View source for Perfluoroalkyl and Polyfluoroalkyl Substances (PFASs)

Environmental releases of perfluoroalkyl and polyfluoroalkyl substances (PFASs) including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)have occurred at manufacturing facilities and in areas where aqueous film-forming foam (AFFF) was used to extinguish hydrocarbon fires. PFASs are suspected to cause adverse human health effects. They are highly stable in the environment and are typically removed from water supplies using granular activated carbon. There is a need for in situ treatment technologies and ex situ treatment methods that are more cost-effective. 

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'''Related Article(s):'''
*[[Soil & Groundwater Contaminants]]


'''CONTRIBUTOR(S):''' [[Dr. Rula Deeb]], [[Dr. Jennifer Field]], [[Elisabeth Hawley]], and [[Dr. Christopher Higgins]]


'''Key Resource(s):'''
*[[Media:USEPA-2014-Emerging_Contaminants_-_PFOS_and_PFOA_Fact_Sheet.pdf|U.S. EPA Emerging Contaminants - PFOS and PFOA Fact Sheet]]<ref name= "USEPA2014">U.S. Environmental Protection Agency, 2014. Emerging contaminants – perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Fact sheet. [[Media:USEPA-2014-Emerging_Contaminants_-_PFOS_and_PFOA_Fact_Sheet.pdf|March Fact Sheet]]</ref>

==Introduction==
Awareness of PFASs in the environment first emerged in the late 1990s following developments in analytical methods to detect ionized substances. Legal actions were taken against PFAS product manufacturing facilities in the West Virginia/Ohio River Valley<ref>Rich, N., 2016. The lawyer who became DuPont’s worst nightmare. The New York Times Magazine.</ref>. In 2000, the sole U.S. manufacturer of PFOS agreed to voluntarily discontinue production<ref>United States Environmental Protection Agency (U.S. EPA), 2000. EPA and 3M announce phase out of PFOS. News release dated Tuesday May 16. [https://yosemite.epa.gov/opa/admpress.nsf/0/33aa946e6cb11f35852568e1005246b4 U.S. EPA PFOS Phase Out Announcement]</ref>. The U.S. Environmental Protection Agency (EPA) issued provisional drinking water health advisories for PFOA and PFOS in 2009 and replaced these with health advisories in 2016<ref>United States Environmental Protection Agency (U.S. EPA), 2016. Drinking water health advisories for PFOA and PFOS. [https://www.epa.gov/ground-water-and-drinking-water/drinking-water-health-advisories-pfoa-and-pfos U.S. EPA Water Health Advisories - PFOA and PFOS]</ref>. Over the past five years, state regulators have required several former Air Force and Navy fire-fighter training areas to conduct site investigations for PFASs. SERDP/ESTCP research programs began funding related research in 2011 because they recognized the potential impact of this issue for the Department of Defense.

==Physical and Chemical Properties==
[[File:Deeb-Article 1-Figure 1.JPG|thumbnail|right|400px|Figure 1. a) Structure of a perfluoroalkyl substance, PFOS, compared with b) the structure of a polyfluoroalkyl substance, 6:2 fluorotelomer sulfonate (6:2 FTSA).]]
Although the environmental remediation industry initially used the term “perfluorinated compounds” (or PFCs), the more specific terminology of PFASs was recommended for consistent communication within the global scientific, regulatory, and industrial communities<ref>Buck, R.C., Franklin, J., Berger, U., Conder, J.M., Cousins, I.T., de Voogt, P., Jensen, A.A., Kannan, K., Mabury, S.A. and van Leeuwen, S.P., 2011. Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins. Integrated Environmental Assessment and Management, 7(4), 513-541. [http://dx.doi.org/10.1002/ieam.258 doi: 10.1002/ieam.258]</ref>. PFASs are fluorinated substances with a carbon chain structure. In perfluoroalkyl substances, each carbon atom in the chain is fully saturated with fluorine (carbon-fluorine bonds only), whereas the carbon chain in polyfluoroalkyl substances is mostly saturated with fluorine (carbon-fluorine bonds), but also contains [[wikipedia: Carbon–hydrogen bond | carbon-hydrogen bonds]] (Fig. 1). 

