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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 of Pollution Prevention and Toxics 

EPA East, Room 6428 

U.S. Environmental Protection Agency 

1201 Constitution Avenue, NW 

Washington, DC 20004 

202-564-8930 

EPA Docket ID Number OPPT-2004-0113 

Memorandum of Understanding (MOU) between the U.S . Environmental Protection Agency 

(US EPA) and E. I. DuPont de Nemours and Company (DuPont) for a Perfluorooctanoic 

Acid (PFOA) Site-Related Environmental Assessment Program (November 3, 2005) 

Responses to Peer Consultation Panel Input and Outline of Phase III Work Plan Pursuant to 

the Memorandum of Understanding Between US EPA and DuPont Company dated 

December 18, 2009 

Dear Sir/Madam: 

Attached please find the above referenced document If you 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 of the above 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 Inuut and Outline of Phase III Work Plan Pursuant 

to the Memorandum of Understanding Between US EPA and DuPont Company 

dated December 18. 2009 

Document/Renort Title-Paper Copy No. of Pages* 

1 paper copy of the Responses to Peqr Consultation Panel 20 pages 

Input and Outline of Phase III Work Plan Pursuant to the 

Memorandum of Understanding Between U.S. EPA and the 

DuPont Company dated December 18, 2009 

Document/Report Title-Electronic Copy No. of Pages 

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 of Understanding Between U.S. EPA and the 

DuPont Company dated December 18, 2009 as one PDF file 

Page - 2 of 2 OPPT-2004-0113 PFOA Site-Related Environmental Assessment Program 
Responses to Peer Consultation Panel Input 

and Outline of Phase III Work Plan 

Pursuant to the Memorandum of Understanding (MOU) 

Between US EPA and 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 Memorandum of 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 from the 

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 and assessed on a screening level basis?" 

As defined in the MOU and 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" (MOU Section V. 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 of the MOU Work 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) comprised of 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 

Review Process described in Section V.E . of the MOU. 

The PCG met 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 PCG subsequently issued 

a final report titled : Final Report of the Peer Consultation Panel conducting the review for the Scientific 

Peer Consultation Process for a Site Environmental Assessment Program as part of the DuPont - EPA 

Memorandum of Understanding and Phase II Workplan (PCP Final Report or Final Report) on July 15, 

2009. This document is the final Meeting Report referenced in MOU Section V.E .2 .1 .-n. (Note: that while 

the Panel referred to themselves as the Peer Consultation Panel (PCP), we shall refer to them as the Peer 

Consultation Group (PCG) as per the MOU.) 

As required by MOU Section V.E .2 .m., EPA provided further input to DuPont in a letter dated 

September 24, 2009 from Jim 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 from the PCG as summarized in the final Meeting Report and to the input received 

from EPA. As EPA agreed "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") of the Final Report. 

General Response 

DuPont commends Dr. Small and the PCG members for their thorough and thoughtful review of 

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 the Charge. 

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 if possible, are highly relevant when considering Phase III activities . None of these factors were 

envisioned when the MOU was signed in 2005, but they are highly relevant and must be considered when 

determining what Phase III work 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 PCG recommendations to address those particular data 

needs. 

Scope of 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?" Our work was based on a reasonably literal 

interpretation of these guidelines . 

From EPA guidelines : 

"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 and assumptions, may be 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 EPA or other agency-approved work plan . 
The guidelines further state: 

"Exposure assessments may use measured data or model estimates. Representative measured 

data of known quality are preferred over model estimates and are 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 of the 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, and our confidence 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 

EPA Guidelines for Exposure Assessment state: 

"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 outcome of the 

assessment. . . . . A common 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 . " 

Accordingly, based on the EPA Guidelines, 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, nor was the ultimate product of the work to be a health-based risk assessment of 

the local community, although that is certainly occurring by other means (see below). 

It is noted that some members of the PCG differed with this interpretation of the 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 noted in Section 2 of the Final Report : 

"It should be noted that members of the panel did differ in their understanding and expectations 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, with full coverage of potential migration and exposure pathways . Others interpreted 

the term "screening" to imply that a somewhat more initial assessment was intended, which would 

then encompass a more-limited sampling and evaluation of a more-limited set of pathways. " 

The DuPont Phase II Scope of Work and SLEA are very 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 of Other 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 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 considered the adequacy of the media dataset. 

