DEQ-CFW_00058101

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ABSTRACT
Perfluorooctane sulfonate (PFOS) exposure in the general
population is widespread but gradually declining, due to
the large-scale phase -out of PFOS manufacture beginning
in the early 2000s. Estimated PFOS intake from all sources
is relatively low, on the order of 0.01 µg/kg-day or less.
Exposure sources forthe general population include food,
drinking water, and house dust, with diet as the largest
source. Several agencies In the US and abroad have
established daily Intake guidelines. Recently, bath the
United States Environmental Protection Agency (US EPA,)
and the Agency forToxic Substances and Disease Registry
(ATSDR) proposed values of 0.03 µg/kg-day, and the UK
Tolerable Daily Intake (TDI) is 0.3 µg/kg-day. Rased on these
values, agencies have also set drinking water guidelines.
These guidelines use either 10 or 20% as default values
for the relative source contribution (RSC) from drinking
water. Applying these default RSC values, in addition to
relying on very conservative toxicological endpoints, likely
yields drinking water guidelines that are unnecessarily
conservative. We assessed the relative intake of PFOS from
water, food, and other sources to establish alternative RSCs
for PFOS. We reviewed data on estimated intake of PFOS
from food and other sources and reviewed the assumptions
used as the basis for the drinking water guidelines for
PFOS. Given the relatively small total intake of PFOS from
food (e.g., approximately 0.005 µg/kg-day or less), current
drinking water guidelines are likely to overestimate the
relative contribution from food and other sources and
thus underestimate the RSC. Using the UK drinking water
guideline as an example, we demonstrate that the use
of more scientifically supported RSC values would yield
health -protective drinking water guidelines that are more
than four -fold higher than the current guideline.
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OBJECTIVE
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1
Calculate an alternative UK health -based value for acceptable maximum PFOS concentrations in drinking water, based
on published average dietary PFOS intake values in Western populations.
BACKGROUND
PFOS is a man-made chemical with surfactant properties that was used in fire -fighting foams, hydraulic fluids, carpet
cleaners, furniture and clothing treatments, and other products until it was voluntarily phased out of use beginning
in 2002.
• Low levels of PFOS can be found in sail, groundwater and surface water, animals, and plants.
• Diet is the largest source of PFOS exposures contributing between 91 and 96% of total exposure in most
Western countries.
• Despite the relative Importance of diet compared to other sources, the absolute amount of PFOS exposure aria food is
generally low.
• Some agencies have developed health -protective toxicity criteria and accompanying drinking outer guidelines;
these values are derived using toxicology studies and data on exposure levels.
Calculations require estimating the RSC of water to total PFOS intake, default values are 10-20%.
• Current drinking water guideline in the UK is 1 µg/L, which the UK considers protective of adults and children.
* Conducted a literature search on PFOS exposure sources.
o Calculated an RSC using dietary data, as follows:
o Calculated alternative drinking water guidelines for infants
and adults in the UK, as follows
Notes: a116=Drinkin aMaier 6Wdeline; iDi=lolerableDa;lvintake(O.31fgilg-dav); BW =Body Weight;
1R=ingestionRatc; RSC = Relative SourceContdbution.
a
T6el Est�mAWF Intake'
Notes: (a) Other than drinking water. (b) Based on 9101 of 10 kg. (c) Based on BVIl of7O kg.
P
X.
® Air and dust concentrations are from Fromme etal. (2009); we used high -end values for outdoor air and dust and a
mean value for indoor air (only a mean was available for indoor air).
• Indoor/outdoor air inhalation rates and dust ingestion rates are as recommended by US EPA, (2011) for central tendency
rates for a 0- to 1-year-old infant, assuming 90% of day spent indoors (Fromme etai., 2009).
• Dietary intake is the upper end of the 95' percentile for infants from the European Food Safety Authority (EFSAa, 2012).
• Air and dust intake values are the high -end estimates from Fromme etal. (2009).
• Dietary intake is based on the upper end of the median estimate of the 9511' percentile, as estimated by EFSA (2012).
TMAe
Notes: (a) Valuenot based on data; implicit from assumption of 1O% ofTDl from water.
Diet + 0 t h e r
Water
Diet
Water
Dust
Air
CONCLUSION
o Current UK guidelines Implicitly overestimate exposure
to PFOS aria diet and other non -water sources.
e Calculations indicate that, in the UK, the RSC of water
to total PFOS exposure could be higher than current
default values.
e Alternate water RS s would yield PFOS drinking water
guidelines that are higher than current levels and remain
health -protective of all age groups.
e Accurately estimating population -specific PFOS exposure
from all sources is critical to setting safe, scientifically
supported PFOS drinking water guidelines.
DEQ-CFW 00058101