The most studied PFASs are PFOA and PFOS. Both have a hydrophobic carbon chain structure of eight carbons that are fully saturated with fluorine atoms (i.e., perfluoroalkyl substances) and a hydrophilic polar functional group. They are therefore “[[wikipedia: Hydrophile | amphiphilic]]” and associate with water and oils. This property made them useful ingredients in fire-fighting foams and other surfactant applications. In most groundwater environments, PFOS and PFOA are water-soluble anions. Their [[wikipedia: Surfactant | surfactant]] properties complicate the prediction of their physiochemical properties, such as partitioning coefficients. The strength of the carbon-fluorine bonds in PFASs creates extremely high chemical and thermal stabilities. Relevant properties of PFOS and PFOA are summarized below (Table 1<ref name= "USEPA2014"/>). 

[[File:Deeb-Article 1-Table 1.JPG|800px|thumbnail|center|Table 1. Physical and chemical properties of PFOS and PFOA<ref name= "USEPA2014"/>. <sup>1</sup>Note the salt form of PFOA is more likely to be environmentally and toxicological relevant; however, its properties are not available. Abbreviations: g/mol = grams per mole; mg/L = milligrams per liter; <sup>o</sup>C = degree Celsius; mm Hg = millimeters of mercury; atm-m<sup>3</sup>/mol = atmosphere-cubic meters per mole. <sup>2</sup>Water solubility in purified water. <sup>3</sup>Water solubility in fresh water. <sup>4</sup>Water solubility in filtered seawater. <sup>5</sup>Extrapolation from measurement. <sup>6</sup>Estimated based on anion properties. <sup>7</sup>The atmospheric half-life value identified for PFOA was estimated based on available data determined from short study periods.]]

==Environmental Concern==
Perfluorinated substances are very stable, do not biodegrade, and are found throughout the environment globally. In contrast, the presence of carbon-hydrogen groups in polyfluoroalkyl substances makes these compounds easier to partially degrade, forming shorter-chain perfluoroalkyl compounds. Trace amounts of perfluorinated substances have been detected at remote locations like the Arctic, far from potential point sources<ref>Young, C.J., Furdui, V.I., Franklin, J., Koerner, R.M., Muir, D.C. and Mabury, S.A., 2007. Perfluorinated acids in arctic snow: new evidence for atmospheric formation. Environmental Science & Technology, 41(10), 3455-3461. [http://dx.doi.org/10.1021/es0626234 doi: 10.1021/es0626234]</ref>. Other studies have shown that long-chain perfluorinated substances bioaccumulate and biomagnify in wildlife<ref>Conder, J.M., Hoke, R.A., Wolf, W.D., Russell, M.H. and Buck, R.C., 2008. Are PFCAs bioaccumulative? A critical review and comparison with regulatory criteria and persistent lipophilic compounds. Environmental Science & Technology, 42(4), 995-1003. [http://dx.doi.org/10.1021/es070895g doi: 10.1021/es070895g]</ref>. Because of this, higher trophic wildlife including fish and birds can be particularly susceptible<ref>Sinclair, E., Mayack, D.T., Roblee, K., Yamashita, N. and Kannan, K., 2006. Occurrence of perfluoroalkyl surfactants in water, fish, and birds from New York State. Archives of Environmental Contamination and Toxicology, 50(3), pp.398-410. [http://dx.doi.org/10.1007/s00244-005-1188-z doi: 10.1007/s00244-005-1188-z]</ref>. The Dutch National Institute for Public Health and the Environment calculated a maximum permissible concentration for PFOS of 0.65 nanograms per liter (ng/L) for fresh water, based on human consumption of fish<ref name= "USEPA2014"/>.