(2) Mitigation of Exposure 

Subsequent to the signing of the MOU, certain actions have already occurred, or are underway, to 

mitigate or reduce exposure of the local community and environment. Given that the objective of the MOU 

was to determine pathways of PFOA exposure to guide development of ways to reduce exposure, then the 

following major initiatives begun since the MOU was signed are highly relevant to whether additional 

Phase III data collection are additive : 

Emission Reductions--Washington Works PFOA manufacturing emissions to air, water, 

and land have been reduced by 99% since 2000 through aggressive programs as part of or 

preceding adoption of the US EPA 2010/15 PFOA Stewardship Program by 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 achieve this 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 GAC filtration 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 

to significantly reduce PFOA in discharges from these sites. 

(3) Relevant Data Obtained through other 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 of University of Pennsylvania) 

or by the C-8 Science Panel formed as part of the Leach settlement. 

Universitv of Pennsylvania-Emmett Studies 

Dr. Emmett and his team examined 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 testing 
for PFOA blood serum levels. His study determined that drinking water was the primary route of exposure 

for this community. The study also 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 serum levels and drinking water exposure of approximately 100:1 . The results of the study 

were published (Emmett et 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 of Hygiene and Tropical Medicine 

" David Savitz, PhD, Mount Sinai School of Medicine 

" 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 from over 

70,000 local residents from the communities around the Site . The studies include (with currently scheduled 

completion dates) : 

" CARDIOVASCULAR RISK FACTORS MEASURED IN THE BLOOD 2008 

" THE CANCER IMMUNE FUNCTION, LIVER, AND HORMONE 2009 

DISORDERS STUDY BASED ON C8 HEALTH PROJECT 

" THE COMMUNITY FOLLOW-UP STUDY 2011 

" THE WORKER FOLLOW-UP STUDY 2011 

" THE STUDY OF BIRTH OUTCOMES IN THE WHOLE COMMUNITY 2009 

" THE STUDY OF BIRTH OUTCOMES AMONG C8 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 from these 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 now complete and 

notification of publication has been made by the journal Epidemiology, Shin et al., 2009. Retrospective 

Exposure Assessment Estimation for Perfuorooctanoic Acid in Eastern Ohio and Western West Virginia. 

In a symposium abstract 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 water for nearby residents, is 

now the main route of exposure. Contamination of public 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 of groundwater will continue for 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 belief that 

additional Phase III sampling under the MOU, beyond that already defined in the FDNA, is likely to be 

redundant or of limited value. 

Section-By-Section Response to PCG Feedback 

3.7 .1 . Comprehensive Air Monitoring 

Comment from PCG: 

"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 few mile radius of the site and 

possibly beyond. " 

Response to the PCG Comment: 

Several publications confirm that 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 few miles from the site, as 

shown in Figure 5.7 of the DAR. Current and future air emissions from the Site are not anticipated to 

contribute significantly to drinking water levels given that air emissions have been reduced 99% since 

2000. 

Comment from PCG (continuedl 

"Although DuPont reports a substantial (two-order-of-magnitude) decrease in air emissions by 

2006, the amount of PFOA actually being emitted now or in the past is not reported. " 

Response to the PCG Comment: 

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 500 pounds, 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 ammonium pertluorooctanoate will eliminate PFOA air emissions from the site, removing any 

impact to groundwater from ongoing air emissions at the Site. 

Comment from PCG (c ontinued): 

"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 PCG in 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 and deposition 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 the spatial extent of the Site influence. Air sampling should be 

extended to distances (horizontally) where the influence of local sources disappears and PFOA levels 

representative of atmospheric background levels are seen. This strategically holistic data set will not only 

quantify current emissions and exposure, but when coupled with a mass balance modeling approach (see 

Section 3.7.6 below), will enable the estimation of environmental loadings and exposures associated with 

historic emissions. " 

Response to the PCG Comment: 

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 not further inform future 

exposure potential. 

