DEQ-CFW_00001577

Recommended Water and Soil Screening Levels for Perfluorooctanoic Acid (PFOA
or C8)
1. Summary
Water and soil screening levels have been developed for PFOA as follows:
Recommended PFOA Water screening level = 0.0021 mg/L or 2.1 µg/L
Recommended PFOA Soil screening level to protect groundwater as a drinking water
source = 2.2 mg/kg
Recommended residential soil level for adult = 157 mg/kg
Recommended residential soil level for child = 18 mg/kg
Recommended industrial soil level = 185 mg/kg
Basis for levels: RfD = 0.0003 mg/kg-day; Critical endpoints = Reduction in mean body weight
and body weight gain from F, male rat pups and F, adult male rats (Ft generation from Fo adult
rats) and increased liver weights in Fo parental males; Critical study = Two generation rat gavage
study by York et al., 2002 and Butenhoff et al., 2004.
2. Background
The chemical name for C8 is Perfluorooctanoic acid (PFOA). It has a CAS number of
335-67-1 and a molecular formula of C8HF1502.One of its salts, ammonium
perfluorooctanoate (APFO; C8171502NH4; CAS No. 3825-26-1) is the compound that is
the most widely used in industry and most of the animal toxicology studies have been
carried out with this compound. Once absorbed in the body, APFO disassociates to the
PFOA anion.
3. Basis for Screening Levels
The first step in developing water and soil screening levels for PFOA involves
determining whether the levels should be based on the carcinogenic or noncarcinogenic
effects of the chemical. If the screening levels are based on carcinogenic effects, then the
chemical is assumed to not exhibit a threshold and a risk approach is used to develop the
basis for the screening levels. In the risk approach, a study (usually animal but can be
human) that examined carcinogenic effects is selected to be the basis for the assessment.
Mathematical models are used to determine a cancer slope factor based on the results
seen in the study. A cancer slope factor is an upper -bound estimate of risk per increment
of dose. From the cancer slope factor, unit risk estimates are developed. Unit risk
estimates convert the cancer slope factor to units of drinking water (µmg/L) or air (µg/3).
From the unit risk, risk -specific doses can be derived that estimate the dose associated
with a specific risk level, for example, a one -in -a -million (1 x 10-6) increased lifetime
risk.
If the screening levels are based on noncarcinogenic effects, then the chemical is assumed
to exhibit a threshold and a Reference Dose (RfD) is developed. The RfD is an estimate
(with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the
DEQ-CFW 00001577

human population (including sensitive subgroups) that is likely to be without an
appreciable risk of deleterious effects during a lifetime. The RED is calculated to be
protective against a critical effect, which also results in protection against other effects at
higher doses. The RED is expressed in units of mg/kg (body weight) -day.
Epidemiological studies in workers have not seen an increase in cancer from exposure to
PFOA. Two animal carcinogenicity studies have been carried out. One study reported
increases in Leydig cell adenomas and mammary gland fibroadenomas. The second study
reported increases in tumors in the liver, Leydig cells, and pancreas. EPA's draft risk
assessment on PFOA (EPA, 2005a) concluded "overall, based on no adequate human
studies and uncertain human relevance of the tumor triad (liver, Leydig cell and
pancreatic cell tumors) from the rat studies, PFOA may be best described as "suggestive
evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential"
under the draft 1999 Guidelines for Carcinogen Risk Assessment."
EPA's SAB submitted a report on January 20, 2006 on EPA's draft risk assessment. In
this report, they stated that the majority of panel members concluded that the
experimental weight of evidence with respect to the carcinogenicity of PFOA was
stronger than proposed in the draft document, and suggested that PFOA is a "likely"
carcinogen in humans. This was based on the following:
• While human data is ambiguous, two animal studies have shown carcinogenic
effects at several sites.
• There exist too many uncertainties in the mode of action for liver tumors to say
that they are not relevant to humans.
• Mammary gland adenocarcinomas seen in the animal study should be considered
related to PFOA treatment.