PFASs typically associate with the liver, proteins, and the blood stream. In humans, they have a half-life in the range of 2 to 9 years<ref name= "USEPA2014"/>. Toxicological studies of PFOA indicate potential developmental or reproductive effects<ref name= "USEPA2014"/>. Both PFOA and PFOS are suspected carcinogens, but their carcinogenicity remains to be classified by the U.S. EPA<ref name= "USEPA2014"/>. The International Agency for Research on Cancer (IARC) has classified PFOA as a Group 2B carcinogen, i.e., possibly carcinogenic to humans<ref>Benbrahim-Tallaa, L., Lauby-Secretan, B. Loomis, D., Guyton, K.Z., Grosse, Y., Bouvard, F. El Ghissassi, V., Guha, N., Mattock, H., Straif, K., 2014. Carcinogenicity of perfluorooctanoic acid, tetrafluoroethylene, dichloromethane, 1,2-dichloropropane, and 1,3-propane sultone. The Lancet Oncology, 15 (9), 924-925. [http://dx.doi.org/10.1016/s1470-2045(14)70316-x doi: 10.1016/S1470-2045(14)70316-X]</ref><ref>International Agency for Research on Cancer (IARC), 2016. Monographs on the evaluation of carcinogenic risks to humans. Lists of Classifications, Volumes 1 to 116. [[Media:IARC-2016-Monographs_on_the_eval_of_carcinogenic_risks_to_humans_List_of_Classifications.pdf|List of Classifications.pdf]]</ref>. The U.S. EPA published draft reference doses of 30 ng/kg*day PFOS and 20 ng/kg*day PFOA (based on non-cancer hazard). For site remediation, drinking water ingestion, fish consumption, dermal contact with water, and (accidental) ingestion or contact with contaminated soil are the exposure pathways of concern.

==Uses and Potential Sources to the Environment==
Due to their unique properties, many PFASs function as surfactants or components of surface coatings. They are stain-resistant, heat-resistant, and are useful for coating surfaces that are in contact with acids or bases<ref>Krafft, M.P. and Riess, J.G., 2015. Selected physicochemical aspects of poly-and perfluoroalkylated substances relevant to performance, environment and sustainability - Part one. Chemosphere, 129, 4-19. [http://dx.doi.org/10.1016/j.chemosphere.2014.08.039 doi: 10.1016/j.chemosphere.2014.08.039]</ref><ref name= "USEPA2014"/>. Thus, they are used widely by a number of industries, including carpet, textile and leather production, chromium plating, photography, photolithography, semi-conductor manufacturing, coating additives, cleaning products, and insecticides<ref name= "USEPA2014"/>. PFASs are also found in a variety of consumer products including food paper and packaging, furnishings, waterproof clothing, and cosmetics<ref>Birnbaum, L.S. and Grandjean, P., 2015. Alternatives to PFASs: Perspectives on the Science. Environmental Health Perspectives, 123(5), A104-A105. [http://dx.doi.org/10.1289/ehp.1509944 doi: 10.1289/ehp.1509944]</ref>. The presence of PFASs in consumer products has created an urban background concentration in stormwater, wastewater treatment plant influent<ref>Houtz, E.F., 2013. Oxidative measurement of perfluoroalkyl acid precursors: Implications for urban runoff management and remediation of AFFF-contaminated groundwater and soil. Ph.D. Dissertation. Available online at http://escholarship.org/uc/item/4jq0v5qp</ref>, and landfill leachate<ref>Lang, J.R., Allred, B.M., Peaslee, G.F., Field, J.A. and Barlaz, M.A., 2016. Release of Per-and Polyfluoroalkyl Substances (PFASs) from Carpet and Clothing in Model Anaerobic Landfill Reactors. Environmental Science & Technology, 50(10), 5024-5032. [http://dx.doi.org/10.1021/acs.est.5b06237 doi: 10.1021/acs.est.5b06237]</ref>. 

One of the most widely known sources of PFASs is AFFF, which was used in large quantities in the environment on fires, at fire-fighting training areas, during the activation of fire suppression systems in airplane hangars and other buildings, and accidentally through AFFF storage, transport, and day-to-day handling. AFFF was routinely used at military sites, airports, and refineries. Formulations are proprietary and the composition of AFFF varies with the manufacturer. However, AFFF typically consists of water (60-93%), solvents such as butyl carbitol (3-25%), hydrocarbon surfactants (1-12%), one or more PFASs, and other compounds (e.g., corrosion inhibitors, electrolytes<ref>Conder, J., Deeb, R.A., Field, J.A. and Higgins, C.P., 2016. GRACast: Frequently asked questions on Per- and Polyfluoroalkyl Substances (PFASs). Presented on July 6. [[Media:Conder-2008-GRACast_Frequently_asked_questions_on_PFASs.pdf|FAQs]]</ref>). PFAS signatures of a variety of different AFFF formulations can assist in forensic identification of PFAS sources<ref>Backe, W.J., Day, T.C. and Field, J.A., 2013. Zwitterionic, cationic, and anionic fluorinated chemicals in aqueous film forming foam formulations and groundwater from US military bases by nonaqueous large-volume injection HPLC-MS/MS. Environmental Science & Technology, 47(10), 5226-5234. [http://dx.doi.org/10.1021/es3034999 doi: 10.1021/es3034999]</ref><ref>Place, B.J. and Field, J.A., 2012. Identification of novel fluorochemicals in aqueous film-forming foams used by the U.S. military. Environmental Science & Technology, 46(13), 7120-7127. [http://dx.doi.org/10.1021/es301465n doi: 10.1021/es301465n]</ref>.