(1) Current emissions of PFOA and its presence in environmental media are well understood 

Air emissions from manufacturing 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 . Stack testing 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 from point sources. It is also notable that by 2015, or sooner 

if possible, complete phase-out will eliminate PFOA air emissions from the site . 

The presence of PFOA in environmental media as a result of air 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 the environment, and what concentrations are present that may result 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 from the 

site . 

(3) Additional efforts to research air concentrations do not further inform future 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 if possible, is impractical and 

does not further inform the potential for exposure in the study population . 
p. 10 . 

3.7.2 Spatially Extensive Surface Water Monitoring 

Comment from PCG: 

`A spatially comprehensive synoptic survey ofPFOA concentrations in the Ohio River is needed 

to characterize the spatial extent and source-receptor relationships of water quality impacts from the Site. " 

Response to the PCG Comment: 

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 the spatial extent of PFOA in the environment generally. 

Surface water data from the 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 from the 

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 of the screening level exposure assessment . 

Source-receptor Relationship of Water Oualitv Imnacts from the Site 

With regard to characterizing the source-receptor relationship of water quality impacts from the 

Site, we feel that it is already well characterized . Section 3.2 .1 of the SLEA describes the exposure 

pathways evaluated in the human exposure assessment and identifies surface water as a secondary source of 

PFOA. Section 3.2 .2 of the SLEA describes 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 medium were 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 from manufacturing 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 from incidental ingestion of surface water was 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 serum levels 

from dermal exposure to surface water were estimated to be an additional three orders of magnitude lower 

still. 

Bearing in mind that these de-minimis exposures from contact with surface water were based on 

pre-emissions reduction surface water data, it follows that any exposure assessment conducted using postemissions reduction data would only show even lower levels of exposure . We therefore believe that 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 "of trivial importance" and do not merit additional study. 
p. 11 

Comment from PCG (continued): 

"Given the small number of randomly collected Ohio River water samples 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 time period when actual releases are occurring at 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 running perpendicular to the bank), and 

should extend downstream as far as possible, but in any case should include areas known to have drinking 

water contamination (e.g. at least as far downstream as Crab Creek or -90 miles) Water samples and 

attendant sample concentrations should be constructed to yield quantifiable PFOA concentrations in all 

surface water samples. " 

Response to the PCG Comment: 

As stated above, the purpose of this investigation program was not to delineate the extent 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 downstream of the Site would be significantly less 

than originally reported in the DAR as a result of emissions reduction measures at the Site . 

Comment from PCG (continued) : 

"A few creeks and shallow water bodies (e.g., Brinker Run for Letart Landfill and Lee Creek for Dry Run Landfill) that,Jlow through the landfills and sediments in these creeks should also be analyzed, as 

these creeks are conduits for PFOA to the Ohio River. High concentrations of PFOA are possible in these 

creek waters and sediments. Coincident fish, sediment and water samples as part of the synoptic water 

quality survey (sic). " 

Resnonse to the PCG Comment: 

We believe that analyzing water and sediments from creeks and shallow water 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 from PCG: 

"Bottom sediment samples need to be obtained from the Ohio River in areas immediately adjacent to Washington Works outfalls, upstream, and downstream, as well as downstream of the landfill sites. Transects should be designed to capture the extent of PFOA contamination related to a specific outfall and should include differential depth analysis. " 

Resnonse to the PCG Comment: 

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 from surface 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 equilibrium conditions between the river water and 

the river sediments. However, a river such as the Ohio tends to have some amount of sediment scouring 

and transport, thus tending to further reduce the concentration of PFOA expected to be present in sediments 

in the vicinity of the Site. Given the predicted low levels 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 

of the Screening Level Exposure Assessment. 

Comment from PCG (continued): 

"A related need is to sample a sediment transect running from the Site across the river to the 

LHWA. This transect would be designed to detect the existence of any seepage zones emanating from the 

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 Digestion ponds pre andlor post installment of an engineered cap system, to thoroughly examine 

this potential PFOA transport pathway. " 

Response to the PCG Comment: 

DuPont does not believe that groundwater emanating from the RBL seepage zones, if they existed, 

could migrate to LHWA well field. Perched groundwater within 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 A of 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 

aquifer where groundwater flow is 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 river water and flow downstream 

with the river water. Given the flow in the river and the distance from the Site to the LHWA well field, 

there is no scientific basis to believe that PFOA seeps, if any, would overcome the downstream current and 

disperse across the river to the LHWA well field. 