• Insufficient data are available to determine the mode of action for the Leydig
cell, pancreatic, and mammary gland tumors, and thus they must be presumed to
be relevant to humans.
A few members of the SAB did not find the weight of evidence sufficient to support the
"likely" descriptor and agreed with the EPA's conclusion that PFOA showed suggestive
evidence of carcinogenicity. This was based on the opinion that the mode of action for
the liver tumors was not relevant to humans and that the mammary gland tumors were not
demonstrated in animals when compared to historical controls.
The following are the key reasons why the West Virginia Assessment of Toxicity Team
for PFOA (CATT) did not conclude that the animal carcinogenicity data indicates that
PFOA is probably carcinogenic in humans:
• PFOA has not been shown to be genotoxic. Genotoxic compounds bind to DNA
and are more likely to be carcinogenic than nongenotoxic compounds. Although
nongenotoxic compounds can be carcinogenic, they are usually much weaker
carcinogens that pose a lesser risk to human health.
• The liver tumors seen in the animals were probably caused by a mechanism of
action that is not relevant in humans.
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• The Leydig cell tumors are rarely seen in humans and the mechanism of action
appears to be non -linear.
• Technical questions on whether the mammary gland adenocarcinomas and
pancreatic tumors were related to the PFOA treatment.
Since EPA has not classified PFOA as a probable human carcinogen, they have not
calculated a cancer slope factor for the chemical. The West Virginia CATT concluded
that they would base their water and soil screening levels on the noncarcinogenic
endpoints of PFOA (the RfD). They stated that they believed that the RfD would be
protective against the possibility of liver tumors and Leydig cell tumors, since these
tumors, if shown to be relevant to humans, would operate under a nongenotoxic, non-
linear mechanism (WV DEP, 2002). The EPA Guidelines for Carcinogen Risk
Assessment state that, "For cases where the tumors arise through a nonlinear mode of
action, an oral Reference Dose or inhalation Reference Concentration should be
developed in accordance with EPA's established practice. This approach expands the past
focus of such reference values (previously reserved for effects other than cancer) to
include carcinogenic effects determined to have a nonlinear mode of action" (EPA,
2005b).
Based on the reasons outlined in the above paragraph, the water and soil screening levels
for PFOA have been calculated based on the RfD of 0.0003 mg/kg-day considering
noncarcinogenic effects. According to Dr. Luanne Williams, a toxicologist with the North
Carolina Department of Health and Human Services, there is some uncertainty in using
the chronic oral reference dose of 0.0003 mg/kg-day for calculating groundwater and soil
screening levels for PFOA. There is uncertainty associated with the reference dose of
0.0003 mg/kg-day because of the serious critical data gaps in the carcinogenicity and
toxicity of PFOA (Williams L, 2006).
4. RfD Development
An RfD is calculated as follows:
• Review available human and animal studies on the chemical
• Weigh studies for applicability to be used as the critical study for RfD
determination. Some of the determining factors are:
o Length of study
o Number of animals used
o Endpoints examined
o Relevance of route of exposure
o Quality of study (follows EPA or other guidelines)
o Exposure levels defined (often a problem in epidemiology studies)
o Critical effect determined
• Determine critical study
• Determine highest dose level at which a critical adverse effect does not occur
(NOAEL) or the lowest dose level at which a critical adverse effect does occur
(LOAEL) from the critical study
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Determine appropriate uncertainty factor (UF) to be applied to the NOAEL or
LOAEL
• Divide NOAEL or LOAEL by UF.
Table 1 presents a summary of the studies that were considered for RfD derivation. The
human studies were determined to be inadequate for RfD determination (all studies
reviewed and summarized in EPA, 2005a and West Virginia DEP, 2002).
