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Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina

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Long-chain per- and polyfluoroalkyl substances (PFASs) are being replaced by short-chain PFASs and fluorinated alternatives. For ten legacy PFASs and seven recently discovered perfluoroalkyl ether carboxylic acids (PFECAs), we report (1) occurrence in the Cape Fear River (CFR) watershed, (2) fate in water treatment processes, and (3) adsorbability on powdered activated carbon (PAC). In the headwater region of the CFR basin, PFECAs were not detected in raw water of a drinking water treatment plant (DWTP), but concentrations of legacy PFASs were high. The US Environmental Protection Agency’s lifetime health advisory level (70 ng/L) for perfluorooctane sulfonic acid and perfluorooctanoic acid (PFOA) was exceeded on 57 of 127 sampling days. In raw water of a DWTP downstream of a PFAS manufacturer, the mean concentration of perfluoro-2-propoxypropanoic acid (PFPrOPrA), a replacement for PFOA, was 631 ng/L (n=37). Six other PFECAs were detected with three exhibiting chromatographic peak areas up to 15 times that of PFPrOPrA. At this DWTP, PFECA removal by coagulation, ozonation, biofiltration, and disinfection was negligible. PFAS adsorbability on PAC increased with increasing chain length. Replacing one CF2 group with an ether oxygen decreased PFAS affinity for PAC, while replacing additional CF2 groups did not lead to further affinity changes.
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Legacy and Emerging Peruoroalkyl Substances Are Important
Drinking Water Contaminants in the Cape Fear River Watershed of
North Carolina
Mei Sun,*
,,
Elisa Arevalo,
Mark Strynar,
§
Andrew Lindstrom,
§
Michael Richardson,
Ben Kearns,
Adam Pickett,
Chris Smith,
#
and Detlef R. U. Knappe
Department of Civil and Environmental Engineering, University of North Carolina at Charlotte, Charlotte, North Carolina 28223,
United States
Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina
27695, United States
§
National Exposure Research Laboratory, U.S. Environmental Protection Agency Research, Triangle Park, North Carolina 27711,
United States
Cape Fear Public Utility Authority, Wilmington, North Carolina 28403, United States
Town of Pittsboro, Pittsboro, North Carolina 27312, United States
#
Fayetteville Public Works Commission, Fayetteville, North Carolina 28301, United States
*
SSupporting Information
ABSTRACT: Long-chain per- and polyuoroalkyl substances
(PFASs) are being replaced by short-chain PFASs and
uorinated alternatives. For ten legacy PFASs and seven
recently discovered peruoroalkyl ether carboxylic acids
(PFECAs), we report (1) their occurrence in the Cape Fear
River (CFR) watershed, (2) their fate in water treatment
processes, and (3) their adsorbability on powdered activated
carbon (PAC). In the headwater region of the CFR basin,
PFECAs were not detected in raw water of a drinking water
treatment plant (DWTP), but concentrations of legacy PFASs
were high. The U.S. Environmental Protection Agencys
lifetime health advisory level (70 ng/L) for peruorooctane-
sulfonic acid and peruorooctanoic acid (PFOA) was exceeded on 57 of 127 sampling days. In raw water of a DWTP
downstream of a PFAS manufacturer, the mean concentration of peruoro-2-propoxypropanoic acid (PFPrOPrA), a replacement
for PFOA, was 631 ng/L (n= 37). Six other PFECAs were detected, with three exhibiting chromatographic peak areas up to 15
times that of PFPrOPrA. At this DWTP, PFECA removal by coagulation, ozonation, bioltration, and disinfection was negligible.
The adsorbability of PFASs on PAC increased with increasing chain length. Replacing one CF2group with an ether oxygen
decreased the anity of PFASs for PAC, while replacing additional CF2groups did not lead to further anity changes.
INTRODUCTION
Per- and polyuoroalkyl substances (PFASs) are extensively
used in the production of plastics, water/stain repellents,
reghting foams, and food-contact paper coatings. The
widespread occurrence of PFASs in drinking water sources is
closely related to the presence of sources such as industrial
sites, military re training areas, civilian airports, and waste-
water treatment plants.
1
Until 2000, long-chain peruoroalkyl
sulfonic acids [CnF2n+1SO3H; n6 (PFSAs)] and peruoro-
alkyl carboxylic acids [CnF2n+1COOH; n7 (PFCAs)] were
predominantly used.
2
Accumulating evidence about the
ecological persistence and human health eects associated
with exposure to long-chain PFASs
3,4
has led to an increased
level of regulatory attention. Recently, the U.S. Environmental
Protection Agency (USEPA) established a lifetime health
advisory level (HAL) of 70 ng/L for the sum of
peruorooctanoic acid (PFOA) and peruorooctanesulfonic
acid (PFOS) concentrations in drinking water.
5,6
Over the past
decade, production of long-chain PFASs has declined in Europe
and North America, and manufacturers are moving toward
short-chain PFASs and uorinated alternatives.
710
Some
uorinated alternatives were recently identied,
8,11
but others
remain unknown
1214
because they are either proprietary or
manufacturing byproducts.
Received: October 13, 2016
Revised: November 8, 2016
Accepted: November 10, 2016
Published: November 10, 2016
Letter
pubs.acs.org/journal/estlcu
© XXXX American Chemical Society ADOI: 10.1021/acs.estlett.6b00398
Environ. Sci. Technol. Lett. XXXX, XXX, XXXXXX
One group of uorinated alternatives, peruoroalkyl ether
carboxylic acids (PFECAs), was recently discovered in the Cape
Fear River (CFR) downstream of a PFAS manufacturing
facility.
