p. 1 

March 3, 2010 

Andrew S. Hartten 

Project Director 

DuPont Corporate Remediation Group 

Barley Mill Plaza - Bldg . 19 

4417 Lancaster Pike 

Wilmington, DE 19805 

-._a 

Attn: Memorandum of Understanding (MOU) between the U .S . Environmental 

Protection Agency (EPA) and E. I . DuPont de Nemours and Company (DuPont) 

for a Perfluorooctanoic Acid (PFOA) EPA Comments on DuPont's Responses to 

the Peer Consultation Panel's Input on the Outline of Phase II Work Plan 

Dear Mr. Hartten : 

This letter is submitted pursuant to Sections V.E.2.m of the above-identified 

MOU and includes EPA's Comments on DuPont's Responses to the Peer Consultation 

Panel's Input on the Outline of Phase II Work Plan dated December 18, 2009. EPA 

has carefully reviewed DuPont's December 18, 2009 response and EPA agrees with 

the Peer Consultation Group (PCG) that additional monitoring data are needed to fully 

address the "Charge" as defined in the MOU. EPA's review of the Final Report of the 

Peer Consultation Group, dated July 15, 2009, identified a number of significant issues. 

These issues relate primarily to DuPont's interpretation of concepts within the Charge 

and DuPont's willingness to conduct further sampling to better define releases and 

exposures according to the language of the Charge. This summary highlights the major 

topics of importance that are explained in detail in the attached comments . 

The Charge as defined in the MOU does not limit exposure to "on and around 

the site" but states that "pathways of migration and exposure associated with the site" 

are to be characterized and assessed . The term "Associated with the Site" as defined 

in the MOU does not limit Phase III data collection to only characterizing exposure on 

and around the site but specifically includes characterizing those exposures associated 

with the site regardless of distance from the site. 

EPA does not agree that the Screening Level Exposure Assessment developed 

by DuPont under the MOU generated screening level estimates of exposure which fully 

addresses the Charge . Because of the limited spatial extent of the monitoring data 

D~r_~~G-oi~~ 

UNITED STATES ENVIRONMENT"qWTION~AGENCY 

WASHINGTON p.Ct,' 2046A~ 4 ~ 

f tj ~,`-~~i\ -c3 +~,~~ t0' 37 OFFICE OF 

PREVENTION, PESTICIDES, AND 

TOXIC SUBSTANCES 

CONTAINS NO CBI ,~S ~-3~-1 % 0 
collected to date, it is not possible to estimate exposures to populations further away 

from the site, even at a screening level . 

The Ohio River is a major drinking water source downstream from the site. The 

limited spatial extent of the data that DuPont generated do not allow an understanding 

of how the concentration in the river varies with distance, or how the levels of PFOA in 

river water used as a drinking water source downstream vary. EPA believes that this 

potential pathway of exposure needs to be understood at a screening level in order to 

fully address the Charge. 

EPA believes that additional sampling is needed for environmental media on and 

around the site as well as associated with the site to fully address the Charge. The 

available data are not sufficient to determine the spatial extent of the releases and 

PFOA exposures at a screening level for air, sediments, ground water, surface water, 

biota, locally grown produce, milk, meat, game animals and sludge and solid waste 

generated by the site. 

EPA does not agree with DuPont's conclusion that "there is a high degree of 

certainty that the exposure potential associated with the site has already been 

characterized" . EPA does acknowledge that other work such as that of the C-8 Science 

Panel, Emmett, and others will inform the characterization of the site, but believes that 

additional monitoring is needed beyond what DuPont recommends in order to fully meet 

the Charge as defined in the MOU. Detailed comments are attached. 

lis"D1Irector 

cal Control Division 7405M) 

cc: EPA Docket ID No . : OPPT-2004-0113 

Cathy Fehrenbacher - Mail Code 7406M 

Lawrence Libelo - Mail Code 7406M 

David W. Boothe 

E. I . du Pont de Nemours and Company 

4417 Lancaster Pike, CRP 708/110 

Wilmington, DE 19805 
EPA Comments on DuPont's December 18, 2009 Response to the Peer 