Tahle 1 _ Studies Considered for RfD Derivation
Study
Animal (sex)
Length
Doses
NOAEL
LOAEL
Effects
(route)
(mg/kg-day)
(mg/kg-
(mg/kg-
for APFO
day)
day)
and PFOA
as indicated
Thomford et
Cynomolgus
26 weeks
0, 3, 10, 30
ND
3
Increased
al, 2001
monkey (M)
(oral capsule)
APFO
liver weights,
possible
mortality
Goldenthal,
Rhesus
13 weeks
0, 3, 10, 30,
ND
3
Clinical signs
1978b
monkey
(gavage)
100 PFOA
(M,F)
Goldenthal,
CD rats
13 weeks
0, 0.56, 1.72,
1978a
(M)
(diet)
5.64, 17.9,
0.56
1.72
Increased
63.5 PFOA
liver weights
(F)
0, 0.74, 2.3,
7.7, 22.4,
22.4
76.5
Increased
76.5 PFOA
liver weights
Palazzolo,
ChR-CD rats
13 weeks
0, 0.06, 0.64,
0.06
0.64
Increased
1993; Perkins
(M)
(diet)
1.94, 6.50
liver weights,
et al., 2004
APFO
liver
hypertrophy
Sibinski,1987
Sprague-
2 years (diet)
Dawley rats
(M)
0, 1.3, 14.2
1.3
14.2
Increased
liver weights,
1.6, 16.1
liver
(F)
APFO
1.6
16.1
hypertrophy
Decreased
body
weights,
effects on
blood
Cook et al.,
Sprague
2 years (diet)
0, 14.2 NR*
ND
14.2
Increased
1994
Dawley rats
liver weights
(M,F)
Riker
Rats
2 years (diet)
Laboratories,
(M)
0, 1.3, 14
1.3
14
Increased
1983
0, 1.6, 16
liver weights
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(F)
NR*
ND
1.6
Ovarian
hyperplasia
York et al.,
Sprague-
2-generation
0, 1, 3, 10, 30
ND
1
Increased
2002;
Dawley rats
reproductive
APFO
liver weight
Butenhoff et
(M, F)
study
**
al., 2004
(gavage)
ND
1
Significant
reduction in
mean body
weight gain
ND
1
Decreased
body weight
and body
weight gain
Gortner, 1981
Sprague
GD 6-15
0, 0.05, 1.5,
150
ND
No effects
Dawley rats
5, 150 APFO
(M, F)
Staples, 1984
Sprague-
GD 6-15
0, 100 APFO
100
ND
No effects
Dawley rats
(M,F)
Gortner, 1982
New Zealand
GD 6-18
0, 1.5, 5, 50
5
50
Development
white rabbits
APFO
al effects,
such as extra
rib
* NR = compound (APFO or PFOA) not reported
**Effect noted in Fo parental males (shown on page 72 of EPA 2005a). However, a mode of action analysis has
demonstrated that the liver effects on rats are due to a peroxisome proliferator-activated receptor alpha or PPAR a
—agonism. According to EPA, this mode of action is unlikely to occur in humans (shown on page 8 of EPA
2005a).
***Effect noted in Fl male pups (pups from Fo adult rats) (shown on page 68 of EPA 2005a).
****Effect noted in FI adult males (pups from Fo adult rats) (shown on page 73 of EPA 2005a).
GD = gestational day
ND = not determined since effects were seen at all doses tested
APFO = Ammonum perfluorooctanoate
PFOA = Perfluorooctanoic acid
York et al., 2002; Butenhoff et al., 2004 was selected as the critical study for the
derivation of the RfD. The reasons for this include the fact that the study:
• Is of excellent quality
• Follows EPA OPPTS guidelines for conducting reproductive/developmental
studies
• Examined for multiple organ effects as well as developmental effects from two
rat generations.
• Presents the lowest LOAEL of all the chronic and developmental studies (the only
study with a lower LOAEL (0.64 mg/kg-day) Palazzolo, 1993; Perkins et al. 2004
is only 13 weeks duration).
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Table 2 presents the study and factors used to calculate the RfD for PFOA:
Table 2. RfD for PFOA
Study
Critical
Effect
NOAEL
LOAEL
OF
JIM
York et al.