11
Identied PFECAs included peruoro-2-methoxy-
acetic acid (PFMOAA), peruoro-3-methoxypropanoic acid
(PFMOPrA), peruoro-4-methoxybutanoic acid (PFMOBA),
peruoro-2-propoxypropanoic acid (PFPrOPrA), peruoro-
(3,5-dioxahexanoic) acid (PFO2HxA), peruoro(3,5,7-trioxa-
octanoic) acid (PFO3OA), and peruoro(3,5,7,9-tetraoxadeca-
noic) acid (PFO4DA) (Table S1 and Figure S1). The
ammonium salt of PFPrOPrA is a known PFOA alternative
15
that has been produced since 2010 with the trade name
GenX. To the best of our knowledge, the only other
published PFECA occurrence data are for PFPrOPrA in Europe
and China,
15
and no published data about the fate of PFECAs
during water treatment are available. Except for a few studies
(most by the manufacturer),
1620
little is known about the
toxicity, pharmacokinetic behavior, or environmental fate and
transport of PFECAs.
The strong CF bond makes PFASs refractory to abiotic and
biotic degradation,
21
and most water treatment processes are
ineective for legacy PFAS removal.
2227
Processes capable of
removing PFCAs and PFSAs include nanoltration,
28
reverse
osmosis,
25
ion exchange,
28,29
and activated carbon adsorp-
tion,
28,29
with activated carbon adsorption being the most
widely employed treatment option.
The objectives of this research were (1) to identify and
quantify the presence of legacy PFASs and emerging PFECAs
in drinking water sources, (2) to assess PFAS removal by
conventional and advanced processes in a full-scale drinking
water treatment plant (DWTP), and (3) to evaluate the
adsorbability of PFASs on powdered activated carbon (PAC).
MATERIALS AND METHODS
Water Samples. Source water of three DWTPs treating
surface water in the CFR watershed was sampled between June
14 and December 2, 2013 (Figure S2). Samples were collected
from the raw water tap at each DWTP daily as either 8 h
composites (DWTP A, 127 samples) or 24 h composites
(DWTP B, 73 samples; DWTP C, 34 samples). Samples were
collected in 250 mL HDPE bottles and picked up (DWTPs A
and B) or shipped overnight (DWTP C) on a weekly basis. All
samples were stored at room temperature until they were
analyzed (within 1 week of receipt). PFAS losses during storage
were negligible on the basis of results of a 70 day holding study
at room temperature. On August 18, 2014, grab samples were
collected at DWTP C after each unit process in the treatment
train [raw water ozonation, coagulation/occulation/sedimen-
tation, settled water ozonation, biological activated carbon
(BAC) ltration, and disinfection by medium-pressure UV
lamps and free chlorine]. Operational conditions of DWTP C
on the sampling day are listed in Table S2. Samples were
collected in 1 L HDPE bottles and stored at room temperature
until they were analyzed. On the same day, grab samples of
CFR water were collected in six 20 L HDPE carboys at William
O. Huske Lock and Dam downstream of a PFAS manufacturing
site and stored at 4 °C until use in PAC adsorption experiments
(background water matrix characteristics listed in Table S3).
Adsorption Experiments. Adsorption of PFASs by PAC
was studied in batch reactors (amber glass bottles, 0.45 L of
CFR water). PFECA adsorption was studied at ambient
concentrations (1000 ng/L PFPrOPrA, chromatographic
peak areas of other PFECAs being approximately 10800%
of the PFPrOPrA area). Legacy PFASs were present at low
concentrations (<40 ng/L) and spiked into CFR water at
1000 ng/L each. Data from spiked and nonspiked experi-
ments showed that the added legacy PFASs and methanol (1
ppmv) from the primary stock solution did not aect native
PFECA removal. A thermally activated, wood-based PAC
(PicaHydro MP23, PICA USA, Columbus, OH; mean diameter
of 12 μm, BET surface area of 1460 m2/g)
30
proven to be
eective for PFAS removal in a prior study
29
was used at doses
of 30, 60, and 100 mg/L. These doses represent the upper
feasible end for drinking water treatment. Samples were taken
prior to and periodically after PAC addition for PFAS analysis.
PFAS losses in PAC-free blanks were negligible.
PFAS Analysis. Information about analytical standards and
liquid chromatographytandem mass spectrometry (LCMS/
MS) methods for PFAS quantication is provided in the
Supporting Information.
RESULTS AND DISCUSSION
Occurrence of PFASs in Drinking Water Sources. Mean
PFAS concentrations in source water of three DWTPs treating
surface water from the CFR watershed are shown in Figure 1.
In communities A and B, only legacy PFASs were detected
(mean PFAS of 355 ng/L in community A and 62 ng/L in
community B). Detailed concentration data are shown in Table
S6 and Figure S3. In community A, PFCAs with four to eight
total carbons, peruorohexanesulfonic acid (PFHxS), and
PFOS were detected at mean concentrations above the
quantitation limits (QLs). During the 127 day sampling
campaign, the sum concentration of PFOA and PFOS exceeded
the USEPA HAL of 70 ng/L on 57 days. The mean sum
concentration of PFOA and PFOS over the entire study period
was 90 ng/L, with approximately equal contributions from
PFOS (44 ng/L) and PFOA (46 ng/L). Maximum PFOS and
PFOA concentrations were 346 and 137 ng/L, respectively.
Similar PFOS and PFOA concentrations were observed in the
same area in 2006,
31
suggesting that PFAS source(s) upstream
of community A have continued negative impacts on drinking
water quality. Also, our data show that legacy PFASs remain as
surface water contaminants of concern even though their
production was recently phased out in the United States. It is
important to note, however, that among the PFCAs that were
measured in both 2006 and 2013 (PFHxA to PFDA), the
PFCA speciation shifted from long-chain (8085%
CnF2n+1COOH; n=79) in 2006 to short-chain (76%
CnF2n+1COOH; n=56) in 2013. In contrast, the PFSA
speciation was dominated by PFOS in both 2006 and 2013.