In addition, the continuous pumping of production wells on both sides of the Ohio River produces 

a groundwater divide under the Ohio River, with water on the north side of the river flowing through the 

river bottom recharging the LHWA well field, and with 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 and the former Anaerobic Digestion 

Ponds would be able to overcome the ground 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. from PCG: 

"Pump and tracer tests are needed to further explore possible hydraulic connections between the 

Ohio River waters near the Site and groundwaters on both sides of the river. These are needed to support 

assessments of the potential for off-site transport scenarios that may occur with changes in pumping of the 

Ranney Well, the DuPont-Lubeck Well Field, or the East Well Field, and whether or not pumping at LHWA 

induces any unexpected hydraulic connection between the groundwater associated with the Anaerobic 

Digestion ponds and waters that eventually enter the LHWA well field. " 
p. 13 

Response to the PCG Comment: 

Pump and Tracer Tests 

DuPont does not believe that conducting pump tests, tracer tests, or the options suggested by the 

PCG described in Section 3 .7 .4 would provide significant additional understanding of the groundwater flow 

between the DuPont Site and the LHWA. As stated above, the groundwater divide under the Ohio River 

does not allow for groundwater from the site to migrate to the LHWA well field. 

Field measurements of groundwater elevation data from the Site and LHWA show that river water 

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 flow pathway 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 A of 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 aquifer where groundwater flow is 

towards the Ranney Well (Figure 3.8 of the DAR). 

As stated previously, if this 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 and flow downstream with the river water. Given the flow in the river and the distance from the 

Site to the LHWA well field, there is no scientific basis for concern that this PFOA would disperse across 

the river to the LHWA well field. 

Once groundwater reaches the underlying aquifer, the groundwater divide under the river (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 from migrating off -site, with the 

exception of some limited off-site groundwater migration that may be 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 14A of the Appendix 3.2 of the 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 of the 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 from PCG (continued): 

"Modeling in agreement with previously reported data from the USGS for 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) and what appears to be increases in PFOA concentrations in the water being pumped out by the 

LHWA. The latter may be due to only contributions from wet/dry deposition and run off down the west 

slope of deposited PFOA; however, sufficient uncertainty warrants further 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 Expansion of the Groundwater Flow Model for the Site 

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 of the groundwater flow model for the Site and surrounding area (discussed below), 

including LHWA, and in the development of the site conceptual model that describes the sources and 

transport pathways from on-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 flow model for the DuPont Washington Works Site in 

1999 (DuPont RFI, 1999). In 2002, DuPont revised and expanded the groundwater flow model with the 

following objectives : 

" to address comments made by USEPA and the U.S . Army Corps of Engineers (ACOE) on the 

original model 

" to address comments from the members of the C-8 Groundwater Investigation Steering Team 

(GIST) that was established by the Order on 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 under various pumping scenarios. 

Data Utilized for the Revised Groundwater Flow Model 

Included in the revision and expansion of the DuPont groundwater flow model was general data 

for the Ohio River such as : 

" Lithology, thickness and depositional history of the Ohio River alluvial sediments 

" Historical low water levels of the Ohio River 

" Terrace ages and elevation. 

In addition to these general data listed above, site-specific data for the areas encompassed within the model 

were obtained from West Virginia Geological Survey publications, RFI reports submitted to regulatory 

agencies from DuPont 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 from DuPont. These 

site-specific data types included: 

" well and soil borings 

" lithologic descriptions 

" groundwater elevation measurements, including two rounds of synoptic groundwater levels 

" aquifer testing results 

" aquifer hydraulic conductivity data 

" grain size analysis results 

" estimated recharge rates 

" daily, and in some cases hourly, pumping rate data. 

The model revision and expansion work included input from experts at the USEPA, the ACOE, 

and the USGS and from the 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 of the 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 between the model predicted results and the actual field measurements. 