==Regulation==
Final regulations have not yet been promulgated for PFAS; current criteria for PFAS are typically in the form of guidance or advisory levels (Table 2). The U.S. EPA recently developed Drinking Water Health Advisory levels for PFOA and PFOS, replacing previously published provisional values. Several states including Minnesota, Maine and New Jersey, have published screening values or interim criteria for one or more PFASs including PFOS, PFOA, perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA) and perfluorononanoic acid (PFNA) (Table 2). Drinking water, groundwater, and soil criteria in the European Union was recently published in a summary report<ref>Concawe, 2016. Environmental fate and effects of poly- and perfluoroalkyl substances (PFAS). Report no. 8/16. [[Media:Concawe-2016-Environmental_fate_and_effects_of_PFAS.pdf|Report pdf]]</ref>. 

Other regulatory actions have restricted the use and production of PFASs. PFOS was added to list of chemicals under the Stockholm Convention on persistent organic pollutants in 2009. Nearly all use of PFOS is therefore banned in Europe, with some exemptions. Substances or mixtures may not contain PFOS above 0.001% by weight (EU 757/2010). In the U.S., because PFOS manufacturing was voluntarily phased out in 2002, AFFF containing PFOS is no longer manufactured. The U.S. military and others still have large quantities of stockpiled AFFF containing PFOS, although its use is discouraged. 