Figure 1. Occurrence of PFASs at drinking water intakes in the CFR
watershed. Concentrations represent averages of samples collected
between June and December 2013. Individual samples with
concentrations below the quantitation limits (QLs) were considered
as 0 when calculating averages, and average concentrations below the
QLs were not plotted.
Environmental Science & Technology Letters Letter
DOI: 10.1021/acs.estlett.6b00398
Environ. Sci. Technol. Lett. XXXX, XXX, XXXXXX
B
Relating total PFAS concentration to average daily streamow
(Figure S4) illustrated a general trend of low PFAS
concentrations at high ow, and high concentrations at low
ow, consistent with the hypothesis of one or more upstream
point sources.
In community B, peruorobutanoic acid (PFBA) and
peruoropentanoic acid (PFPeA) were most frequently
detected with mean concentrations of 12 and 19 ng/L,
respectively. Mean PFOA and PFOS concentrations were
below the QLs, and the maximum sum concentration of PFOA
and PFOS was 59 ng/L. Lower PFAS concentrations in
community B relative to community A can be explained by the
absence of substantive PFAS sources between the two
communities, dilution by tributaries, and the buering eect
of Jordan Lake, a large reservoir located between communities
A and B.
In community C (downstream of a PFAS manufacturing
site), only mean concentrations of PFBA and PFPeA were
above the QLs. The relatively low concentrations of legacy
PFASs in the nished drinking water of community C are
consistent with results from the USEPAs third unregulated
contaminant monitoring rule for this DWTP.
32
However, high
concentrations of PFPrOPrA were detected (up to 4500 ng/
L). The average PFPrOPrA concentration (631 ng/L) was
approximately 8 times the average summed PFCA and PFSA
concentrations (79 ng/L). Other PFECAs had not yet been
identied at the time of analysis. Similar to communities A and
B, the highest PFAS concentrations for community C were also
observed at low ow (Figure S4). Stream ow data were used
in conjunction with PFPrOPrA concentration data to
determine PFPrOPrA mass uxes at the intake of DWTP C.
Daily PFPrOPrA mass uxes ranged from 0.6 to 24 kg/day with
a mean of 5.9 kg/day.
Fate of PFASs in Conventional and Advanced Water
Treatment Processes. To investigate whether PFASs can be
removed from impacted source water, samples from DWTP C
were collected at the intake and after each treatment step.
Results in Figure 2 suggest conventional and advanced
treatment processes (coagulation/occulation/sedimentation,
raw and settled water ozonation, BAC ltration, and
disinfection by medium-pressure UV lamps and free chlorine)
did not remove legacy PFASs, consistent with previous
studies.
2226
The data further illustrate that no measurable
PFECA removal occurred in this DWTP. Concentrations of
some PFCAs, PFSAs, PFMOPrA, PFPrOPrA, and PFMOAA
may have increased after ozonation, possibly because of the
oxidation of precursor compounds.
25
Disinfection with
medium-pressure UV lamps and free chlorine (located between
the BAC euent and the nished water) may have decreased
concentrations of PFMOAA, PFMOPrA, PFMOBA, and
PFPrOPrA, but only to a limited extent. Small concentration
changes between treatment processes may also be related to
temporal changes in source water PFAS concentrations that
occurred in the time frame corresponding to the hydraulic
residence time of the DWTP.
Results in Figure 2 further illustrate that the PFAS signature
of the August 2014 samples was similar to the mean PFAS
signature observed during the 2013 sampling campaigns shown
in Figure 1; i.e., PFPrOPrA concentrations (400500 ng/L)
greatly exceeded legacy PFAS concentrations. Moreover, three
PFECAs (PFMOAA, PFO2HxA, and PFO3OA) exhibited peak
areas 2113 times greater than that of PFPrOPrA (Figure 2b).
The existence of high levels of emerging PFASs suggests a need
for their incorporation into routine monitoring.
Adsorption of PFASs by PAC. PAC can eectively remove
long-chain PFCAs and PFSAs, but its eectiveness decreases
with decreasing PFAS chain length.
24,25,29
It is unclear,
however, how the presence of ether group(s) in PFECAs
impacts adsorbability. After a contact time of 1 h, a PAC dose
of 100 mg/L achieved >80% removal of legacy PFCAs with
total carbon chain lengths of 7. At the same PAC dose,
removals were 95% for PFO4DA and 54% for PFO3OA, but
<40% for other PFECAs. Detailed removal percentage data as a
function of PAC contact time are shown in Figure S5. There
was no meaningful removal of PFMOBA or PFMOPrA, and the
variability shown in Figure S5 is most likely associated with
analytical variability. PFMOAA could not be quantied by the
analytical method used for these experiments; however, on the
basis of the observations that PFAS adsorption decreases with
decreasing carbon chain length and that PFECAs with one or
two more carbon atoms than PFMOAA (i.e., PFMOPrA and
PFMOBA) exhibited negligible removal (Figure 3), it is
expected that PFMOAA adsorption is also negligible under
the tested conditions.
To compare the anity of dierent PFASs for PAC, PFAS
removal percentages were plotted as a function of PFAS chain
length [the sum of carbon (including branched), ether oxygen,
and sulfur atoms] (Figure 3b). The adsorbability of both legacy
and emerging PFASs increased with increasing chain length.
PFSAs were more readily removed than PFCAs of matching
chain length, a result that agrees with those of previous
Figure 2. Fate of (a) legacy PFASs and PFPrOPrA and (b) PFECAs
through a full-scale water treatment plant. Because authentic standards
were not available for PFECAs other than PFPrOPrA, chromato-
graphic peak area counts are shown in panel b. PFPrOPrA data are
shown in both panels and highlighted with dashed ovals for reference.
Compounds with concentrations below the QLs were not plotted.
Environmental Science & Technology Letters Letter
DOI: 10.1021/acs.estlett.6b00398
Environ. Sci. Technol. Lett. XXXX, XXX, XXXXXX
C
studies.