Reduction in
NOAEL was
1 mg/kg-
3,000
0.0003
2002;
mean body
not
day APFO
mg/kg-day*
Butenhoff et
weight and
determined
al. 2004
body weight
since effects
gain from F,
were seen at
male rat pups
all doses
and F, male
tested.
adults
*According to Dr. Luanne Williams, a toxicologist with the North Carolina Department
of Health and Human Services, the 1 mg/kg-day LOAEL for APFO could be used with
some caution to derive a chronic oral reference dose of 0.0003 mg/kg-day for calculating
groundwater and soil screening levels for PFOA. There is uncertainty associated with the
reference dose of 0.0003 mg/kg-day because of the serious critical data gaps in the
carcinogenicity and toxicity of PFOA (Williams L, 2006).
A total uncertainty factor (UF) of 3,000 (UF = UFH (10) x UFA (10) x UFs (1) x UFL (10)
x UFD (3) = 3,000) was used, consisting of the following areas of uncertainty:
1. Intraspecies variability (UFH). This factor accounts for the natural differences that
occur between human subpopulations and for the fact that some individuals may
be more sensitive than the average population. EPA recommends values of 3-10
for this factor. UFH = 10 because have not defined the most sensitive
subpopulation for C8.
2. Interspecies variability (UFA). This factor is used to account for differences in
response between animals and humans. EPA recommends values of 1-10 for this
factor. UFA = 10 because no data available on quantitative differences between
animals and humans in pharmacokinetics of C8.
3. Subchronic to Chronic Extrapolation (UFs). This factor is applied when the
database lacks information on the health effects of the chemical following lifetime
exposure. EPA recommends values of 1-10 for this factor. UFs = 1 because many
chronic studies available on C8.
3. LOAEL to NOAEL Extrapolation (UFL). This factor is applied when
extrapolating from a LOAEL to a NOAEL. UFL =10 since a LOAEL (reduction
in mean body weight gain) was used in the calculations.
4. Database (UFD). This factor is applied when there are significant data gaps on the
chemical. EPA recommends values of 1-10 for this factor. UFD = 3 since there are
database gaps on the toxicity of PFOA.
5. Water Screening Level
A water screening level is derived from the multiplication of the RfD by the assumed
body weight of an adult and divided by the assumed daily water consumption of an adult.
This value is then multiplied by a relative source contribution to take into account
DEQ-CFW 00001582

exposures from other sources i.e., the relative source contribution (RSC). The RSC is
assumed to be 20% for organic chemicals and 10% for inorganic chemicals. The
following equation is used (NC, 2005a):
Water Screening Level for PFOA = RfD x BW x RSC
DI
Where: RfD = RfD PFOA = 0.0003 mg/kg-day
BW = Body weight of an adult, default = 70 kg
RSC = Relative source contribution, default = 20% for organics
DI = Daily water intake for an adult, default = 2 L/day
Water Screening Level for PFOA
= 0.0003 mg/kg-day x 70 kg x 0.20 = 0.0021 mg/L = 2.1 µg/L
2 L/day
6. Soil Screening Level protective of groundwater
A soil screening level protective of groundwater is derived by multiplying the acceptable
groundwater concentration by a soil/water partitioning equation. This equation relates
concentrations of contaminants adsorbed to soil organic carbon to soil leachate
concentrations in the zone of contamination. This is then multiplied by a dilution factor,
which corresponds to the reduction in contaminant concentration, from the contaminated
soil, to the groundwater. The following equation is used (NC, 2005b):
Soil Screening Level = Cgw[ks + QW + O H' ] Df
[ Pb ]
Where: Cgw = Groundwater target concentration, PFOA = 0.0021 mg/L (water
screening level, calculated above)
ks = Soil -water partition coefficient, PFOA = 52 L/kg (Prevedouros et al.,
in press)
OW = Water -filled soil porosity-vadose soil, default = 0.3 LWater/Lso,j
Oa = Air -filled soil porosity-vadose soil, default = 0.13 Lair/Lso;l
Pb = Dry bulk density, default =1.5 kg/L
H' = Henry's Law Constant x conversion factor of 41, PFOA = 1 x 10-11 x
41 = 4.1 x 10-10 (West Virginia DEP, 2002)
Df= Dilution factor, default = 20
Soil Screening Level for PFOA = 0.0021 mg/L [52 L/kg + 0.3 + (0.13) (4.1 x I Of)120 =
1.5
2.2 mg/kg
7. Residential and Industrial Soil Screening Levels
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IM
Recommended residential and industrial soil levels were calculated based on EPA Region
9's background technical document for Preliminary Remediation Goals (PRGs) (EPA,
2004). For both residential and industrial soil levels, only ingestion and dermal
absorption were considered as routes of exposure. EPA indicates volatilization for water
or soil should only be evaluated for chemicals with Henry's Law constants greater than
10-5 and molecular weights less than 200. Since PFOA's Henry's Law constant is 10-11
and its molecular weight is 431, volatilization was not evaluated.