{| class="wikitable"
|-
!style="background-color:#CEE0F2;"| REGULATORY AGENCY!!style="background-color:#CEE0F2;"|  DESCRIPTION !!style="background-color:#CEE0F2;"|  PFOS!! style="background-color:#CEE0F2;"| PFOA!!style="background-color:#CEE0F2;"|  PFBS!! style="background-color:#CEE0F2;"| PFBA!! style="background-color:#CEE0F2;"| PFNA
|-
| colspan="12" style="color:black;text-align:center;"|'''DRINKING WATER (µg/L)'''
|-
| U.S. EPA || [[Media:Deeb-Article_1-Table_2_L1-Drinking_water_health_advisories.pdf|Drinking Water Health Advisories]] ||style="text-align:center;"|0.07||style="text-align:center;"|0.07 || || || 
|-
|Health Canada|| [[Media:Deeb-Article_1-Table_2-L2-Drinking_water_screening_values.pdf|Drinking Water Screening Values]]||style="text-align:center;"| 0.6||style="text-align:center;"| 0.2||style="text-align:center;"| 15||style="text-align:center;"| 30||style="text-align:center;"| 0.2
|-
|Maine Department of Environmental Protection|| [https://www1.maine.gov/dhhs/mecdc/environmental-health/eohp/wells/documents/pfoameg.pdf Maximum Exposure Guideline]||  ||style="text-align:center;"| 0.1 || || || 
|-
| Michigan Department of Environmental Quality|| [http://www.michigan.gov/documents/deq/wrd-swas-rule57_372470_7.pdf Drinking Water Surface Water Quality Value] ||style="text-align:center;"| 0.011||style="text-align:center;"| 0.42|| || || 
|-
|New Jersey Department of Environmental Protection || [http://www.nj.gov/dep/watersupply/pdf/pfoa_dwguidance.pdf Preliminary Health-Based Guidance Value]|| ||style="text-align:center;"| 0.04 || || || 
|-
|New Jersey Department of Environmental Protection ||[[Media:Deeb-Article_1-Table_2-L6-Dev_of_MCL_recommendations_for_PFOA_and_PFOS.pdf|Development of MCL Recommendations for PFOA and PFOS are Currently in Progress]]|| ||style="text-align:center;"| 0.04|| || || 
|-
|New Jersey Department of Environmental Protection|| [[Media:Deeb-Article_1-Table_2-L7-Health-Based_Maximum_Contaminant_Level_MCL.pdf|Health-Based Maximum Contaminant Level (MCL) Recommendation]]|| || || || ||style="text-align:center;"| 0.013
|-
|Vermont Department of Health|| [http://dec.vermont.gov/ Drinking Water Health Advisory Level]|| ||style="text-align:center;"| 0.02|| || || 
|-
| colspan="12" style="color:black;text-align:center;"|'''GROUNDWATER (µg/L)'''
|-
|Minnesota Department of Health|| [http://www.health.state.mn.us/divs/eh/risk/guidance/gw/table.html Health Risk Limit for Groundwater] ||style="text-align:center;"| 0.3||style="text-align:center;"| 0.3 ||style="text-align:center;"| 7 ||style="text-align:center;"| 7 || 
|-
|Illinois Environmental Protection Agency|| [[Media:Deeb-Article_1-Table_2-L10-Provisional_Groundwater_Remediaton_Objectives_Class_I_Groundwater.pdf|Provisional Groundwater Remediation Objectives, Class I Groundwater]]||style="text-align:center;"| 0.2||style="text-align:center;"| 0.4|| || || 
|-
|Illinois Environmental Protection Agency|| [[Media:Deeb-Article_1-Table_2-L11-Provisional_Groundwater_Remediaton_Objectives_Class_II_Groundwater_.pdf|Provisional Groundwater Remediation Objectives, Class II Groundwater]]|| style="text-align:center;"|0.2|| style="text-align:center;"|0.2|| || || 
|-
|North Carolina Department of Environmental Quality||[http://deq.nc.gov/about/divisions/air-quality/science-advisory-board-toxic-air-pollutants/ncsab-aal-recommendations Interim Maximum Allowable Concentration] || || style="text-align:center;"|1.0|| || || 
|-
|New Jersey Department of Environmental Protection|| [[Media:Deeb-Article_1-Table_2-L13-Interim_specific_groundwatr_quality_criterion_fact_sheet.pdf|Interim Specific Ground Water Quality Criterion]]|| || || || ||style="text-align:center;"| 0.01
|-
|Maine Department of Environmental Protection|| [http://www.maine.gov/dep/spills/publications/guidance/rags/ME-RAGS-Revised-Final_020516.pdf Remedial Action Guidelines for Residential Groundwater] ||style="text-align:center;"| 0.06||style="text-align:center;"| 0.1|| || || 
|-
|Michigan Department of Environmental Quality|| [[Media:Deeb-Article_1-Table_2-L15-Groundwater_residential_generic_cleanup_criteria_and_screening_levels_.pdf|Groundwater Residential Generic Cleanup Criteria and Screening Levels]]|| style="text-align:center;"|0.12||style="text-align:center;"| 0.089|| || || 
|-
| Michigan Department of Environmental Quality|| [[Media:Deeb-Article_1-Table_2-L16-Groundwater_nonresidential_generic_cleanup_criteria_and_screening_levels.pdf|Groundwater Nonresidential Generic Cleanup Criteria and Screening Levels]]|| style="text-align:center;"|0.5||style="text-align:center;"| 0.28 || || || 
|-