24,25,29
PFECAs exhibited adsorbabilities lower than
those of PFCAs of the same chain length (e.g., PFMOBA <
PFHxA), suggesting that the replacement of a CF2group with
an ether oxygen atom decreases the anity of PFASs for PAC.
However, the replacement of additional CF2groups with ether
groups resulted in small or negligible anity changes among
the studied PFECAs (e.g., PFMOBA PFO2HxA, PFPrOPrA
~ PFO3OA). Alternatively, if only the number of peruorinated
carbons were considered as a basis of comparing adsorbability,
the interpretation would be dierent. In that case, with the
same number of peruorinated carbons, PFCAs have an anity
for PAC higher than that of monoether PFECAs (e.g., PFPeA >
PFMOBA) but an anity lower than that of multi-ether
PFECAs (e.g., PFPeA < PFO3OA).
To the best of our knowledge, this is the rst paper reporting
the behavior of recently identied PFECAs in water treatment
processes. We show that PFECAs dominated the PFAS
signature in a drinking water source downstream of a
uorochemical manufacturer and that PFECA removal by
many conventional and advanced treatment processes was
negligible. Our adsorption data further show that PFPrOPrA
(GenX) is less adsorbable than PFOA, which it is replacing.
Thus, PFPrOPrA presents a greater drinking water treatment
challenge than PFOA does. The detection of potentially high
levels of PFECAs, the continued presence of high levels of
legacy PFASs, and the diculty of eectively removing legacy
PFASs and PFECAs with many water treatment processes
suggest the need for broader discharge control and contaminant
monitoring.
ASSOCIATED CONTENT
*
SSupporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.estlett.6b00398.
Six tables, ve gures, information about PFASs,
analytical methods, and detailed results (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: msun8@uncc.edu. Phone: 704-687-1723.
ORCID
Mei Sun: 0000-0001-5854-9862
Notes
The views expressed in this article are those of the authors and
do not necessarily represent the views or policies of the
USEPA.
The authors declare no competing nancial interest.
ACKNOWLEDGMENTS
This research was supported by the National Science
Foundation (Grant 1550222), the Water Research Foundation
(Project 4344), and the North Carolina Urban Water
Consortium.
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Environmental Science & Technology Letters Letter
DOI: 10.1021/acs.estlett.6b00398
Environ. Sci. Technol. Lett. XXXX, XXX, XXXXXX
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DOI: 10.1021/acs.estlett.6b00398
Environ. Sci. Technol. Lett. XXXX, XXX, XXXXXX
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... PFOS and PFOA are listed as persistent organic pollutants (POPs) under the Stockholm Convention. In the EU, proposals to place the PFCAs on the candidate list of Substances of Very High Concern (SVHC), are ongoing, but to date, only PFOA, its salts, and related substances have been included [5,6]. These restrictions recently led to the replacement of LC PFASs with short-chain (SC) PFASs, whose toxicological properties are still under study but have raised significant concerns [5]. ...
... Up-to-date studies have shown that SC PFASs might be as persistent as LC PFASs, with different, but no less alarming, properties of concern; however, little evidence of their distribution in the environment is available yet [7,8]. This is, for example, the case with two compounds, GenX and C6O4, recently detected in rivers and drinking waters [6,[9][10][11][12]. GenX was introduced almost 10 years ago as a replacement for PFOA, and the occurrence of GenX in surface water at sampling sites located downstream of industrial areas has been recently documented [9,10]. ...
... GenX was introduced almost 10 years ago as a replacement for PFOA, and the occurrence of GenX in surface water at sampling sites located downstream of industrial areas has been recently documented [9,10]. Only two studies have documented the concentration of GenX in drinking water [6,10], but toxicological data are still incomplete and scarce [9]. Regarding C6O4, there are no published studies, and one of the main drawbacks in the detection of this compound is the unavailability of analytical standards. ...
Article
Full-text available
The availability of sensitive analytical methods to detect per- and polyfluoroalkyl substances (PFASs) in food of animal origin is fundamental for monitoring programs to collect data useful for improving risk assessment strategies. The present study aimed to develop and validate a fast and sensitive method for determining short and long-chain PFASs in meat (bovine, fish, and swine muscle), bovine liver, hen eggs, and cow’s milk to be easily applicable in routine analysis of food. A QuEChERS extraction and clean-up method in combination with liquid chromatography coupled to mass spectrometry (LC-MSMS) were used. The method resulted in good linearity (Pearson’s R > 0.99), low limits of detection (7.78–16.35 ng/kg, 8.26–34.01 ng/kg, 6.70–33.65 ng/kg, and 5.92–19.07 ng/kg for milk, liver, egg, and muscle, respectively), and appropriate limits of quantification (50 ng/kg for all compounds except for GenX and C6O4, where the limits of quantification were 100 ng/kg). Trueness and precision for all the tested levels met the acceptability criteria of 80–120% and ≤20%, respectively, regardless of the analyzed matrix. As to measurement uncertainty, it was <50% for all compound/matrix combinations. These results demonstrate the selectivity and sensitivity of the method for simultaneous trace detection and quantification of 14 PFASs in foods of animal origin, verified through the analysis of 63 food samples.
... Strynar et al. first identified several OCF 2 -type PFECA downstreams of the industrial effluent discharge from a fluorochemical production facility in 2015 and then detected in Cape Fear River and local finished drinking water with high levels. 28,64,65 Recently, Yao et al. also discovered the occurrence of novel PFECA in the Xiaoqing River and Taihu Lake that are nearby fluoropolymer facilities in China, indicating that OCF 2 -type PFECAs are widespread in the environment. 29,50 Some studies suggested that OCF 2 -type PFECA may be byproducts in the manufacture of HFPO-DA. ...