Residential soil level:
mg/kg = THQ x AT x BW
EF x ED x [(1/Rf) x Soil IR) + (1/RfD x SA x AF x ABS )l
106 106
Where:
THQ = Target Hazard Quotient, assumed to be 1
RfD = The oral Reference Dose for C8 = 0.0003 mg/kg-day
BW = Body weight, assumed to be 70 kg for adults and 15 kg for children
AT = Averaging time, 10,950 days for adults (365 days/year x 30 years), 2,190
days for child (365 days x 6 years)
EF = Exposure Frequency, 350 days/year, the average number of days each year
people are exposed
ED = Exposure duration, 30 years for adults, 6 years for child, the average
number of years people are exposed
Soil IR = Ingestion rate for soil = 100 mg/day for adults, 200 mg/day for children
SA = Surface area of exposed skin, 5,700 cm. 2/day for adult, 2800 cm2/day for
child
AF = Adherence factor, 0.07 mg/cm2 for adult, 0.2 mg/cm2 for child, the amount
of soil that adheres to skin
ABS = Skin absorption factor, specific factor not available for C8, assumed to be
0.1 for semi -volatile chemical per EPA guidance
Residential soil level for adult:
1 x 10,950 x 70
350 x 30 x [(1/0.0003 x 100) + (1/0.0003 x 5,700 x 0.07 x 0.1 )]
106 106
= 156.5 mg/kg =157 mg/kg
Residential soil level for child:
DEQ-CFW 00001584

I x 2,190 x 15
350 x 6 x [(1/0.0003 x 200) + (1/0.0003 x 2,800 x 0.2 x 0.1 )]
106 106
= 18.3 mg/kg = 18 mg/kg
Industrial soil level:
mg/kg = THQ x AT x BW
EF x ED x [(1/RfD x Soil IR) + (1/PJD x (SA x AF x ABS)]
106 106
Where:
THQ = Target Hazard Quotient, assumed to be 1
RfD = The oral Reference Dose for C8 = 0.0003 mg/kg-day
BW = Body weight, assumed to be 70 kg for adults
AT = Averaging time, 9,125 days (365 days/year x 25 years)
EF = Exposure Frequency, 250 days/year, the average number of days each year
people are exposed
ED = Exposure duration, 25 years, the average number of years people are
exposed
Soil IR = Ingestion rate for soil = 100 mg/day for adult worker
SA = Surface area of exposed skin, 3,300 cm2/day for adult worker
AF = Adherence factor, 0.2 for adult worker, the amount of soil that adheres to
skin
ABS = Skin absorption factor, specific factor not available for C8, assumed to be
0.1 for semi -volatile chemical per EPA guidance
Industrial soil level:
1 x 9,125 x 70
250 x 25 x [(1/0.0003 x 100 + (1/0.0003 x 3,300 x 0.2 x 0.1)]
106 106
= 184.7 mg/kg = 185 mg/kg
8. References
EPA, 2005a. Draft Risk Assessment of the Potential Human Health Effects Associated
with Exposure to Perfluorooctanoic acid and its Salts. Office of Pollution Prevention and
Toxics, Risk Assessment Division. SAB Review Draft.