|Texas Commission on Environmental Quality Texas Risk Reduction Program|| [http://www.tceq.texas.gov/assets/public/remediation/trrp/pcls2014.xlsx Protective Concentration Levels for 16 PFASs for Several Different Exposure Scenarios (Groundwater)]|| || || || || 
|-
|Alaska Department of Environmental Conservation|| [http://dec.alaska.gov/spar/csp/guidance_forms/docs/Interim%20Tech%20Memo%20-%20DEC%20cleanup%20levels%20and%20EPA%20HAs%20for%20PFOS%20and%20PFOA%20August%202016%20Final.pdf Cleanup Levels]||style="text-align:center;" |0.4||style="text-align:center;"| 0.4|| || || 
|-
| colspan="12" style="color:black;text-align:center;"|'''SOIL (mg/kg)'''
|-
| U.S. EPA Region 4|| [[Media:Deeb-Article_1-Table_2-L18-Residential_soil_screening_levels.pdf|Residential Soil Screening Level]]|| style="text-align:center;"|6|| style="text-align:center;"|16|| || || 
|-
|Minnesota Pollution Control Agency|| [[Media:Deeb-Article_1-Table_2-L19-Industrial_soil_reference_value.xlsx|Industrial Soil Reference Value (.xlsx)]]||style="text-align:center;"| 14||style="text-align:center;"| 13|| ||style="text-align:center;"| 500|| 
|-
|Minnesota Pollution Control Agency|| [[Media:Deeb-Article_1-Table_2-L20-Residential_soil_reference_value.xlsx|Residential Soil Reference Value(.xlsx)]]||style="text-align:center;"| 2.1|| style="text-align:center;"|2.1|| ||style="text-align:center;"| 77|| 
|-
|Minnesota Pollution Control Agency|| [[Media:Deeb-Article_1-Table_2-L21-Recreational_soil_reference_value.xlsx|Recreational Soil Reference Value(.xlsx)]]|| style="text-align:center;"|2.6||style="text-align:center;"| 2.5|| ||style="text-align:center;"| 95|| 
|-
|Maine Department of Environmental Protection||[[Media:Deeb-Article_1-Table_2-L22-ME-Remedial_Action_guidelines.pdf|Remedial Action Guidelines for different exposure scenarios]]||style="text-align:center;"|11-82|| || || ||
|-
|Texas Commission on Environmental Quality Texas Risk Reduction Program ||[http://www.tceq.texas.gov/assets/public/remediation/trrp/pcls2014.xlsx Protective Concentration Levels for 16 PFASs for Several Different Exposure Scenarios (Soil)] || || || || ||
|-
|Alaska Department of Environmental Conservation|| [http://dec.alaska.gov/spar/csp/guidance_forms/docs/Interim%20Tech%20Memo%20-%20DEC%20cleanup%20levels%20and%20EPA%20HAs%20for%20PFOS%20and%20PFOA%20August%202016%20Final.pdf Cleanup Level, Arctic Zone]||style="text-align:center;" |2.2||style="text-align:center;"| 2.2|| || || 
|-
|Alaska Department of Environmental Conservation|| [http://dec.alaska.gov/spar/csp/guidance_forms/docs/Interim%20Tech%20Memo%20-%20DEC%20cleanup%20levels%20and%20EPA%20HAs%20for%20PFOS%20and%20PFOA%20August%202016%20Final.pdf Cleanup Level, Under 40' Zone]||style="text-align:center;" |1.6||style="text-align:center;"| 1.6|| || || 
|-
|Alaska Department of Environmental Conservation|| [http://dec.alaska.gov/spar/csp/guidance_forms/docs/Interim%20Tech%20Memo%20-%20DEC%20cleanup%20levels%20and%20EPA%20HAs%20for%20PFOS%20and%20PFOA%20August%202016%20Final.pdf Cleanup Level, Over 40' Zone]||style="text-align:center;" |1.3||style="text-align:center;"| 1.3|| || || 
|-
|Alaska Department of Environmental Conservation|| [http://dec.alaska.gov/spar/csp/guidance_forms/docs/Interim%20Tech%20Memo%20-%20DEC%20cleanup%20levels%20and%20EPA%20HAs%20for%20PFOS%20and%20PFOA%20August%202016%20Final.pdf Cleanup Level, Migration to Groundwater (MTGW)]||style="text-align:center;" |0.0030||style="text-align:center;"| 0.0017|| || || 
|-
| colspan="10" style="color:black;text-align;font-size:90%;left;"|Table 2. Summary of PFAS Regulatory Criteria. Regulatory criteria for PFAS are still evolving relatively quickly. Please check the hyperlinked reference to confirm that the regulatory criteria listed in the table are up to date before using this information. Some states have PFAS regulatory values for groundwater as a result of consent agreements (e.g., both West Virginia and Ohio signed a [https://yosemite.epa.gov/opa/admpress.nsf/a5792a626c8dac098525735900400c2d/35ab2180c4ed47698525757700575dc2!OpenDocument consent agreement] with DuPont listing 0.4 µg/L as a precautionary site-specific action level for PFOA). Other states (e.g., Delaware, New Hampshire, New York) have adopted U.S. EPA provisional health advisory levels for PFOS and PFOA in several water systems. Pennsylvania has investigated PFOS contamination associated with two contaminated wells identified through EPA Unregulated Contaminant Monitoring Rule program. Alabama has also addressed PFAS contamination on a site-specific basis. Alaska has conducted sampling and monitoring for PFAS at multiple sites.
|}