... 29,50 Some studies suggested that OCF 2 -type PFECA may be byproducts in the manufacture of HFPO-DA. 29, 65 We also monitored HFPO-DA in the manufactory and found that the DF and level were low, which indicated that PF4OPeA and PF5OHxA were unlikely to be caused by HFPO-DA. Overall, the emerging PF4OPeA and PF5OHxA are speculated to be generated from product research and development with unknown specific sources in this plant, which may migrate into the environment as emerging pollutants in the future. ...
... GenX was initially employed as a replacement for PFOA in the manufacturing of fluoropolymer resins and Teflon polytetrafluorethylene (DuPont Marketing 2010). Although the manufacturing uses of emerging PFAS are well-documented, the presence of GenX in aquatic systems was first reported in the Cape Fear River in 2012 (Sun et al. 2016). GenX has since been detected around the world including in Germany, the Netherlands, and China (Gebbink and van Leeuwen 2020;Heydebreck et al. 2015). ...
Article
With the stringent restrictions on long-chain per- and polyfluoroalkyl substances (PFASs), ether-PFASs are being widely used as alternatives. We estimated that the mega fluorochemical industrial park (FIP) in Shandong, China, had emitted a maximum of 5040 kg and 1026 kg of hexafluoropropylene oxides (HFPOs), and 7560 kg and 1890 kg of perfluorooctanoic acid (PFOA) to water and air during 2021. In the surface water, groundwater, outdoor dust, soil, tree leaf and bark collected in the vicinity of the FIP, PFOA was predominant, followed by HFPOs. The much higher percentage of HFPO dimer acid (HFPO-DA) in groundwater than in surface water verified that this compound was more mobile in porous media. The strong correlations between the main PFASs in outdoor dust and surface soil suggested that the soil PFASs were mainly derived from air deposition, particularly for HFPO trimer acid (HFPO-TA), which has a stronger binding affinity with particles than PFOA. High percentage of the hydroxylated product of 6:2 polyfluorinated ether sulfonic acid was observed in groundwater, implying reductive dechlorination might occur in groundwater. Strong correlations between PFASs in outdoor dust and those in tree leaf and bark magnified that tree could serve as a sampler to effectively monitor airborne PFASs. This study provides the first line of information about the discharge, transport, and fate of novel ether-PFASs in the multiple environmental media near a point source.
Article
Per- and polyfluoroalkyl substances (PFAS) comprise a diverse class of chemicals used in industrial processes, consumer products, and fire-fighting foams which have become environmental pollutants of concern due to their persistence, ubiquity, and associations with adverse human health outcomes, including in pregnant persons and their offspring. Multiple PFAS are associated with adverse liver outcomes in adult humans and toxicological models, but effects on the developing liver are not fully described. Here we performed transcriptomic analyses in the mouse to investigate the molecular mechanisms of hepatic toxicity in the dam and its fetus after exposure to two different PFAS, perfluorooctanoic acid (PFOA) and its replacement, hexafluoropropylene oxide-dimer acid (HFPO-DA, known as GenX). Pregnant CD-1 mice were exposed via oral gavage from embryonic day (E) 1.5–17.5 to PFOA (0, 1, or 5 mg/kg-d) or GenX (0, 2, or 10 mg/kg-d). Maternal and fetal liver RNA was isolated (N = 5 per dose/group) and the transcriptome analyzed by Affymetrix Array. Differentially expressed genes (DEG) and differentially enriched pathways (DEP) were obtained. DEG patterns were similar in maternal liver for 5 mg/kg PFOA, 2 mg/kg GenX, and 10 mg/kg GenX (R²: 0.46–0.66). DEG patterns were similar across all 4 dose groups in fetal liver (R²: 0.59–0.81). There were more DEGs in fetal liver compared to maternal liver at the low doses for both PFOA (fetal = 69, maternal = 8) and GenX (fetal = 154, maternal = 93). Upregulated DEPs identified across all groups included Fatty Acid Metabolism, Peroxisome, Oxidative Phosphorylation, Adipogenesis, and Bile Acid Metabolism. Transcriptome-phenotype correlation analyses demonstrated > 1000 maternal liver DEGs were significantly correlated with maternal relative liver weight (R² >0.92). These findings show shared biological pathways of liver toxicity for PFOA and GenX in maternal and fetal livers in CD-1 mice. The limited overlap in specific DEGs between the dam and fetus suggests the developing liver responds differently than the adult liver to these chemical stressors. This work helps define mechanisms of hepatic toxicity of two structurally unique PFAS and may help predict latent consequences of developmental exposure.
Article
Large fluoropolymer manufacturing facilities are major known sources of per- and polyfluoroalkyl substances (PFAS), many of which accumulate in groundwater, surface water, crops, wildlife, and people. Prior studies have measured high PFAS concentrations in groundwater, drinking water, soil, as well as dry and wet deposition near fluoropolymer facilities; however, much less is known about near-source PFAS air concentrations. We measured airborne PFAS on PM2.5 filters in close proximity to a major fluoropolymer manufacturing facility (Chemours' Fayetteville Works) located near Fayetteville, North Carolina, USA. Weekly PM2.5 filter samples collected over a six-month field campaign using high-volume air samplers at locations 3.7 km apart, north-northeast and south-southwest of the facility were analyzed for thirty-four targeted ionic PFAS species by liquid chromatography coupled to electrospray ionization tandem mass spectrometry. Twelve emerging and ten legacy PFAS compounds were detected. Thirteen PFAS were found at higher concentrations in these nearfield samples than at regional background sites, suggesting a local source for these compounds. Five emerging and five legacy PFAS compounds had maximum concentrations exceeding 1 pg m-3. PFBA, PFHxA, PFHxDA, PFOS, PMPA, NVHOS, PFO5DoA, and Nafion BP1 contributed the most to the total (legacy + emerging) PFAS concentration (86%). Six PFAS, specifically PFBA, PFOS, PFO5DoA, Nafion BP1, Nafion BP2, and Nafion BP4, provide a consistent representative profile of elevated species across the two sites (with detection frequency >50%). To our knowledge, this is the first study to report both legacy and emerging ionic PFAS in air in close proximity to a U.S. fluoropolymer manufacturing facility.