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EPA, 2005b. Guidelines for Carcinogen Risk Assessment. Risk Assessment Forum,
Washington, DC. EPA/630/P-03/001F.
EPA, 2004. Users Guide and Background Technical Document for USEPA Region 9's
Preliminary Remediation Goals (PRG) Table.
North Carolina Department of Environment and Natural Resources, 2005a.
Classifications and Water Quality Standards Applicable to the Groundwaters of North
Carolina. Subchapter 2L. Division of Water Quality.
North Carolina Department of Environment and Natural Resources, 2005b. Guidelines
for Establishing Remediation Goals at RCRA Hazardous Waste Sites. Division of Waste
Management, Hazardous Waste Section.
Prevedouros K. et al., in press. Sources, Fate and Transport of Perfluorocarboxylates.
Environmental Science and Technology.
West Virginia Department of Environmental Protection, 2002. Final Ammonium
Perfluorooctanoate (C8) Assessment of Toxicity Team (CATT) Report.
Williams L, 2006. Dr. Luanne K. Williams, Toxicologist with the North Carolina
Department of Health and Human Services.
DEQ-CFW 00001586

4 - w
Ammonium Perfluorooctanoate (C-8
EPA OPPT Draft Risk Assessment Jan. 2005 : This risk assessment did not calculate
RfD, RfC, or cancer slope factors. Calculated a number of margin of exposures (MOEs) -
the ratio of the NOAEL or LOAEL for a specific endpoint to the estimated human
exposure level. Based estimated human exposure levels on serum levels of C8 from.
human biomonitoring studies.
Cancer: "Suggestive evidence of carcinogenicity, but not sufficient to assess human
carcinogenicity."
EPA's SAB (Feb 2005)• Reviewed EPA's Draft Risk Assessment — A draft report is
available (June 2005), but no final report. The majority of panel members concluded that
the experimental weight of evidence with respect to the carcinogenicity of C-8 was
stronger than in the draft document and suggested that C-8 is a "likely carcinogen in
humans." However, they would not calculate a slope factor for C-8.
West Virginia: M 2002, West Virginia prepared a C-8 Assessment of Toxicity Team
(CATT) Report, resulting from a consent decree between the WV Environmental
Protection Agency and Du Pont as a result of finding C-8 in Lubeck, WV. This report
used a team of 10 expert toxicologists from TERA (a non-profit consulting firm) to
determine human health provisional risk factors for the oral and inhalation routes of
exposure and calculated risk -based human health protective screening levels (SLs) based
on EPA Region 9's standard methodology. This report summarizes all the relevant
studies and the methodology used to develop the following numbers:
• RfD: 0.004 mg/kg-day (based on York, 2002 two -generation
reproductive/developmental study in rats, used a benchmark dose level of 0.42
mg/kg-day divided by an uncertainty factor of 100).
• RfC: 1 µg/m3 (based on Kennedy et al., 1986 2-week inhalation study in rats,
used a benchmark concentration level of 0.33 mg/m3 divided by an uncertainty
factor of 300).
• Cancer assessment: An oral cancer slope factor of 0.31 per mg/kg-day was
developed for Leydig cell tumors, however the panel agreed that the RfD
should be the basis for the water and soil screening levels since they had low
confidence in the cancer value, high confidence in the RfD, and felt that the
RfD would be protective against the possible cancer effects (liver tumors) in
humans.