Simulated Groundwater 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 of the former GE Site), and 

" No LHWA pumping 

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 needs for the public water systems and manufacturing activities 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 14A of the 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 of the PCG Final Report, the existence of this groundwater 

divide is in agreement with published data from the 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, 

Kozar and McCoy note no discernible differences between the 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 flow to 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 from LHWA to 

potentially flow to 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 

from the 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 the alluvial aquifer and the Ohio River. Groundwater flow in the 

bedrock aquifer from LHWA 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 flow model, 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 form prepared for the Washington Works site . The "Yes" determination on the form submitted by 

DuPont indicates that migration of contaminated groundwater is under control at the Site . On April 23, 

13 
2004, 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 groundwater flow model, 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 of the model. This synoptic surveying will be conducted in 2010 under the Site RCRA Facility Investigation (RFI) activities . 

PCG Pronosed 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 of the granulated 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 MOU Progress 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 flow within the LHWA or the DuPont 

alluvial aquifers, nor would this data have a meaningful impact on the screening level exposure assessment . 

Comment from PCG (continued): 

"Further, tracer tests should be used to delineate potential pathways between the LHWA and the 

former-ADP area in/under the river bed. These pumping and tracer studies should significantly reduce the 

uncertainty associated with these potential groundwater-river water pathways . " 

Response to the PCG Comment: 

As discussed in our first response to the PCG comment for Section 3 .7 .4, we do not believe that 

conducting pump tests, tracer tests, or the options suggested by the PCG described in Section 3.7 .4 will 

provide significant additional understanding of groundwater flow between the DuPont Site and the LHWA. 

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 . 

3.7 .5. Additional Biological Monitoring 

General Comment from PCG: 

"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, locally produced meat, fish from surface 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 and characterization, such as household dust or water distribution systems downstream 

of centralized water treatment. " 

14 
p. 17 

General ResQonse to the PCG Comment: 

The SLEA acknowledged the inherent uncertainty present in virtually every exposure assessment, 

including itself. Some of these uncertainties stem from a 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 of chemical 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 a consideration of the adequacy of the media dataset. 

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 outcome of the assessment. A common 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 "of trivial 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 MOU specified that : "The Screening Level Exposure Assessment 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. " 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 of the various subpopulations for which the 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 PCG Final 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 from an individual 

farm pond would inform the question of whether the few individuals 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 exposures to 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 

media will, either directly or as a surrogate for other related media, inform the question of significance of a 

number of potential 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 from the SLEA, 

as a means to further demonstrate the degree of understanding of the relationship between environmental 

levels of PFOA and community exposures. We also include brief discussions of the relative significance of 

the contributions from some of the non-drinking water pathways in the relevant sections, below. 

15 
Specific Resnonses to Specific Elements of the PCG Gomment: 

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 from their 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 Locally Produced Meat 

The PCG comments recommend the collection of locally-produced meat to understand whether 

consumption of such 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 areas where exposure via drinking water is lowest . In that 

context, it is useful to develop data that can help to inform the question of whether or not meat ingestion is 

a potentially significant source of human exposure . 

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 from the analysis of locally-produced milk in conjunction with the 

pharmacokinetic expressions that describe the relationships between milk and meat, the milk-PFOA data 

can serve as a surrogate for 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 EPA to develop an approach for better understanding meat 

ingestion as a potential source of exposure. 

Sampling Fish from Surface Waters 

As described in the DAR, the fish sampling program collected target fish from two locations in the 

Ohio River - downstream of Site Outfa11005, and approximately 26 miles upstream of the Site . The 

objective of the program was to determine the 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 of possible bioaccumulation, as well as bottomdwelling fish that may accumulate chemicals through direct contact or through the ingestion of benthic 

invertebrates, detritus, or small fish associated with the benthos. 

Based on this information, the following species were targeted for sampling: 

" Largemouth bass (Micropterus salmoides) 

" Channel catfish (Ictalurus punctatus) 

Three tissue types were analyzed for PFOA from each fish sample: 

" Fillets 

" Viscera, including the liver 

" Carcass 

16 
The area immediately below Outfall 005 represented a portion of the river that potentially received 

PFOA from the Site ; thus, fish collected from this 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 from the Site, and 2) it contains similar habitat as the area downstream of Outfa11005 . 