Article
High-resolution mass spectrometry was used to screen for emerging per- and polyfluorinated alkyl substances (PFAS) in precipitation samples collected in summer 2019 at seven sites in the United States. We previously quantified the concentration of ten PFAS in the rainwater samples using the method of isotopic dilution (Pike et al., 2021). Nine of these targeted analytes belonged to the U.S. Environmental Protection Agency Regional Screening Level list, herein referred to as EPA-monitored analytes. In this new work, we identify emerging PFAS compounds by liquid chromatography quadrupole time-of-flight mass spectrometry. Several emerging PFAS were detected across all samples, with the most prevalent compounds being C3-C8 hydrogen-substituted perfluorocarboxylic acids (H-PFCAs) and fluorotelomer carboxylic acids (FTCAs). Concentrations of emerging PFAS were in the 10-1000 ng L-1 range (approximately 1-2 orders of magnitude greater than EPA-monitored PFAS) at all sites except Wooster, OH, where concentrations were even higher, with a maximum estimated ΣPFAS of 16 400 ng L-1. The elevated levels of emerging PFAS in the Wooster samples were predominantly even and odd chain-length H-PFCAs and FTCAs comprised of complex mixtures of branched isomers. This unique composition did not match any known manufactured PFAS formulation reported to date, but it could represent thermally transformed by-products emitted by a local point source. Overall, the results indicate that PFAS outside of the standard analyte lists make up a significant and previously unappreciated fraction of contaminants in rainwater collected within the central U.S.-and potentially world-wide-especially in proximity to localized point sources.
Article
Treatment of large volumes of waters contaminated by per- and polyfluoroalkyl substances (PFAS) remains a challenge. This work presented a systematic study on PFAS removal by foam fractionation (FF). Experiments were conducted on both laboratory-spiked and environmental water samples containing PFASs. It is found that higher air flow, greater ionic strength, and addition of thickener boosted PFAS removal in the defoamed bottom solutions and intensified enrichment in the collected foam. FF treatments of a landfill leachate, a groundwater contaminated by aqueous film-forming foams, and a wastewater treatment plant effluent sample were evaluated. The removal of monitored PFAS reached above 70% for most PFASs, except the ones of short alkyl chains. PFAS concentrations in the final collected foams were up to over 500 × than that in the original samples. Analysis using high-resolution mass spectrometry revealed enrichment of non-target PFASs by FF. The results of this study demonstrate great effectiveness of FF in removing most PFASs from waters, producing low-volume, highly concentrated solutions of PFASs in all tested environmental samples.
Article
Recent reports demonstrate that technologies generating hydrated electrons (eaq−; e.g., UV-sulfite) are a promising strategy for destruction of per- and polyfluoroalkyl substances, but fundamental rate constants are lacking. This work examines the kinetics and mechanisms of eaq− reactions with ultra-short chain (C2–C4) fluorocarboxylates using experimental and theoretical approaches. Laser flash photolysis (LFP) was used to measure bimolecular rate constants (k2; M⁻¹ s⁻¹) for eaq− reactions with thirteen per-, and for the first time, polyfluorinated carboxylate structures. The measured k2 values varied widely from 5.26 × 10⁶ to 1.30 × 10⁸ M⁻¹s⁻¹, a large range considering the minor structural changes among the target compounds. Molecular descriptors calculated using density functional theory did not reveal correlation between k2 values and individual descriptors when considering the whole dataset, however, semiquantitative correlation manifests when grouping by similar possible initial reduction event such as electron attachment at the α-carbon versus β- or γ-carbons along the backbone. From this, it is postulated that fluorocarboxylate reduction by eaq− occurs via divergent mechanisms with the possibility of non-degradative pathways being prominent. These mechanistic insights provide rationale for contradictory trends between LFP-derived k2 values and apparent degradation rates recently reported in UV-sulfite constant irradiation treatment experiments.
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Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative chemicals that can be toxic at very low levels. Many of these compounds have unusual chemical properties that can have a large impact on analytical methods intended to quantitate them. When analyzing environmental samples, concentrating extraction eluents can greatly increase the sensitivity of PFAS extraction and analysis workflows. However, data on PFAS stability when evaporated under vacuum drying conditions are lacking. In this study two common sample preparation methods were replicated (methanol or methanolic ammonium hydroxide) to determine if PFAS material would undergo any observable loss during vacuum evaporation. Standards containing 49 different analytes from 7 different PFAS classes were evaporated to dryness under vacuum either with or without heat and reconstituted using one of two methods. It was found that recovery of some classes (e.g. PFSA, PFESA, FTS) was not greatly impacted by evaporation conditions or reconstitution method. Some analytes such as the very long chain PFCAs were not affected by evaporation conditions but saw drastic differences in recovery depending on the reconstitution method. Others analytes, for example PFSAms, experienced significant loss during evaporation that could not be mitigated by the chosen reconstitution method. This difference could be due to the number of fluorines present on the compound which correlated with a compound's hydrophobicity. Due to these findings, it is recommend that researchers consider PFAS class, chain length, and fluorine number when designing concentration and reconstitution protocols for PFAS to ensure conditions are optimal for the specific analytes of interest.