• SL (water): 150 ppb (p.34 of CATT report for equation used)
• SL (soil): 240 ppb (p.34 of CATT report for equation used)
• SL (air): 1 µg/m3 (p.34 of CATT report for equation used)
Minnesota: 3M produced C-8 and other perfluorochemicals at Cottage Grove, MN from
the late 1940s until 2002. The facility was used for a variety of industrial operations and
also includes a permitted hazardous waste incinerator. The Minnesota Pollution Control
Agency has been overseeing the site and entered into a consent decree with 3M in 1985
requesting that they conduct environmental monitoring and other activities. 3M found
groundwater contaminated with C-8 and also conducted medical monitoring of its
DEQ-CFW 00001587

employees. In 2002, the Minnesota Dept. of Health developed a Health -Based Value
(HBV) for drinking water and a Soil Reference Value (SRV) for C-8 as follows:
• HBV (drinking water) = 7 ppb (based on RfD of 0.001 mg/kg-day from
Thomford et al. 2001, 26 week study in monkeys showed liver effects, p.3 of
MDH memo for equation used to calculate HBV)
• Residential SRV = 30 mg/kg; Industrial SRV = 200 mg/kg (based on RfD of
0.001 mg/kg-day (as above), RfC of 2E-5 mg/m3 (based on 3 M generic
exposure guidelines for chemicals found to be carcinogenic in animals but with
unknown relevance to humans) and dermal absorption of 10% (Minnesota's
default for organic compounds). They did not present the equations they used to
derive the SRVs from the RfD, RfC, and dermal absorption factor.
In 2005, an ATSDR health consultation was prepared for the Minnesota Dept. of Health
at the Cottage Grove site. This health consultation summarized the available exposure
and health information on C-8, as well as the HBV of 7 ppb and SRV values. The
summary of this report states that the potential health impacts from C-8 releases cannot
be fully assessed at this time and additional investigation is needed.
Ohio: Ohio EPA has posted a letter on their website stating that C-8 was detected in some
water supplies in Ohio and cited the West Virginia preliminary action level of 150 ppb.
They stated that they are relying on the U.S. EPA to study C-8. They also stated that all
their detections of C-8 were below the West Virginia action level; however DuPont has
agreed to finance a program to provide bottled water to customers of the water system
that had the highest levels of C-8 detected.
New Jersey: No information was given on the New Jersey web site about C-8.
DEQ-CFW 00001588

More on Ammonium Perfluorooctanoate (C-8)
The Environmental Working Group (EWG): I have reviewed the EWG's criticisms of the
West Virginia C-8 numbers. Their concerns are as follows:
• They believe that the West Virginia RfD does not contain an adequate safety
factor. They obtained a preliminary draft of provisional RfDs and Screening
Levels done by West Virginia that EWP posted on their website. In this draft, a
different study and a much larger safety factor were used in the calculations than
that used in the final RfD. The EWG does not take issue with the different.study
or the basic safety factor used in the final RfD; their criticism centers on the fact
that in the calculations of the provisional RfD, an additional safety factor (called
a modifying factor) of 3 was applied to the RfD because C-8 has a long half-life
and the potential to bioaccumulate in humans. The EWP says that this additional
factor of 3 should have been applied, resulting in an allowable level of C-8 in
drinking water of 50 ppb, not 150 ppb.
Response: In December, 2002, EPA's Risk Assessment Forum completed its
"Review of the Reference Dose and Reference Concentration Processes" and the
panel recommended that the use of the modifying factor be discontinued, since
the purpose of the modifying factor is covered by the other uncertainty factors.
Thus, I do not believe that this criticism by the EWG is valid at this time.
They state that West Virginia ignored substantial background exposure from
contamination in air and food. They cite EPA's standard assumption that 20% of
a contaminant comes from drinking water and 80% comes from other sources,
and they state that had West Virginia used this assumption the allowable amount
of C8 in tap water would be 30 ppb, instead of 150 ppb.
Response: This is not an easy issue. It is true that, in the absence of better data,
EPA's Office of Water uses a standard assumption that 20% of a contaminant
comes from drinking water and 80% from other sources, in developing their
drinking water health advisories and other health levels. Also, Minnesota used a
20% source contribution from drinking water in their calculation of the Ground
water health -based value (HBV) from the RfD. However, West Virginia based
their water screening level on EPA Region 9 guidance on deriving risk based
concentrations which used a different equation that did not factor in a 20% source
contribution. I have not been able to verify this guidance. I have searched EPA's
website and cannot find this guidance posted; however I have e-mailed the
consulting firm that was responsible for preparing West Virginia's guidance and
hopefully they will be able to direct me to it. However, at this point, I would.
agree with the EWG that 20% is generally used by the EPA in these types of
calculations.