Consultation Panel's Input on the Outline of Phase II Work Plan Pursuant to 

the Memorandum of Understanding (MOU) Between USEPA and DuPont 

Company 

Introduction 

EPA agrees with DuPont that the goal of the November, 2005 MOU between EPA and 

DuPont is stated by the language of the Charge as written below: 

Are current PFOA environmental releases and sources of 

environmental releases from the Site and the presence of PFOA 

in environmental media on and around the Site sufficiently 

understood so that pathways of migration and exposure to PFOA 

associated with that Site are adequately characterized and 

assessed on a screening level basis? 

In addition, EPA and DuPont agreed to language in Section V.A.2 .a .,b .,c ., and d 

of the MOU which establishes the general scope of the PFOA Site-Related 

Environmental Assessment Program and governs interpretation of the Charge. EPA will 

use this language in interpreting the Charge as pertains to the MOU. For example, as 

stated in MOU Section V.A.2 .a., "Associated with the Site," is further defined as 

including " . . .all activities that may have resulted in the current presence of PFOA in 

environmental media both on and off the site without regard to distance from the site . . ." 

In addition, Section V.A.2.c further defines "Pathways of Migration" as referring to the 

" . . . routes by which PFOA moves from any Current or Past Manufacturing Activity 

through Environmental Media, and includes but is not limited to, leaching to surface 

water or groundwater from land-applied materials; discharge from areas with 

contaminated groundwater to surface waters or wells; releases from landfills to air, 

groundwater and surface water; and air deposition to soils and migration to 

groundwater." The terms "Environmental media" and "Exposure to PFOA Associated 

With The Site" are also further defined in the MOU. 

Selected comments are presented below from the PCG Report that further 

clarify the Agency's comments regarding additional data for the Phase II I Future 

Data Needs Assessment (FDNA) . In keeping with the MOU, the Agency believes 

that additional characterization and monitoring is needed to fully address the 

Charge, in the context of the MOU definition of the Screening Level Exposure 

Assessment . 

Impact of Other Relevant Factors on Phase III Scope 

The MOU was signed in 2005, and as DuPont notes, new information has 

been discovered about PFOA exposures in the Parkersburg, West Virginia area 

since that time . The revised Screening Level Exposure Assessment (SLEA) should 

include relevant scientifically credible information collected concerning these 

exposures. DuPont cites the work by Emmett and the C-8 Science Panel . The 
Agency is familiar with these data and analyses. 

EPA does not completely agree with the three factors that DuPont has 

chosen to take into consideration as relevant for Phase III work. The Charge does 

not limit exposure to "on and around the site" but states that "pathways of migration 

and exposure associated with the site" are to be characterized and assessed . As 

stated above, the term "Associated with the Site" is further defined in the MOU. 

DuPont should not limit Phase III data collection to only characterize exposure on 

and around the site but instead should characterize those exposures associated 

with the site regardless of distance from the site, in keeping with the Charge. 

To fully address the Charge, collection of additional data are needed to 

understand sources, pathways exposures to humans and the environment at a 

screening level . 

Scope of Work Considerations- "Screening Level Basis" 

DuPont has also provided additional information on a screening level exposure 

assessment in its comments of December 18, 2009 . EPA notes that Section V.D.3. of 

the MOU defines the term "Screening Level Exposure Assessment" . The MOU states 

that the Screening Level Exposure Assessment (SLEA) " . . .shall characterize exposure 

and releases associated with the Site in accordance with EPA's "Guidelines for 

Exposure Assessment". . ." and use the scenario evaluation approach set forth in the 

Guidelines. The MOU further states that the SLEA for current human exposure " . . .will 

include a quantitative, conservative assessment for any exposure pathway for which 

the data allow quantitative assessment. Where the data do not allow such quantitative 

assessment of an exposure pathway, the Screening Level Exposure Assessment for 

current human exposure will present a qualitative or semi-quantitative description of 

exposure." Finally, the MOU states that although the SLEA will ". . . focus primarily on 

current human exposure, it will characterize the presence of PFOA in environmental 

media, including biota, on and off the site as a result of current or past manufacturing 

activities." EPA will use the language in Section V.D.3 in interpreting the term 

"Screening Level Exposure Assessment" as used in the MOU. 