==Sampling and Analytical Methods==
Because PFASs are present in several common consumer items, care should be taken during sampling to eliminate contact with other potential sources of PFASs. Most standard operating procedures and work plans advise avoiding the use of polytetrafluoroethylene-based (e.g., Teflon) components including tubing and lined sample bottle caps. Some also instruct samplers not to wear waterproof jackets or other outerwear with a waterproof coating, and to avoid handling packaged foods that may contain fluorotelomer-based chemicals to increase non-stick properties. Due to the affinity of PFASs for the air-water interface and the wettability of glass, sample bottles are typically polypropylene or high-density polyethylene. 

Most commercial laboratories use a modified version of U.S. EPA Method 537 for the analysis of PFASs in drinking water. This method consists of solid phase extraction and liquid chromatography with tandem mass spectrometry. Analytes include PFOS, PFOA, and typically 12 other PFASs (mostly perfluorocarboxylic acids and perfluorosulfonic acids) of varying carbon chain length. Specialty laboratories have modified this analytical method for matrices other than drinking water, to better recover shorter-chain compounds, or achieve lower detection limits.

Commercial laboratories that can quantify an even broader suite of PFASs (e.g., those known to be present in AFFF formulations and degrade to form PFOA and PFOS) are rare. An analytical method to detect several families of PFAS precursors<ref>TerMaath, S., J. Field and C. Higgins, 2016. Per- and polyfluoroalkyl substances (PFASs): Analytical and characterization frontiers. [https://www.serdp-estcp.org/Tools-and-Training/Webinar-Series/01-28-2016 Webinar Series]</ref>. There is also the Total Oxidizable Precursor (TOP) assay, a bulk measurement of precursors that can be oxidized to perfluorocarboxylates<ref>Houtz, E.F., Higgins, C.P., Field, J.A. and Sedlak, D.L., 2013. Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil. Environmental Science & Technology, 47(15), 8187-8195. [http://dx.doi.org/10.1021/es4018877 doi: 10.1021/es4018877]</ref>. Other approaches to quantify the total amount of organic fluorine in water samples include particle induced gamma-ray emission (PIGE) and absorbable organic fluorine (AOF)<ref>Willach, S., Brauch, H.J. and Lange, F.T., 2016. Contribution of selected perfluoroalkyl and polyfluoroalkyl substances to the adsorbable organically bound fluorine in German rivers and in a highly contaminated groundwater. Chemosphere, 145, 342-350. [http://dx.doi.org/10.1016/j.chemosphere.2015.11.113 doi:10.1016/j.chemosphere.2015.11.113]</ref>.

The cost-effectiveness of high-resolution site characterization methods for PFASs is currently limited due to the lack of a reliable analytical method that can be used in the field as a screening method. Several research groups have attempted to design a field-ready mobile analytical method. For example, United Science LLC is developing ion selective electrodes to measure PFOS at ng/L levels<ref>U.S. Environmental Protection Agency, 2015. Final report: field deployable PFCs sensors for contaminated soil screening. EPA contract number EPD14012. [https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/10230/report/F Report pdf]</ref>. Geosyntec Consultants and Eurofins Eaton Analytical are developing a mobile field unit for screening PFOS and other PFASs to ng/L levels<ref>Deeb, R., Chambon, J., Haghani, A., and Eaton, A., 2016. Development and testing of an analytical method for real time measurement of polyfluoroalkyl and perfluoroalkyl substances (PFAS). Presented at the Battelle Chlorinated Conference, Palm Springs, CA.</ref>. 
  
==Fate and Transport==
The following summarize some key concepts for PFAS fate and transport:

