed by the local community, which is consistent with the PCGrecommendations to address those data needs. PhaseIII Work Plan Outline 1 .0 Introduction 2.0 Data Analysis and Reporting 2.1 Method Development andValidation 2.1 .1 Produce 2.1 .2 Milk 3.0 Locally Grown Produce -Within the 2-Mile Radius of the Site 3.1 Sampling Strategy 3.2 Identification of Sampling Stations 3.3 Sampling Locally Grown Produce 4 .0 Locally Produced Milk Sampling -Within the 2-Mile Radius ofthe Site 4.1 Identification of Sampling Stations 4.2 Sampling Locally Produced Milk 5.0 Data Evaluation 5.1 Locally Grown Produce 5.2 Locally Produced Milk 6 .0 Evaluation of Additional Data Needs 6 .1 Potential Sampling ofLocally Produced Milk-Within 1-Mile of Dry Run and Letart Landfills 7.0 Schedule and ReportingReferences Clewell, H

., 2009. Pharmacokinetic modeling of PFOA and PFOS. The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina, October 15. Davis, K .L., Aucoin, M

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. DuPont, 1999 RCRA Facility Investigation Report, DuPont Washington Works, June 30, 1999. DuPont Corporate Remediation Group and URS Diamond . DuPont, 2003 RevisedGroundwater FlowModel, DuPont Washington Works, Washington, WV, January 2003, DuPont Corporate RemediationGroup and URS Diamond. DuPont, 2008a. Letter fromD . F. Altman (DuPont) to HeatherA . Connolly (WVDEP), regarding Quarterly Air Emissions reporting fromWashington Work site under Consent Order GWR-2001-019, First Quarter Report 4/23/08. DuPont, 2008b. Letter fromD . F. Altman (DuPont) to HeatherA . Connolly (WVDEP), regarding Quarterly Air Emissions reporting from Washington Work site underConsent Order GWR-2001-019, Second Quarter Report 7/21/08

. DuPont, 2008c. Letter fromD . F. Altman (DuPont) to HeatherA . Connolly (WVDEP), regarding Quarterly Air Emissions reporting fromWashington Work site under Consent Order GWR-2001-019, ThirdQuarter Report 10/27/08. DuPont, 2009a

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. F. Altman (DuPont) to Heather A . Connolly (WVDEP), regarding Quarterly Air Emissions reportingfrom Washington Work site under Consent Order GWR-2001-019, Fourth Quarter Report 1/26/09

. DuPont, 2009b. Letter fromD . F. Altman (DuPont) to Heather A . Connolly (WVDEP), regarding Quarterly Air Emissions reporting fromWashington Work site under Consent Order GWR-2001-019, First Quarter Report 4/22/09

. DuPont, 2009c. Letter fromD . F. Altman (DuPont) to Heather A . Connolly (WVDEP), regarding QuarterlyAir Emissions reporting from Washington Work site underConsent Order GWR-2001-019, Second Quarter Report 7/20/09 . DuPont, 2009d

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. F. Altman (DuPont) to Raymond S. Franks (WVDEP), regarding Quarterly Air Emissions reportingfrom Washington Work site under Consent Order GWR-2001-019, Third Quarter Report 10/19/09. Emmett, E

.A., Shofer, F.S., Zhang, H ., Freeman, D

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.. 2006 . Community exposure to perfluorooctanoate: relationships between serum concentrations and exposure sources.J. Occup. Environ . Med . 48(8), 759-770

. Higgins, C

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.G. 2006. Sorption ofperfluorinated surfactants on sediments. Environ . Sci . Technol ., 40, 7251-7256 . Karrman, A, Ericson, I, van Bavel, B, Ola Darnerud, P ., Aune, M

., Glynn, A

., Lignel S., Lindstrom, G . . 2007. Exposure of pertluorinated chemicals through lactation: levels ofmatched human milk andserum and a temporal trend, 1996-2004, in Sweden. Environ. Health Perspect. 115(2), 226-230 .Kozar, M ., D ., McCoy, K

., J., 2004. Geohydrology andsimulation of ground-water flow in Ohio River alluvial aquifers near Point Pleasant, Lubeck, Parkersbury, Vienna, Moundsville, andGlendale, West Virginia U

. S . G . S . Scientific Investigations Report 2004-5088 . Paustenbach D

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.M . 2007. AMethod for Estimating Human Exposure to PerfluorooctanoicAcid (PFOA) : ARetrospective Exposure Assessment of a Community (1951-2003) ;J. Toxicol . Environ

. Health Part A 70, 28-57. Shin, Hyeong-Moo; Bartell, Scott M . ;Vieira, Veronica M

. ; Detwiler, Russell L. ; Steenland, Kyle; Ryan, P . Barry 2009. Retrospective exposure estimation for perfluorooctanoic acid in Eastern Ohio andWestern West Virginia, Epidemiology, 20 (6), S260-S261 . Shinoda, K

., Hato, M

., Hayashi, T., 1972. Thephysiochemical properties of aqueous solutions of fluorinated surfactants. J. Phys. Chem-US, 76, 909-914 . So, M .K., Yamashita, N

., Taniyasu, S., Jiang, Q ., Giesy, J .P

., Chen, K

., Lam, P.K

.S.. 2006. Health risks in infants associated with exposure to perfluorinated compounds in human breast milk fromZhoushan, China. Environ. Sci . Technol . 40, 2924-2929 . Steenland, K, Fletcher, T, Savitz, D ., 2008. Status report: Factors associated with PFOAin a community surrounding a chemical plant. October 7. http://www .c8sciencepanel .org/pdfs/Status Reportfactors associated with C8_levels Oct2008.pdf Tao, L, Kannan, K, Wong, CM, Arcaro, K .F., Butenhoff, J.L. . 2008. Perfluorinated compounds in human milk from

Massachusetts, U

.S.A. Environ. Sci . Technol . 42(8), 3096-3101 . Volkel, W, Genzel-Boroviczeny, O, Demmelmair, H,Gebauer, C ., Koletzko, B

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., Fromme, H

. . 2008. Perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) in human breast milk: Results of a pilot study . Int. J. Hyg

. Environ. Health, 211, 440-446 . West Virginia Department of Environmental Protection (WVDEP) 2003. Ammonium Perfluorooctanoate (C-8) Groundwater Investigation Steering Team Report. West Virgina Division ofWaterandWaste Managment . West Virginia Consent Order No. GW-2001-019°o 0 0 l~ tV '+ M zz zz

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