Article
Full-text available
Several perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been identified as chemicals of concern in the environment due to their persistence, global ubiquity, and classification as reproductive and developmental toxicants, endocrine disrupters, and possible carcinogens. Multiple PFASs are often found together in the environment due to product manufacturing methods and abiotic and biotic transformations. Treatment methods are needed to effectively sequester or destroy a variety of PFASs from groundwater, drinking water, and wastewater. This review presents a comprehensive summary of several categories of treatment approaches: (1) sorption using activated carbon, ion exchange, or other sorbents, (2) advanced oxidation processes, including electrochemical oxidation, photolysis, and photocatalysis, (3) advanced reduction processes using aqueous iodide or dithionite and sulfite, (4) thermal and nonthermal destruction, including incineration, sonochemical degradation, sub-or supercritical treatment, microwave-hydrothermal treatment, and high-voltage electric discharge, (5) microbial treatment, and (6) other treatment processes, including ozonation under alkaline conditions, permanganate oxidation, vitamin-B12 and Ti(III) citrate reductive defluorination, and ball milling. Discussion of each treatment technology, including background, mechanisms, advances, and effectiveness, will inform the development of cost-effective PFAS remediation strategies based on environmental parameters and applicable methodologies. Further optimization of current technologies to analyze and remove or destroy PFASs below regulatory guidelines is needed. Due to the stability of PFASs, a combination of multiple treatment technologies will likely be required to effectively address real-world complexities of PFAS mixtures and cocontaminants present in environmental matrices.
Article
Full-text available
Ammonium 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate, developed for use as a polymerization processing aid in the manufacture of fluoropolymers, was tested for its potential chronic toxicity and carcinogenicity in a 2-year oral dosing study in Sprague-Dawley rats. Male rats were given daily doses of either 0, 0.1, 1 or 50. mg/kg; females were given either 0, 1, 50 or 500. mg/kg. Body weights, food consumption and clinical signs were monitored daily; clinical pathology was conducted at designated intervals and animals were given a complete pathological evaluation after 12 months and 24 months of dosing. Normal survival was seen in all groups, no abnormal clinical signs were seen, and body weight gain was reduced only in female rats at 500. mg/kg. Both sexes at the high dose had mild decreases in red cell mass which were somewhat more pronounced in females. Clinical pathology indicative of liver injury was present in males that received 50. mg/kg and correlated with histomorphological liver changes that included both hypertrophic and degenerative/necrotic lesions. Similar histomorphological lesions were seen in the livers of females at 500. mg/kg. Previous shorter term toxicity studies have identified this chemical as a PPARα agonist and the finding of benign tumors of the liver, pancreas and/or testes in males at 50. mg/kg and females at 500. mg/kg is consistent with the rat response to peroxisome proliferators and is of questionable human relevance. Changes in the kidney, tongue, and stomach were observed only at the highest dose of 500. mg/kg in females. The no-observed-adverse-effect-level in this study lies between 1 and 50. mg/kg for males and between 50 and 500. mg/kg for females.
Article
Drinking water contamination with poly-and perfluoroalkyl substances (PFASs) poses risks to the developmental, immune, metabolic, and endocrine health of consumers. We present a spatial analysis of 2013−2015 national drinking water PFAS concentrations from the U.S. Environmental Protection Agency's (US EPA) third Unregu-lated Contaminant Monitoring Rule (UCMR3) program. The number of industrial sites that manufacture or use these compounds, the number of military fire training areas, and the number of wastewater treatment plants are all significant predictors of PFAS detection frequencies and concentrations in public water supplies. Among samples with detectable PFAS levels, each additional military site within a watershed's eight-digit hydrologic unit is associated with a 20% increase in PFHxS, a 10% increase in both PFHpA and PFOA, and a 35% increase in PFOS. The number of civilian airports with personnel trained in the use of aqueous film-forming foams is significantly associated with the detection of PFASs above the minimal reporting level. We find drinking water supplies for 6 million U.S. residents exceed US EPA's lifetime health advisory (70 ng/L) for PFOS and PFOA. Lower analytical reporting limits and additional sampling of smaller utilities serving <10000 individuals and private wells would greatly assist in further identifying PFAS contamination sources.
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The toxicological impact of traditional perfluoroalkyl chemicals has led to the elimination and restriction of these substances. However, many novel perfluoroalkyl alternatives remain unregulated and little is known about their potential effects on environmental and human health. Daily administration of two alternative perfluoroalkyl substances, HFPO2 and HFPO4 (1 mg kg−1 body weight), for 28 days resulted in hepatomegaly and hepatic histopathological injury in mice, particularly in the HFPO4 group. We generated and compared high-throughput RNA-sequencing data from hepatic tissues in control and treatment group mice to clarify the mechanism of HFPO2 and HFPO4 hepatotoxicity. We identified 146 (101 upregulated, 45 downregulated) and 1295 (716 upregulated, 579 downregulated) hepatic transcripts that exhibited statistically significant changes (fold change ≥2 or ≤0.5, false discovery rate < 0.05) after HFPO2 and HFPO4 treatment, respectively. Among them, 111 (82 upregulated, 29 downregulated) transcripts were changed in both groups, and lipid metabolism associated genes were dominant. Thus, similar to their popular predecessors, HFPO2 and HFPO4 exposure exerted hepatic effects, including hepatomegaly and injury, and altered lipid metabolism gene levels in the liver, though HFPO4 exerted greater hepatotoxicity than HFPO2. The unregulated use of these emerging perfluoroalkyl alternatives may affect environmental and human health, and their biological effects need further exploration. Copyright
Article
The fluoropolymer manufacturing industry is moving to alternative polymerization processing aid technologies with more favorable toxicological and environmental profiles as part of a commitment to curtail the use of long-chain perfluoroalkyl acids (PFAAs). To facilitate the environmental product stewardship assessment and premanufacture notification (PMN) process for a candidate replacement chemical, we conducted acute and chronic aquatic toxicity tests to evaluate the toxicity of ammonium 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate (C6HF11O3.H3N) or the acid form of the substance to the cladoceran, Daphnia magna, the green alga, Pseudokirchneriella subcapitata, and a number of freshwater fish species including the rainbow trout, Oncorhynchus mykiss, In addition, testing with the common carp, Cyprinus carpio, was conducted to determine the bioconcentration potential of the acid form of the compound. Based on the relevant criteria in current regulatory frameworks, the results of the aquatic toxicity and bioconcentration studies indicate the substance is of low concern for aquatic hazard and bioconcentration in aquatic organisms. Evaluation of environmental monitoring data in conjunction with the predicted no effect concentration (PNEC) based on the available data suggest low risk to aquatic organisms.