Collecting sufficient data to support an adequate characterization of 

environmental releases and sources of PFOA, and characterization of the pathways 

of migration for PFOA are necessary prerequisites to enabling an adequate 

Screening Level Exposure Assessment, as defined in the MOU. This is one of the 

main points that the Peer Consultation Group (PCG) makes throughout their Report. 

EPA strongly agrees with the PCG on this point. 

EPA does not agree that the Screening Level Exposure Assessment 

developed by DuPont under the MOU generated adequate estimates of exposure. 

For some pathways and subpopulations close to the site, the SLEA may be 

adequate, but for some near to the site, and all further from the site, the SLEA is not 

adequate to fully address the Charge . Because of the limited spatial extent of the 

monitoring data collected to date, it is not possible to estimate exposures to 

populations further away from the site, even at a screening level, unless some very 
conservative assumptions are made. For example, there is no clear indication of a 

decreasing trend of PFOA concentrations in environmental media based on the 

monitoring data which has been collected under the MOU. Thus, a screening level 

exposure assessment using the available data would conservatively assume that 

exposures further away from the area sampled were comparable to those in the 

area sampled . EPA does not agree that the SLEA generated "more realistic central 

estimates of exposure" for populations beyond the extent of the monitored area. 

Mitigation of Exposure 

EPA agrees with DuPont that a great deal of additional information has been 

generated since the MOU was signed and that this information should be included in 

developing Phase III . EPA also agrees that DuPont has undertaken significant 

actions to substantially reduce releases from the site. In keeping with the Charge, 

the Phase III monitoring should include sufficient data to characterize current and 

future exposures at a screening level. Recent data on environmental 

concentrations, such as the increasing concentrations in groundwater at the Little 

Hocking Well Field (Hartten, 2010), suggest that the response of environmental 

concentrations to the reductions in air and surface water emissions is not a simple 

linear process . Understanding if the environmental concentration are decreasing as 

a result of reduced emissions or increasing because of residual PFOA in some 

environmental compartments requires ongoing monitoring . While ongoing 

monitoring is beyond the scope of the MOU, until and unless it can be shown that 

concentrations in environmental media are decreasing it is not valid to say that 

exposures are decreasing. For a screening level assessment, one should expect to 

err on the side of being protective, and assume that concentrations are not 

decreasing, in the absence of data. 

DuPont offers descriptions of three types of actions which have been taken 

that are believed to be highly relevant to whether or not Phase III data collection is 

required for the drinking water pathway. These three actions are: 1) Washington 

Works reduction of PFOA manufacturing emissions to air, water, and land by 99% 

since 2000; 2) DuPont phase out of PFOA manufacturing by 2015 at the latest ; and 

3) DuPont providing granular activated water treatment to all public and private 

water districts containing PFOA at or above the site-specific EPA Action Level of 0.5 

ppb and Provisional Health Advisory of 0.4 ppb . EPA recognizes the value of the 

actions DuPont has taken to address drinking water exposures on and around the 

Washington Works site. However, as stated previously and in the comments below, 

these actions are not sufficient to relieve DuPont of further data collection in Phase 

III to fully address the Charge . 

In their review of additional information that has been generated since the 

MOU was signed, DuPont has made several incorrect statements or interpretations . 

Emmett et al did not measure exposure . They did not "quantify total 

exposure" rather they measured levels in human tissue. They were not able to 

quantify historical exposure, especially for the air pathway exposure . 
The C-8 Science Panel Exposure Assessment Study is not complete. The C8 Science Panel has been constrained in their ability to correlate effects of PFOA 

with exposure because of the lack of sufficient data. Modeling is being used to try 

to estimate current and past exposures . This work in ongoing and the reference 

DuPont cites is a meeting presentation abstract of initial modeling estimations . 