The summary data indicate that, with the exception of viscera from catfish 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 

whether consumption of 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 inform the question of whether or not fish ingestion is a significant source of PFOA exposure 

for persons living in the vicinity of the 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 from fish 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 local water bodies, such as farm ponds 

or lakes would experience a greater level of PFOA exposure than fish living immediately downstream of 

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 for fishing, and not for evaluating exposure at a sub-population level. 

PBPK modeling using the calculated external doses of PFOA from fish ingestion was used to 

estimate the range of internal doses of PFOA that may result from fish 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 of fish 

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 not warranted. 

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 from populations living in the vicinity 

of the Site were not available, the potential for infant exposure via ingestion of breast milk was evaluated in 

the SLEA. This was accomplished using information on local serum levels of PFOA provided in Emmett 

et al. (2006) and data obtained from a review of the scientific literature regarding PFOA in 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 from 45 women in Massachusetts was approximately 1% of 

the mean reported PFOA concentration in serum from female U.S . blood donors in the 2003-2004 National 

Health and Nutrition Examination Survey (NHANES), corresponding to a breast milk/serum ratio 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 from Tao 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 of the Site, given the extensive degree to which PFOA serum levels have been studied there. 

The PCG comments recommend the collection of breast milk samples to understand whether 

consumption of breast milk could represent a potentially significant source of exposure to PFOA to nursing 

infants. 

Based on the established pharmacokinetic relationships between drinking water, serum and breast 

milk levels of PFOA, it does not appear to be necessary to collect breast milk in order to determine whether 

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, and consumed 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 from ingestion 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 seem to 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 from the 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 meadow vole (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 LHWA property is known to 

have occurred. 

Data from both liver and blood plasma from voles collected at LHWA showed 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 voles were 

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 inform the 

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 of game animals. 

CoordinatinQ Ex1uosures 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 and the design 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 from the SLEA for all of the major exposure pathways was assembled. Then, 

using the PBPK relationship from Clewell (2009) serum PFOA levels that would be expected to result from 

these external exposures were calculated . This analysis is presented in Table 1 . 

As shown in Table 1, the predicted MTE level of PFOA in human serum from the ingestion of 

drinking water in the Little Hocking service district using external exposures from the SLEA is 490 ug/1 . 

This value aligns very well with the 221-576 ug/1 interquatrile range (mean = 448 ug/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 of exposure 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 

from the ingestion of locally-produced milk and crops by farmers and gardeners, respectively, predicts 

PFOA serum levels 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 of Multimedia Model to Evaluate PFOA Mass Balance in Nearby 

Environment 

Comment from PCG: 

"A multimedia mass balance modeling approach should be used to synthesize the available 

information on PFOA mass flow and 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 and exposure 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, and to identift and define future data collection needs. " 

Response to the PCG Comment: 

The recommended mass balance model has been developed for the Washington Works community 

covering the years 1951 to 2003 and was published in 2007 by Paustenbach et al. Historical emissions 

from the facility were used in conjunction with various well-accepted environmental 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 PFOA used 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 show that the sum of the total mass of PFOA in each 

of the compartments equals the total amount of APFO used at the plant for each year. " 

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 the facility . 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 model would 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 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 PCG recommendations to address those data needs. 

Phase III Work Plan Outline 

1 .0 Introduction 

2.0 Data Analysis and Reporting 

2.1 Method Development and Validation 

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 of the 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 of Locally Produced Milk- Within 1-Mile of Dry Run 

and Letart Landfills 

7.0 Schedule and Reporting 
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DuPont, 2009d. Letter from D. F. Altman (DuPont) to Raymond S. Franks (WVDEP), regarding Quarterly Air Emissions reporting from 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., Desai, C, Shaw, L.M. . 2006. Community exposure to perfluorooctanoate : relationships between serum concentrations and exposure sources. J. Occup. Environ. Med. 48(8), 759-770. 

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Steenland, K, Fletcher, T, Savitz, D., 2008. Status report: Factors associated with PFOA in a community 

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Tao, L, Kannan, K, Wong, CM, Arcaro, K.F ., Butenhoff, J.L. . 2008. Perfluorinated compounds in human 

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Fromme, H. . 2008. Perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) in human 

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Managment. West Virginia Consent Order No. GW-2001-019 
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