• Their last point is that West Virginia failed to set a protective level for infants
exposed. They say that a C-8 level protective of bottle-fed infants would
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incorporate 3 more safety factors, giving an allowable level for C-8 in water of
1.5 ppb.
Response: It is true that West Virginia did not set a level specifically protective of
children or infants. However, in EPA's "Review of the Reference Dose and
Reference Concentration Processes" (the same document cited above), the panel
stated that in order to be protective of children, they recommended that
developmental toxicity data be used, whenever possible, to set the RfD. In the
absence of such data, they recommended that the extra uncertainty factor for
database deficiencies should be applied, which they felt would be protective of
children. Since the C-8 RfD, as calculated by West Virginia, was based on a
developmental toxicity study which should be protective for children, I do not
recommend calculating a separate number for children. As stated by the EWG, it is
true that bottle-fed infants receive the highest dose of all drinking water
contaminants, pound -for -pound compared to any other segment of the population.
However, EPA generally only sets health based numbers for infants in particular
situations where this sensitive subpopulation is known to be significantly affected.
New JerseAccording to the September 8 letter from DuPont, New Jersey has
adopted an "Interim Guidance Criteria' of 5 ppb for C-8. This value is not based on a
risk assessment but comes from guidance for the New Jersey Ground Water Quality
Standards which state that in situations where no specific criterion exists for a
synthetic organic chemical, the State of New Jersey should establish an interim
criterion of 5 ppb for compounds identified as "having evidence of carcinogenicity".
Since C-8 has been shown to be carcinogenic in rats, New Jersey has set the interim
criterion at 5 ppb. DuPont states in their letter that they do not believe that these
findings are relevant to humans; however New Jersey has used the potential
carcinogenicity of the compound as the basis for setting their number.
Recommendation for C-8 Number: I believe that the C-8 RfD calculated by the State
of West Virginia of 0.004 mg/kg-day is a good number based on the state of -the -art
in risk assessment. It was calculated by a panel of scientists using EPA's latest
guidance. In addition, another RfD (0.007 mg/kg-day) calculated by the West
Virginia panel based on a different study, as well as Minnesota's RfD (0.001 mg/kg-
day), are both in the same general range, further adding to my level of confidence in
this number.
However, I do not have the same level of confidence in West Virginia's screening
level for water of 150 ppb. As I said previously, I cannot find the guidance that it was
based on on EPA's website. One option (and the one that I favor) is to recalculate a
screening level, using the EPA method that was used by Minnesota to calculate their
Health -Based Value, and is also used by the EPA to calculate their Health Advisories
and other water health levels. The following is the formula and calculation:
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(RfD mg/kg-day) (relative source contribution) (1000 ua/mg)
Intake Rate (2 liters per day)/70 kg)
(0.004 mg/kg-day) (0.2) (1000 µg/mg) = 27.6 µg/L or 28 ppb
0.029 L/kg/day
A second option is to use Minnesota's Health -Based Value of 7 ppb. I prefer this
number over West Virginia's because it is more conservative and it incorporates the
20% relative source contribution factor. In addition, ATSDR cites this value in their
February, 2005 health consultation for the 3M facility in Cottage Grove, Minnesota.
Although Minnesota's RfD was calculated based on an older study compared with
West Virginia's, the final RfD of the two states, 0.001 mg/kg-day for Minnesota, and
0.004 mg/kg-day for West Virginia, are very close to each other.
A third option is to use West Virginia's screening level of 150 ppb. This is my 3ra
choice because of the reasons outlined above. However, this number does have one
advantage over the others: it was calculated by a panel of experts and went through
review and comment. Thus, it does have a degree of support behind it that would not
be there using the number I calculated (even though the number I calculated does use
West Virginia's RfD) or Minnesota's value.
A fourth and final option is to use New Jersey's 5 ppb interim criteria. This is my last
choice because the number was not based on science; it is a default value that New
Jersey uses in the absence of chemical -specific standards. However, this is the most
conservative value and could be supported on this basis.
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