The C-8 Science Panel modeling suggests that groundwater concentrations 

are increasing despite reductions in emissions, and that it will take decades for 

concentrations to begin to decrease . This is in agreement with the limited ongoing 

data from the Little Hocking wells and shows that more monitoring is needed to 

adequately characterize current and future exposures. 

DuPont states that PFOA use will be eliminated by voluntary phase out. 

However, the Charge addresses exposures resulting from Current and Past 

Manufacturing Practices, as stated above. The SLEA should address exposures 

resulting from current and past manufacturing practices in keeping with the Charge. 

Air Monitoring 

Monitoring data submitted by DuPont under the MOU has documented soil 

and ground water contamination well beyond the boundary of the available air 

measurements . EPA believes that the available data are not sufficient to determine 

the spatial extent of the exposure at a screening level, and it is not possible to 

characterize and assess exposure sufficiently at a screening level for populations 

further away from the site. EPA agrees that the highest exposures are probably 

occurring close to the site but does not agree that sufficient data exists to 

characterize exposure to people further from the site. In the absence of other data, 

a conservative (protective) screening level assumption would be that individuals 

further from the site may be exposed at similar concentrations . 

Spatial Extent of Surface Water Monitoring 

In response to several PCG recommendations, DuPont states that 

understanding the spatial extent of the PFOA contamination associated with the site 

is not significant, and that conducting sampling to delineate the extent of the 

contamination further from the site "would not have a meaningful impact on the 

results of the screening level exposure assessment". EPA believes that the spatial 

extent is significant and that the suggested additional monitoring data are needed to 

adequately evaluate exposure further from the site at a screening level . The 

distribution of PFOA on and around the site (spatial as well as temporal) determines 

the breadth of the data collection required for adequate screening level 

characterization of releases, sources and migration pathways and subsequent 

exposure assessment. 

The MOU states that the Charge includes characterization, at a screening level, 

of exposures associated with the site regardless of distance . In keeping with this 

language, EPA interprets the Charge to include all exposures associated with the site, 
not only those in close proximity to the site. As stated above, the Charge includes " . . .all 

activities that may have resulted in the current presence of PFOA in environmental 

media both on and off the site without regard to distance from the site. . ." The 

screening level exposure assessment should not be limited to only the highest 

exposure levels close to the site. 

For example, the Ohio River is a major drinking water source downstream 

from the site. DuPont data shows elevated PFOA levels in the river at the 

downstream limit of sampling . The limited spatial extent of the data that DuPont 

generated does not allow a sufficient understanding of releases from the site and 

presence of PFOA in the river . Therefore, the pathway of migration from the site 

and exposure to PFOA from use of river water as a source of drinking water 

downstream from the facility cannot be adequately characterized and assessed on a 

screening level basis. Greater then 2 million people use the Ohio River as a source 

of drinking water downstream from the site, and potential exposure to PFOA 

associated with the site is not known . EPA believes that this potential pathway of 

exposure needs to be understood at a screening level in order to fully address the 

Charge and that the currently available data are not sufficient . 

DuPont's states in paragraph 2 on page 8 of the December 18, 2009 

Response that 

"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." 

DuPont added the last phrase in the sentence above: "not to characterize the 

spatial extent of PFOA in the environment generally." This phrase was not included 

in the MOU. The MOU does not limit the spatial extent of the exposure to be 

characterized or assessed . The Agency is aware of additional data, including that 

generated by the Cincinnati Water Works, that show elevated PFOA levels a 

considerable distance downstream of the site . 

EPA agrees with the PCG Report that additional surface water monitoring of 

the Ohio River downstream of the Washington Works site should be conducted . 

This should include an evaluation of direct seepage and tests to better understand 

the hydraulic flow to and beneath the river . Based on the insufficient 

characterization of Ohio River surface water listed below and on page 8 of the PCG 

Report, the Agency agrees that additional data are required . 

" Ohio River sampling . . . intermittent, and lacking in information regarding time of 

day or week, plant operation, river flow etc. . . . difficult to interpret what the 

reported river concentrations mean. 

" Adequate explanation . . .not provided for absence of detectable PFOA in river 

samples along transects near the site, given the presence of PFOA in Ohio 

River. . . in drinking water intake samples many miles downstream. 
" Water samples at the Washington Works outfalls and landfill leachate water 

samples suggest these locations could have provided potentially important 

routes of PFOA transport to groundwater and the Ohio River. 

" No water samples collected from other surface water bodies; neither in the 

study area nor in any stream or river sediments PFOA in these media could 

lead to exposure to biota and subsequently through the human food chain. 

Groundwater concentrations in wells in the Little Hocking well field are 

increasing and do not appear to have reached a plateau or started to 

decline(Hartten, 2010) . Groundwater recharge to the Ohio River is a major source 

of water input and may be delivering PFOA to the river . As the levels of PFOA in 

the groundwater increase over time the amount discharged to the river will also 

increase. EPA does not agree with DuPont's suggestion that additional surface 

water data are not needed because emissions have been greatly reduced. As 

stated above, the Charge clearly includes exposures resulting from Current and 

Past Manufacturing Activities at the site . Without additional data it is not possible to 

determine the effect of the emission reductions on water concentrations and 

associated exposures or to support the assertion that levels are declining . 

EPA agrees with the PCG recommendations that additional sampling from 

creeks and shallow water bodies is needed for a screening level characterization in 

order to fully address the Charge . These are a source of input to the Ohio River as 

well as possible direct exposure pathways and need to be characterized . 

River Sediment Monitoring 

DuPont's December 18, 2009 Response regarding sediment monitoring 

addresses a very narrow scope concerning sediments. DuPont has only considered 

direct contact of fishermen and swimmers to sediments and has not looked at the 

bigger role of sediments as the migration pathway for PFOA from sources like the 

Riverbank landfill and the Aerobic Digestion Ponds to sediments and then on to the 

Ohio River and drinking water downstream . This is a major point in understanding 

the migration and exposure pathways. EPA agrees with the PCG suggestion in the 

Report that the collection of more data and better characterization of sediments, 

surface water and groundwater is needed at a screening level . The PCG Report 

contains these points on pages 59 and 60 . 

" Bottom sediment samples need to be attained from the Ohio River in areas 

immediately adjacent to Washington Works outfalls, upstream, and 

downstream as well as downstream of landfill sites. 

" Transects should be designed to capture extent of PFOA contamination 

related to a specific outfall and include differential depth analysis. A related 

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

to the LHWA . . . designed to detect the existence of any seepage zones 

emanating from the Riverbank Landfill that could potentially have released 

PFOA that migrates to the LHWA . 
Groundwater Pump and Tracer Test 

DuPont asserts that conducting pump tests, tracer tests or other options 

suggested by the PCG would not provide significant additional understanding of the 

groundwater flow between the DuPont site and Little Hocking Water Authority 

(LHWA) . However, DuPont has not, as the PCG Report points out, provided a 

proper validation of the groundwater model on which they rely for the statement that 

no further groundwater data are needed. High concentrations of PFOA observed in 

wells immediately north of the aerobic digestion ponds after removal of material and 

what appear to be increases in PFOA concentrations in LHWA wells raise questions 

about the adequacy of the data on PFOA in groundwater near the plant boundary 

and understanding pathways of migration to the river and beyond . EPA agrees with 

the PCG recommendation that additional screening level data are needed . 

DuPont believes that the flow patterns are greatly controlled by pumping on 

both sides of the river . As the PCG report describes on page 32, this is not 

substantiated . EPA agrees with the PCG that additional data are needed to clarify 

understanding of the hydrogeology and PFOA transport in groundwater at a 

screening level . 

The PCG Report contains the following data collection recommendations on 

page 60. 

" Pump and Tracer tests. . . needed to further explore possible hydraulic 

connections between the Ohio River waters near the Site and ground 

waters 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 and the DuPontLubeck 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. 

" Modeling in agreement with previously reported data from the USGS of 

the Parkersburg region indicates a groundwater divide under the Ohio 

River. . . however, this modeling effort is in need of further validation . . . 

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. 

Additional Biological Monitoring 

EPA agrees with the PCG recommendations that additional screening level 

biota sampling is needed . Data are also needed on plant products. Because of the 

widespread soil and water contamination, EPA believes that all crops grown in the 

area are exposed to soil and may be watered with contaminated groundwater or 

surface water. Based on available data (Stahl, 2009), plants readily take up and 
concentrate PFOA, and the levels in crops need to be measured to estimate 

screening level exposure to the local population and to others that may consume 

crops grown in the area . Until the extent of the contamination is determined it is not 

possible to adequately evaluate exposure by this pathway. Limiting Phase III to 

within several miles from the site will not allow evaluation of the exposure via 

consuming contaminated crops further from the site, unless one assumes, as a 

conservative, screening level assumption, that contamination levels in crops are the 

same as those measured closer to the site . Crops grown on soil further from the 

site may be contaminated and the extent and levels of PFOA contamination are 

needed to conduct a screening level exposure assessment. 

Sampling Farm Produce and Locally Produced Meat 

DuPont states on page 16 of their response to the PCG Report 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 that could be ingesting locally grown crops as a smaller 

portion of their daily intake of these foodstuffs. EPA does not agree that garden 

vegetables are a reliable surrogate for commercial crops. Data collected by DuPont 

and 3M have shown that different plant species take up PFOA at different extents . 

Stahl, et al. 2009, reported that bioaccumulation of PFOA in corn straw is hundreds 

to thousands of times greater then in ears. Bioaccumulation factors in grains (e.g ., 

oats and wheat factors range from one hundred to several thousand) suggest that 

these crops may be a significant uptake and exposure pathway to humans and nonhuman species (Stahl, et al, 2009) . DuPont has proposed in the FDNA to sample 

locally grown crops and produce only within 2 miles of the site and optionally milk 

within 1 mile of the Letart Run Landfill. EPA believes that commercial crops, milk, 

and home grown produce outside the 2 mile radius also need to be sampled. 

DuPont bases their interpretation of needed data on the belief that local gardeners 

and farmers are likely to be the most highly exposed population . Based on available 

soil and groundwater concentrations, EPA does not agree that it is possible to 

determine that the most highly exposed population is within 2 miles . Soil and 

groundwater levels at and beyond the two mile radius are not significantly lower then 

those within 2 miles. EPA believes that sampling is need to better understand the 

extent of the contamination or to document a downward trend in concentrations at 

specific distances from the site before any assessment of the highest exposures can 

be made. 

Based on the available monitoring data associated with the site, soil and 

groundwater contamination could result in crops in the area taking up PFOA. There 

is potential for exposure from consumption of plant items grown on contaminated 

soil and watered with contaminated water. If the contamination in the area is wide 

spread, the potential for wide spread exposure is possible. The exposure to PFOA 

by this pathway needs to be understood in order to fully address the Charge 

The monitoring proposed by DuPont in Phase III does not adequately 

respond to the PCG Report recommendation for addressing human exposure to 

PFOA through farm produce and locally produced meat. The PCG Report 
addresses the PFOA migration pathway from drinking water to livestock and 

groundwater/surface water irrigation to crops by local farms. Collection of data in 

actual locations where PFOA has migrated from water through the crops to the 

humans and from the water into the crops and livestock would enable DuPont to 

fully address the Charge . Fields in the Parkersburg, WV area with PFOA in the soils 

and water are the best locations for data collection for characterizing these 

exposures at a screening level . The PCG Report has the following comments on this 

topic on pages 39 and 40 . 

" Although DuPont reports have argued that airborne deposition has been 

the only source of PFOA to crops and crop products, studies have 

documented that PFOA is efficiently transferred from contaminated soil to 

crops (Stahl et al., 2009). Feeding of livestock with fodder and other crops 

grown on PFOA contaminated soils can result in food chain transfer of 

PFOA in and around the site and the landfill areas. 

" According to US EPA, approximately 37% of households in the South 

have home gardens. Model exposure analysis has indicated that 

consumption of locally grown crops, meat products, and milk could 

contribute exposures similar in magnitude to intakes of PFOA of attained 

via ingestion of drinking water. 

" There is a need to determine concentrations of PFOA in homegrown 

vegetables and fruits, locally grown farm produce, milk and meat. . . not 

only for homes located within a two-mile radius of the site but also for the 

farms along the Ohio River. Data for biota from the Dry Run Landfill and 

the Letart landfill are needed to accurately assess exposures in these 

locations. 

Sa mpling Game Animals : 

DuPont's approach of using the results of rodent data to predict that other 

animals will not be contaminated is not valid . Data from other contaminated areas 

has shown that deer and other wild game animals take up PFOA from consumption 

of contaminated vegetation, soil and water 

(http ://www.epa .gov/region4/water/PFCdaltonindex .html) . Extrapolation from voles 

to predict that other wild and domestic animals do not accumulate PFOA is not valid . 

Additional sampling of game animals is needed to fully address the Charge. 

Multimedia Fate, Transport, and Exposure Pathways 

This section of the report addresses multimedia transport of PFOA from 

release to exposure and provides specific details on why pathways of migration and 

exposures need to be characterized with appropriate and sufficient data to fully 

address the Charge . EPA agrees with the conclusions and recommendations of the 

PCG . Report statements on pages 44- 47. 

For the pathways of migration from release to exposure to be adequately 

characterized on the screening level basis, we expect the following to be 
satisfied. - 

1 . The major pathways of migration from the source to exposure media 

should be identified. 

2. A basic understanding of the processes governing this migration and the 

major factors influencing these processes should be demonstrated. 

3. A semi quantitative description of the mass flows along the major 

pathways of migration from the source to exposure media should be 

presented. 

4. Sufficient field data should be presented to demonstrate that the basic 

understanding of the major processes and the semi quantitative mass flow 

calculations are roughly consistent with the reality in the study area. 

Further, the PCG report summarizes and concludes: 

1 . The site conceptual mode! adequately describes many of the transport 

pathways to people living close to the source. However neither the 

exposure to PFOA nor the pathways of migration for people living more 

distant from the plant are characterized. This deficit is judged to be 

particular serious for the population exposed via river water downstream 

of the site. 

2. The site conceptual model appears to be factually incorrect in its 

placement of the SWMU and its correct location, on the rim of the river. 

The conceptual model also omits a potential transport pathway from this 

SWMU into the Ohio River and a pathway into groundwater that may also 

flow away from the site. 

3. . . . several intermedia pathways of migration of PFOA are not yet 

understood at the basic level. Deficits exist particularly regarding the 

transport of PFOA from surface soil to groundwater, and from air and 

water to food. 

4. A semi quantitative description of the mass flows along some partial 

pathways of migration is presented (for example from air to surface soil). 

However, no assessment along the entire major pathways (air-surface 

soil-groundwater-drinking water) is provided. 

5. Data were collected and assessed to evaluate atmospheric transport and 

deposition to soil following emissions to air at the Washington Works site. 

Data were also collected in surface water, but no effort was made to 

assess the relationship between emissions to surface water and transport 

via surface water. Measurements were conducted that supported the 

understanding of the relationship between atmospheric emissions and 

deposition to terrestrial surfaces, but no effort was identified that 

evaluated quantitative understanding of the link between atmospheric 

emissions and the levels in groundwater from the unsaturated or 

saturated zones. Measurements to assess the transfer of the PFOA from 

air and water to are fully absent. 

6. There is very poor understanding of the transfer from groundwater to food. 
7. The transfer of PFOA from the atmosphere to grass is not sufficiently 

understood. . . consequently the transport from the atmosphere into food is 

also not understood. 

8. No measurements have been done on pathways leading to food. This is 

appropriately identified as a future data need in the reports. 

Human Exposures 

DuPont did not respond to the PCG comments about human exposures. 

There are a number of important points in the human exposures section of the PCG 

Report that the Agency supports. The following points are excerpted from pages 56 

through 57 of the Report. 

" Except for possibly drinking water, a screening exposure analysis does not 

appear to represent the local community "situations" since most of the data . . . 

used are from other locations it would not be representative of any of the 

three sites. 

" . . . exposure analysis receptor scenarios selection . . . has not provided 

information on the actual local behaviors of the population that supports the 

selected activities . 

" The EPCs for PFOA found in food are based on deposition in uptake models. 

Local data on PFOA in homegrown and locally raised foods are necessary, 

and consumption practices for local foods need detailed evaluation for use in 

exposure assessment. 

" The RME and MTE estimations use many assumptions that are not valid or 

justified for the local situation. Further, no effort has been made to tie the 

screening results to a known acute or chronic health outcome. What do the 

values for the RME or MTE mean in terms of potential health effects? There 

is no health slope factor or reference dose provided for comparison with data 

available from other locations where health effects have been demonstrated 

after exposures to PFOA have been identified. 

" The Washington Works Facility and Local Landfill should be the focus of any 

immediate revision for screening characterization since there are actual data 

available. Concurrently the data needs must be thoroughly discussed and 

weaknesses removed with a better PFOA data collection . 

" Any revisions to the Dry Run Landfill, and the Letart Landfill screening 

exposure characterization must include a logical plan for data collection . . . 

" The screening exposure assessment should be forward-looking in 

perspective and utilize the extensive biomonitoring data in the population that 

now receives the drinking water through the Little Hocking Water Association, 

other public systems and from private wells. The biomonitoring data should 

offer insights regarding the variability in exposures. Conceptual model for 

exposure needs to consider additional sampling based upon the recently 

established emissions from the stacks, and develop air and biota monitoring 

programs that can achieve the goals of a revamped program. 
Disposal of Sludge and Solid Waste 

EPA notes that disposal of sludge and solid wastes generated at the Washington 

Works plant have occurred on and off the site (Ritchey, 2006) . Evaluation of off-site 

disposal locations and resulting exposures are being addressed through other 

mechanisms by relevant state and federal agencies . To the extent that exposures from 

these activities are not addressed by other state and federal agencies activities, Phase 

III monitoring needs to include sufficient data collection to allow a screening level 

evaluation of the exposure at these off site locations. 

Information provided to West Virginia by DuPont suggests that some 

contaminated solid wastes were deposited on-site (Ritchey, 2006). Additional Phase III 

sampling is needed to characterize, at a screening level, the residual PFOA in the East 

Field, Chestnut farm and other areas which may have received PFOA containing waste, 

and to quantify transport from these areas to the river and groundwater. 

References 

Peer Consultation Panel, 2009. 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, July 15, 2009 . 

Hartten, Andrew S., 2010. Little Hocking Water Association APFO and PFOA 

Analytical Results - Granulated Activated Carbon Treatment System December 

2009 Biweekly Sampling Event #2, 4Q09 Annual Sampling Event, and 1Q10 

Backwash Sampling . Letter to Robert Griffin dated February 16, 2010 . 

Ritchey, Robert L., 2006 . Letter from to Cliff D . Whyte, WVDEP dated July 12, 

2006. Docket # EPA-HQ-OPPT-2003-0012-1098 . 

Stahl, T. et al . 2009. Carryover of perfluorooctanoic acid (PFOA) and 

perfluorooctanesulfonate (PFOS) from soil to plants. Arch . Environ . Contam. 

Toxicol. (in press, available online) .