Article
Ammonium, 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate has been developed as a processing aid used in the manufacture of fluoropolymers. The absorption, distribution, elimination, and distribution (ADME) and kinetic behavior of this substance has been evaluated in rats, mice, and cynomolgus monkeys by oral and intravenous routes of exposure and studied in both plasma and urine. The test substance is rapidly and completely absorbed in both rats and mice and both in vivo and in vitro experiments indicate that it is not metabolized. The test substance is rapidly eliminated exclusively in the urine in both rats and mice, with rats eliminating it more quickly than mice (approximately 5h elimination half-life in rats, 20h half-life in mice). Pharmacokinetic analysis in monkeys, rats, and mice indicate rapid, biphasic elimination characterized by a very fast alpha phase and a slower beta phase. The beta phase does not contribute to potential accumulation after multiple dosing in rats or monkeys. Comparative pharmacokinetics in rats, mice, and monkeys indicates that the rat is more similar to the monkey and is therefore a more appropriate rodent model for pharmacokinetics in primates.
Article
Due to the lack of analytical standards the application of surrogate parameters for organofluorine detection in the aquatic environment is a complementary approach to single compound target analysis of perfluoroalkyl and polyfluoroalkyl chemicals (PFASs). The recently developed method adsorbable organically bound fluorine (AOF) is based on adsorption of organofluorine chemicals to activated carbon followed by combustion ion chromatography. This AOF method was further simplified to enable measurement of larger series of environmental samples. The limit of quantification (LOQ) was 0.77 μg/L F. The modified protocol was applied to 22 samples from German rivers, a municipal wastewater treatment plant (WWTP) effluent, and four groundwater samples from a fire-fighting training site. The WWTP effluent (AOF = 1.98 μg/L F) and only three river water samples (AOF between 0.88 μg/L F and 1.47 μg/L F) exceeded the LOQ. The AOF levels in a PFASs plume at a heavily contaminated site were in the range of 162 ± 3 μg/L F to 782 ± 43 μg/L F. In addition to AOF 17 PFASs were analyzed by high performance liquid chromatography-tandem mass spectrometry. 32–51% of AOF in the contaminated groundwater samples were explained by individual PFASs wheras in the surface waters more than 95% remained unknown. Organofluorine of two fluorinated pesticides, one pesticide metabolite and three fluorinated pharmaceuticals was recovered as AOF by >50% from all four tested water matrices. It is suggested that in the diffusely contaminated water bodies such fluorinated chemicals and not monitored PFASs contribute significantly to AOF.
Article
Recent scientific scrutiny and concerns over exposure, toxicity, and risk have led to international regulatory efforts resulting in the reduction or elimination of certain perfluorinated compounds from various products and waste streams. Some manufacturers have started producing shorter chain per- and polyfluorinated compounds to try to reduce the potential for bioaccumulation in humans and wildlife. Some of these new compounds contain central ether oxygens or other minor modifications of traditional perfluorinated structures. At present, there has been very limited information published on these "replacement chemistries" in the peer-reviewed literature. In this study we used a time-of-flight mass spectrometry detector (LC-ESI-TOFMS) to identify fluorinated compounds in natural waters collected from locations with historical perfluorinated compound contamination. Our workflow for discovery of chemicals included sequential sampling of surface water for identification of potential sources, nontargeted TOFMS analysis, molecular feature extraction (MFE) of samples, and evaluation of features unique to the sample with source inputs. Specifically, compounds were tentatively identified by (1) accurate mass determination of parent and/or related adducts and fragments from in-source collision-induced dissociation (CID), (2) in-depth evaluation of in-source adducts formed during analysis, and (3) confirmation with authentic standards when available. We observed groups of compounds in homologous series that differed by multiples of CF2 (m/z 49.9968) or CF2O (m/z 65.9917). Compounds in each series were chromatographically separated and had comparable fragments and adducts produced during analysis. We detected 12 novel perfluoroalkyl ether carboxylic and sulfonic acids in surface water in North Carolina, USA using this approach. A key piece of evidence was the discovery of accurate mass in-source n-mer formation (H(+) and Na(+)) differing by m/z 21.9819, corresponding to the mass difference between the protonated and sodiated dimers.
Article
The production and use of long-chain perfluoroalkyl substances (PFASs) must comply with national and international regulations. Driven by increasingly stringent regulations, their production has been outsourced to less regulated countries in Asia. In addition, the fluoropolymer industry started to use fluorinated alternatives, such as 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)propanoic acid (HFPO-DA). Between August 2013 and September 2014, we investigated the occurrence and distribution of HFPO-DA and legacy PFASs in surface waters of the following river/estuary systems: the Elbe and Rhine Rivers in Germany, the Rhine-Meuse delta in the Netherlands, and the Xiaoqing River in China. Distinct differences were revealed among the study areas; notably: the Chinese samples were highly polluted by an industrial point source discharging mainly perfluorooctanoic acid (PFOA). This particular point source resulted in concentrations more than 6000 times higher than an industrial point source observed in the Scheur River, where HFPO-DA was the dominant compound with a concentration of 73.1 ng/L. Moreover, HFPO-DA was detected in all samples along the coastline of the North Sea, indicating that the compound may be transported from the Rhine-Meuse-delta into the German Bight via the water current. To the best of our knowledge, the fluorinated alternative, HFPO-DA, was detected for the first time in surface waters of Germany and China.
Article
Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C4-C10 homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11-7500 ng/L) and PFPrS in all samples (19-63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging.