Perfluorinated Sulfonamides in
Indoor and Outdoor Air and Indoor
Dust: Occurrence, Partitioning, and
M A H I B A S H O E I B , *, †T O M H A R N E R ,†
B R Y O N Y H . W I L F O R D ,† , ‡
K E V I N C . J O N E S ,‡A N D J I P I N G Z H U§
Meteorological Service of Canada, Air Quality Research
Branch, 4905 Dufferin Street, Toronto, Ontario, Canada,
M3H 5T4 Environmental Science Department, Institute of
Environmental and Natural Sciences, Lancaster University,
Lancaster, LA1 4YQ, UK, and Chemistry Research Division,
Health Canada, Ottawa, Ontario, Canada, K1L 0L2
Perfluorinated alkyl sulfonamides (PFASs) which are used
in a variety of consumer products for surface protection
air, house dust, and outdoor air in the city of Ottawa,
Canada. This study revealed new information regarding
the occurrence and indoor air source strength of several
PFASs including N-methylperfluorooctane sulfonamido-
ethanol (MeFOSE), N-ethylperfluorooctane sulfonamidoet-
hanol (EtFOSE), N-ethylperfluorooctane sulfonamide
(EtFOSA), and N-methylperfluorooctane sulfonamidethylacry-
late (MeFOSEA). Passive air samplers consisting of
polyurethane foam disks were calibrated and used to
conduct the indoor and outdoor survey. Indoor air
concentrations for MeFOSE and EtFOSE (1490 and 740 pg
m-3, respectively) were about 10-20 times greater than
source to the outside environment. EtFOSA and MeFOSEA
concentrations were lower in indoor air (40 and 29 pg
For indoor dust, highest concentrations were recorded
of 110 and 120 ng g-1, while concentrations for EtFOSA
and MeFOSEA were below detection and 7.9 ng g-1
respectively. MeFOSE and EtFOSE concentrations in house
dust followed levels in indoor air. However, resolution of
the coupled air and dust data (for the same homes) was
not successful using existing KOA-based models for surface-
air exchange. The partitioning to house dust was greatly
underpredicted. The difficulties with existing models may
be due to the high activity coefficient of PFASs in octanol
and/or a situation where the dust is greatly oversaturated
with respect to the air due to components of the dust being
contaminated with PFASs. A human exposure assessment
based on median air and dust concentrations revealed
that human exposure through inhalation (100% absorption
assumed) and dust ingestion were ∼40 and ∼20 ng
d-1, respectively. However, for children the dust ingestion
pathway was dominant and accounted for ∼44 ng d-1.
Perfluorooctane sulfonate (PFOS) has emerged as a priority
environmental pollutant due to its widespread detection in
biological samples from remote regions including the Arctic
and the Mid-North Pacific Ocean and its persistent and
compounds have also been detected in human blood from
several areas around the world (4-7). The mechanism by
is not understood. Because it has a low volatility and high
in remote regions is the result of atmospheric transport of
more volatile and neutral airborne contaminant precursors
related chemicals such as PFASs are used in a variety of
consumer products for water and oil resistance including
surface treatments for fabric, upholstery, carpet, paper, and
leather, in fire-fighting foams, and as insecticides (10).
Research on perfluorinated chemicals has increased dra-
matically in the past three years in an effort to understand
PFASs were first detected in air at urban and rural sites
in Canada with concentrations ranging from 13 to 393 pg
with highest concentrations observed near a carpet manu-
facturing facility in Griffin, Georgia (60-1500 pg m-3) (12).
Indoor air was shown to be a source of PFASs to the outside
(13). Indoor air concentrations were about 2 orders of
magnitude higher than outdoor levels. Furthermore, PFASs
partition coefficient) and supercooled liquid vapor pressure
(pL0) indicated that they should be entirely in the gas phase.
To better assess the long-range transport and fate
pathways of PFASs, more information is needed regarding
media, e.g., soil, vegetation, aerosols. Partitioning to dust
particles is particularly important for evaluating exposure
and intake of PFASs in indoor environments. People spend,
on average, more than 90% of their time indoors and this
exposure may serve as an important uptake pathway (14).
For children, exposure to contaminated house dust may
represent a particular concern since children spend a lot of
time on floors and carpets where dust accumulates; they
effect of PFOS and other fluorinated compounds is not fully
understood and still investigated, some research points to
the role of PFOS as an inhibitor of gap-junction intercellular
communication (16) and as a tumor promoter (17).
In this study polyurethane foam (PUF) disk passive air
samplers were used to conduct a survey of PFASs in indoor
air concentrations of persistent organic pollutants (POPs)
has already been demonstrated (18-20). The samples
collected in this study were previously analyzed to yield
indoor air concentrations of brominated flame retardants
(21). In addition to air samples, house dusts from the
* Correspondingauthorphone: +14167395961;fax: +1416739
5708; e-mail: Mahiba.Shoeib@ec.gc.ca.
†Meteorological Service of Canada.
Environ. Sci. Technol. 2005, 39, 6599-6606
10.1021/es048340y CCC: $30.25
Published on Web 08/02/2005
2005 American Chemical Society VOL. 39, NO. 17, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY96599
also analyzed. These combined results for PFAS concen-
trations in air and dust are used to evaluate (i) the role of
indoor environments as sources of PFASs to the outside,
(ii) partitioning of PFAS between air and dust, and (iii) hu-
man exposure to PFASs through inhalation and ingestion of
Sample Collection. Indoor air and dust were collected from
59 of 66 randomly selected homes in the city of Ottawa,
collected at seven sites across the city (21). Passive samplers
area 365 cm2, mass 4.40 g, volume 207 cm3, PacWill
Environmental, Stoney Creek, ON) that were individually
suspended in special chambers to prevent the deposition of
for approximately 21 days indoors and for approximately 70
elsewhere (21). Throughout the sampling period, clean PUF
disk travel blanks (n ) 7) were transported and stored with
real samples and then treated as samples during analysis.
Method detection limit (MDL) values for analytes were
by deploying duplicate samplers at seven homes and three
Passive samplers were calibrated against low-volume air
collected at a rate of approximately 2 L min-1using a BGI-
400-4 personal air sampling pump (BGI Incorporated,
Whatham, MA). Breakthrough was evaluated by fitting two
PUF plugs (22 mm outer diameter; 76 mm length for the
head (ORBO-1000, inside diamater (i.d.) 22 mm, from
Supelco, USA). The sampler inlet was oriented horizontally,
samplers. Both active and passive samplers were deployed
simultaneously for 17-20 days in indoor locations, mainly
offices and laboratories.
that used floor model vacuum cleaners, the bags were
sample bag (Fisher Scientific Ltd., Nepean, Ontario). For
central vacuum cleaners, dust stored in the reservoir
a glove-covered hand. Upon arrival in the laboratory (few
hours later), the bag was then cut open with clean scis-
sors and the content of the bag was transferred to a vibra-
tory siever (AS200 digit Analytical Sieve Shaker, Retsch
GmbH&Co.KG, 42781 Haan, Rheinische Str.36, Germany).
This consisted of a No. 16 sieve (U.S.A. Standard Testing
Sieve, A.S.T.M.E-11 Specification, opening 1.18 mm) above
a No. 100 sieve (U.S.A. Standard Testing Sieve, A.S.T.M.E-11
After sealing the top, the vibratory siever was run for 10 min
at an amplitude of 80. The dust was allowed to settle for 15
s, and the collection pan was removed and replaced with a
new one. The siever was run for an additional 5 min. Any
tweezers and/or a brush. Dust from the collection pans was
transferred to a 190 mm i.d.× 100 mm tall crystallizing dish.
When the entire sample was sieved, the dust from the
crystallizing dish was sieved one more time for 3 min. Three
grams of the resulting fine dust (<150 µm) was then
transferred to a 20-mL clear wide-mouth bottle with an
mL preweighed jars (VWR International Ltd, Montreal,
Quebec), using a stainless steel spatula. The dust samples
were stored at -20 °C until analysis. Sodium sulfate was
placed in the same types of bottles and stored together with
processed dust samples to serve as a combined storage and
analytical method blank.
Extractions. PUF samples were Soxhlet extracted for 21
Samples containing visible particles were filtered through a
glass pipette packed with glass wool using petroleum ether
eluate. Recoveries of N-methylperfluorooctane sulfonami-
doethanol (MeFOSE), N-ethylperfluorooctane sulfonami-
doethanol (EtFOSE), N-ethylperfluorooctane sulfonamide
(EtFOSA), and N-methylperfluorooctane sulfonamidethyl-
acrylate (MeFOSEA) (∼120 ng), were determined by spiking
in two stages, first using petroleum ether for 21 h, followed
by acetone for 21 h. Dust extractions were performed by
with dichloromethane (DCM) for 24 h. To test recoveries,
h each) using DCM. Mirex (0.1 ng) was added as an internal
response. No cleanup of extracts was performed for PUF or
FIGURE 1. Schematic diagram of indoor (a) and outdoor (b) passive air samplers.
66009ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 17, 2005
Chemicals. The target compounds and their molecular
formulas are given in Table 1. All PFASs were obtained from
the 3M Company, with purities >90%.
Analysis. PFASs were analyzed by gas chromatography
electron impact mass spectrometry (GC-EIMS) using a
in selective ion monitoring (SIM) mode. Confirmation was
performed on selected samples using negative chemical
ionization (NCI) in SIM mode, where methane was used as
on a 60-m DB5 column with 0.25 mm i.d. and 0.25 µm film
thickness with helium as the carrier gas. The GC oven
temperature was 60 °C, 0.5 min, 3 °C min-1to 160 °C, then
opened after 0.5 min and the injector at 250 °C. The ion
source and quadrupole were kept at 230 and 150 °C for EI
and 150 and 106 °C, respectively, for NCI analysis. Analysis
details are given in Table 1. Standards were included every
12 samples to monitor changes in instrument sensitivity.
Subsets of all dust samples were sent for total organic and
inorganic carbon analysis (Laboratory Services, University
of Guelph, ON).
Results and Discussion
target/qualifier ion ratios (Table 1) were within 20% of the
values in the standards. The MDL equivalent air concentra-
were 7 and 5 pg m-3for MeFOSE and EtFOSE, respectively,
assuming an air volume of 70 m3(Table 2). EtFOSA and
MeFOSEA were not detected in the travel blanks. In these
cases the MDL value was considered to be equal to two-
thirds of the instrument detection limit (IDL). The IDL was
that could be integrated and corresponds to a chromato-
graphic peak with a signal/noise ratio of 3/1. Results are
blank extracts (n ) 3). Since all blank samples were below
detection, MDLs of the targets in dust were assigned based
on IDL as discussed above. No blank correction was applied
to reported air and dust concentrations.
PUF recoveries showed that more than 98% of target
compounds were extracted by the first petroleum ether
This was consistent with previous work (13). Overall,
recoveries were greater than 87% with the exception of
MeFOSEA for which recoveries were lower at 64% (Table 2).
For dust samples, all target analytes were contained entirely
in the first extract, indicating that a single 24-h extract with
DCM was sufficient. Results for samples were not recovery
corrected. It should be noted that, at the time of the study,
not available for performing surrogate recoveries.
Good agreement was obtained for all 10 sets of duplicate
the exception of one set (17% for MeFOSE) (Table 3). For
sites where duplicate samplers were deployed, the average
of the two values is reported.
Results of the breakthrough tests for the low-volume
sampler showed that although some breakthrough of target
analytes to the second PUF did occur it was less than 25%.
Therefore, the sum of the front and back PUFs was used to
evaluate the PUF disk sampling rate.
Calibration Study: Passive Sampler Uptake Rate. The
PUF disk air sampling rate was determined by calibrating
was conducted at eight indoor locations and is described in
detail by Wilford et al. (21). The resulting sampling rate for
the PFASs was approximately 2.5 m3d-1, in good agreement
with the sampling rate previously determined for polybro-
minated diphenyl ethers (21). On the basis of this rate, an
air volume of approximately 52.5 m3was sampled for the
21-day indoor deployment and approximately 175 m3for
the 70-day outdoor period.
is due to the PUF disk samplers collecting mainly gas-phase
both gas- and particle-phase contributions. This results in
an underestimate for the passive air sampling rate of 2.5 m3
d-1and explains why this value is lower than the usual value
of 3.5-4 m3d-1derived in other studies using the same PUF
disks (18-20). Consequently, passive sampler-derived gas-
phase concentrations could be biased high up to ∼40% as
results of lower sampling rate indicated above (note: since
concentrations are calculated as (amount of analyte on PUF
disk/(sampling rate × number of days the PUF disk was
exposed)). However, the extent of the bias will depend on
and which were not part of the sampling strategy for this
sampler-derived air concentrations for the target com-
pounds in indoor and outdoor air are presented in Figure 2
and Table 4.
MeFOSE. Highest air concentrations were observed for
MeFOSE which was log normally distributed in indoor air
with a geometric mean value of 1490 pg m-3(Figure 2a),
compared to the arithmetic mean value of 1970 pg m-3; this
was approximately 18 times greater than the outdoor value
of 82 pg m-3. The only other indoor air concentrations for
MeFOSE were reported by Shoeib et al. (13) for a survey of
homes and laboratories. In that study MeFOSE also domi-
nated and ranged from 11 to 8000 pg m-3. Outdoor air
in Toronto (urban) and Long Point (a rural location on the
north shore of Lake Erie) concentrations ranged from 86 to
123 and 34 to 36 pg m-3, respectively (8). Outdoor air
concentrations for residential areas in Toronto were also
TABLE 1. Structural and Analytical Information for the PFASs Investigated in This Study
compounds acronymmolecular formula EI ionsNCI ions
N-methyl perfluorooctane sulfonamidoethanol
N-ethyl perfluorooctane sulfonamidoethanol
N-ethyl perfluorooctane sulfonamide
N-methyl perfluorooctane sulfonamidethylacrylate
C8F17SO2N(CH3) CH2CH2OCOCH dCH2
TABLE 2. Analytical Details for PFASs by EI-MS Analysis:
IDLs, MDLs, and Method Recoveries
compoundsIDL (pg) MDLa(pg m-3)
(SD) PUF (n ) 4)
aMDL calculated as average blank (n ) 7) +3 standard deviations
air volume of 70 m3.
VOL. 39, NO. 17, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY96601
reported with values ranging from 16 to 32 pg m-3(13).
MeFOSE concentrations reported in several locations in
North America ranged from 20 pg m-3to almost 400 pg m-3
in Griffin, Georgia; this elevated value was attributed to a
high density of potential point sources (carpet treatment
facilities) in the region (12).
EtFOSE. Results for EtFOSE are shown in Figure 2a
arranged according to the same sample order used to
concentrations are also log normally distributed, they are
they may arise from different sources. The geometric mean
indoor air concentrations for EtFOSE was 744 pg m-3, about
8.5 times greater than the outdoor value of 87 pg m-3.
Such high indoor air concentrations of EtFOSE were not
expected. To our knowledge, EtFOSE is mainly used for
treating food wrapping. It is possible however, that EtFOSE
may also occur as a byproduct in the manufacture of other
or that other important uses exist which have not yet been
considered. Outdoor air concentrations ranged from 51 to
393 pg m-3in Toronto to 68 to 85 pg m-3at Long Point (8).
air concentrations in a survey across North America ranged
from below detection to a high of ∼200 pg m-3in Reno,
EtFOSA and MeFOSEA. Indoor air concentrations for
EtFOSA and MeFOSEA (Figure 2b) were about an order of
magnitude lower than for MeFOSE and EtFOSE (Figure 2a).
Results in Figure 2b are arranged according to the same
sample sequence used in Figure 2a. EtFOSA was detected in
more than 90% of the indoor samples and had a geometric
mean value of 40 pg m-3. Outdoor samples were below
detection. Outdoor air concentrations for EtFOSA ranged
from below detection to ∼60 pg m-3in Reno Nevada (12),
while 14 pg m-3was reported in Toronto (8).
In this study, MeFOSEA was above the detection limit in
only 15% of samples with a geometric mean of 29 pg m-3.
MeFOSEA was not detected in outdoor samples. The only
TABLE 3. Comparison of PFASs Air Concentrations at Sites Where Duplicate PUF Disk Samplers Were Deployed
aOutdoor PUF disk samples.bBDL ) below method detection limit (MDL, see Table 2).
FIGURE 2. Passive sampler-derived air concentrations (pg m-3) in outdoor and indoor air for (a) MeFOSE and EtFOSE and (b) EtFOSA and
MeFOSEA. Sample order is the same in a and b and follows increasing concentrations of MeFOSE.
66029ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 17, 2005
previous measurement of MeFOSEA in air was in the study
by Shoeib et al. (13) where levels in indoor air ranged from
below detection to ∼5 pg m-3, with one house exhibiting a
high value of 283 pg m-3.
PFAS Concentrations in Indoor Dust. Results for dust
these are the first measurements of these compounds in
indoor dust although PFOS and perfluorooctanoic acid
(PFOA) were detected in house dust in Japan with concen-
trations ranging from 11 to 2500 and 69 to 3700 ng g-1,
Consistent with the indoor air measurements, highest
were also log normally distributed as shown for MeFOSE in
Figure 3 where results are again arranged according to
samples with increasing dust concentrations of MeFOSE.
No correlation exists between MeFOSE and EtFOSE dust
dust. MeFOSEA was detected in ∼30% of dust samples with
a geometric mean value of ∼ 8 ng g-1.
Dust-Air Partitioning of PFASs. It is useful to evaluate
regarding the environmental fate of these compounds and
to evaluate the potential for human expsosure via dust
ingestion and inhalation. One might speculate that, if these
chemicals (specifically MeFOSE and EtFOSE) arise from a
act as equilibration chambers. In this scenario, chemicals
strive to distribute themselves equally (in fugacity terms)
between media in an approach to equilibrium. It is likely
that home ventilation (i.e., replacement of indoor air with
outdoor air) plays a key role in preventing indoor air
concentrations from becoming excessively high. Home
ventilation is also a pathway for delivery of contaminated
indoor air to the outside environment.
As this study was conducted during the winter period
in Ottawa, we can assume that windows and doors were
closed and that ventilation rates in these homes were
relatively low and controlled mainly by the furnace systems
and human traffic. These were ideal conditions for the dust-
air equilibration scenario. Figure 4 compares paired dust
and air concentrations for the same homes for MeFOSE and
EtFOSE. Although there is considerable scatter in the data,
there is generally a good agreement with higher dust
(p < 0.001). Dust concentrations in Figure 4 were converted
to a mass/volume basis (pg contaminant in cubic meter of
dust) using a value of 1 kg L-1for the density of dust. This
was based on several preliminary tests that involved adding
dust to water, shaking, and observing that the bulk of the
dust remained suspended in water.
Previous work has shown that the KOA-based model of
particle-gas partitioning greatly underpredicts particulate
(13). In that approach, the KOA-based model results were
concentration of chemical on particles (ng µg-1particles)
and CAis the concentration in air (gas phase) (ng m-3).
In this study, an analoguos model, the Karickhoff model,
is used to predict concentrations on dust from air concen-
trations of PFASs. If air-dust equilibrium is assumed, the
concentration on dust can be predicted from air concentra-
where KDAis the dust air partition coefficient, FDthe density
of dust, and fOC is the organic carbon content of dust.
Supplement 1 provides a more detailed explanation of the
model and background. Log KOA values for MeFOSE and
EtFOSE were 7.70 and 7.78, respectively (13). Values of fOC
were determined for each dust sample and on average were
0.23 ( 0.06, and dust density was 1 kg L-1as discussed
The concentration on dust that is predicted using eq 1 is
compared to the measured dust concentrations in Figure 5.
The results indicate that the Karickhoff model greatly
underpredicts (by about 1 order of magnitude) the extent to
which MeFOSE and EtFOSE are associated with particles.
to compare particle-phase and gas-phase components of
PFASs from high volume indoor air samples. These findings
suggest that either the KOA-based model needs to be
parameter for dust/particle to air partitioning of PFASs. To
partitioning data for several PFASs that span a range of KOA
against KOAon a log-log basis and observing a slope close
The failure of the existing KOA-based partitioning models
is likely due to large interaction effects of the surfactants in
The activity coefficient in octanol estimated from the values
of pL0and KOAreported by Shoeib et al. (13) result in a value
of approximately 150 for MeFOSE and 30 for EtFOSE. This
is about 1 order of magnitude higher than the average value
for more than 200 organic chemicals (23) and may explain
the uncharacteristic partitioning behavior (in terms of KOA)
of the PFASs.
is that the dust and air are in disequilibrium; the dust may
contain components that are highly contaminated with
PFASs. The PFASs may be either too tightly bound to these
Statistical Analysis. An attempt was made to relate air
and dust concentrations to house characteristics obtained
TABLE 4. Concentrations of PFAS in Indoor and Outdoor Air
Samples and Indoor Dusta
Outdoor Air, pg m-3
Indoor Air, pg m-3
arithmetic mean (SD)
arithmetic mean (SD) 1970 (1610)
1100 (1420) 59 (91) 35 (27)
Indoor Dust, ng g-1
412 (1180) 2200 (9750) BDL
arithmetic mean (SD)
aNote: average organic carbon content of dust samples was 23.9%
( 6.0.bBDL ) below method detection limit.
KDA) 0.411FDfOCKOA) CDUST/CAIR
VOL. 39, NO. 17, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY96603
correlated (Figure 4), it was sufficient to carry out the
evaluation on just the air data. The results of the statistical
analysis showed some marginally significant trends; for
total MeFOSE + EtFOSE (p ) 0.037) in the seven homes
during the previous 6-month period. Also a marginally
significantly lower level of MeFOSE (p ) 0.024) and signifi-
cantly lower levels of MeFOSE + EtFOSE (p ) 0.0084) were
compared to single-house homes. No correlations were
observed between levels of PFASs and house age and/or
extent of carpeting. Unfortunately, questions dealing with
home ventilation rates were not adequately captured in the
questionnaire, and hence this factor was not further evalu-
Human Exposure. PFOS has been detected in human
this uptake occurs directly (i.e., as PFOS) as it was detected
in house dust (22) and/or by biotransformation of some
precursor to PFOS, such as the PFASs (9). It has also been
suggested that PFASs may be degraded to PFOS directly in
FIGURE 3. Concentration of MeFOSE and EtFOSE in house dust collected from 66 homes. Sample order follows increasing concentrations
FIGURE 4. Correlation of air and dust concentrations from the same homes for MeFOSE and EtFOSE. Note that dust concentrations are
expressed as pg m-3of dust assuming a dust density of 1 kg L-1.
66049ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 17, 2005
the atmosphere (8). The high level of PFAS in indoor air and
dust where people spend most of their time urges the need
pathways. Exposure to contaminated dust is particularly of
concern for children; not only do children spend a lot of
time on floors and carpets where dust accumulates but they
frequently put their hands and other objects into their
mouths, increasing their ingestion of dust. Overall, infants
and toddlers ingest about twice as much dust as adults per
On the basis of measured PFAS concentrations in air and
for PFASs, 100% absorption (worst case scenario) was
assumed. Light activity inhalation rates of 20, 19, and 13 L
min-1for male (m), female (f), and children up to 10 years
old, respectively, were used in these calculations (25).
different across gender. It was assumed that 16 h per day
were spent on light activity. The remaining time of the day
was spent resting or outdoors. Exposure while at rest or
(and not included) due to low inhalation rates during rest
and low outdoor air concentrations. The US Environemntal
Protection Agency (EPA) (15) estimates that children (1-6
years of age) ingest ∼200 mg dust day-1, while the figure for
adults is 100 mg day-1.
scenarios: (1) using the lowest 10th percentile air and dust
concentrations of MeFOSE and EtFOSE, (2) using median
levels, and (3) using 90th percentile levels. In most cases the
dominant pathway for adult exposure is via inhalation. For
instance, under scenario 2 (median air and dust concentra-
tions), inhalation and dust ingestion result in 60 ng day-1
taken up; almost two-thirds of this is due to inhalation.
range 44 ng day-1compared to 27 ng day-1via inhalation.
For people living in the 10% of homes with highest air and
dust levels (90th percentile), ingestion is the dominant
pathway, accounting for 412 ng day-1compared to ∼130 ng
uptake is estimated to be ∼825 ng day-1san order of
magnitude greater than the inhalation value of 82 ng day-1.
It should be emphasized that results in Table 5 represent
the worse case scenario (i.e., 100% absorption assumed and
indoor air concentrations taken in winter time when ventila-
tion is low). Levels of PFAS in indoor air are expected to vary
seasonally and decrease during the milder periods (e.g.,
summer) when windows are open and indoor air is diluted
by relatively cleaner outdoor air.
dust are an important human exposure route for PFASs,
comparisons with dietary exposure as these data become
available. (ii) Indoor air is an important source of PFASs to
the outside environment, again, especially for MeFOSE and
be possible to make fairly good estimates of environmental
emission rates based on the data presented here and
information on home ventilation. It is also necessary to
investigate if there are other point sources of PFASs (aside
from indoor air, e.g., industrial, manufacturing) that may be
important. (iii.) Last, this study confirms findings from
previous work (13) and suggests that KOA-based partitioning
This is an area for further study and has implications for our
Supporting Information Available
material is available free of charge via the Internet at http://
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TABLE 5. Estimated Human Exposure to PFASs via Inhalation
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Received for review October 25, 2004. Revised manuscript
received March 2, 2005. Accepted June 2, 2005.
66069ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 17, 2005