*'''Sorption''': Both PFOA and PFOS are anions at typical environmental pH values, but still exhibit strong interactions with solid-phase organic carbon. For this reason, the f<sub>oc</sub>-K<sub>oc</sub> method for predicting sorption is generally appropriate<ref>Higgins, C.P., and Luthy, R.G., 2006. Sorption of perfluorinated surfactants on sediments. Environmental Science & Technology, 40(23), 7251-7256. [http://dx.doi.org/10.1021/es061000n doi: 10.1021/es061000n]</ref>, though this has not been confirmed for all PFASs. Interactions with mineral phases, particularly ferric oxide materials, may be important in low f f<sub>oc</sub> materials<ref name= "Ferrey2012">Ferrey, M.L., Wilson, J.T., Adair, C., Su, C., Fine, D.D., Liu, X. and Washington, J.W., 2012. Behavior and fate of PFOA and PFOS in sandy aquifer sediment. Groundwater Monitoring & Remediation, 32(4), 63-71. [http://dx.doi.org/10.1111/j.1745-6592.2012.01395.x  doi: 10.1111/j.1745-6592.2012.01395.x]</ref><ref>Johnson, R.L., Anschutz, A.J., Smolen, J.M., Simcik, M.F. and Penn, R.L., 2007. The adsorption of perfluorooctane sulfonate onto sand, clay, and iron oxide surfaces. Journal of Chemical & Engineering Data, 52(4), 1165-1170. [http://dx.doi.org/10.1021/je060285g doi: 10.1021/je060285g]</ref>. At present, empirical site-specific sorption estimates are recommended to accurately predict PFAS mobility<ref name= "Ferrey2012"/>.

*'''Biotransformation''': PFOS, PFOA, and analogous compounds of varying chain lengths are persistent in the environment and do not readily biodegrade. Polyfluorinated forms partially degrade in the environment<ref name= "Tseng2014">Tseng, N., Wang, N., Szostek, B. and Mahendra, S., 2014. Biotransformation of 6: 2 fluorotelomer alcohol (6: 2 FTOH) by a wood-rotting fungus. Environmental Science & Technology, 48(7), 4012-4020. [http://dx.doi.org/10.1021/es4057483 doi:10.1021/es4057483]</ref><ref>Harding-Marjanovic, K.C., Houtz, E.F., Yi, S., Field, J.A., Sedlak, D.L. and Alvarez-Cohen, L., 2015. Aerobic biotransformation of fluorotelomer thioether amido sulfonate (Lodyne) in AFFF-amended microcosms. Environmental Science & Technology, 49(13), pp.7666-7674. [http://dx.doi.org/10.1021/acs.est.5b01219  doi: 10.1021/acs.est.5b01219]</ref>, particularly if conditions (e.g., dissolved oxygen concentrations, pH) have been altered to treat co-contaminants<ref name= "McGuire2014">McGuire, M.E., Schaefer, C., Richards, T., Backe, W.J., Field, J.A., Houtz, E., Sedlak, D.L., Guelfo, J.L., Wunsch, A. and Higgins, C.P., 2014. Evidence of remediation-induced alteration of subsurface poly-and perfluoroalkyl substance distribution at a former firefighter training area. Environmental Science & Technology, 48(12), 6644-6652. [http://dx.doi.org/10.1021/es5006187 doi: 10.1021/es5006187]</ref>. However, degradation products are often more recalcitrant – degradable polyfluorinated forms are precursors for PFOA, PFOS and their homologs. In contrast, fungal degradation has been shown to result in lower production of perfluorocarboxylic acids<ref name= "Tseng2014"/>. 

*'''Other effects of microbes''': Some microbes, in the presence of PFOA, aggregate and produce extracellular polymeric substances<ref>Weathers, T.S., Higgins, C.P. and Sharp, J.O., 2015. Enhanced biofilm production by a toluene-degrading rhodococcus observed after exposure to perfluoroalkyl acids. Environmental Science & Technology, 49(9), 5458-5466. [http://dx.doi.org/10.1021/es5060034 doi: 10.1021/es5060034]</ref>. Microbes also facilitate PFAS leaching under methanogenic conditions common at municipal solid waste landfills<ref>Allred, B.M., Lang, J.R., Barlaz, M.A. and Field, J.A., 2015. Physical and biological release of poly-and perfluoroalkyl substances (PFASs) from municipal solid waste in anaerobic model landfill reactors. Environmental Science & Technology, 49(13), 7648-7656. [http://dx.doi.org/10.1021/acs.est.5b01040 doi: 10.1021/acs.est.5b01040]</ref>. Depending on the conditions, microbial activity may therefore enhance the mobility of compounds like PFOS and PFOA or hypothetically have the opposite effect by increasing sorption. 

*'''Effect of co-contaminants and co-contaminant remediation strategies''': Interactions between PFASs and non-aqueous phase liquids can retard PFAS migration<ref>Guelfo, J. 2013. Subsurface fate and transport of poly- and perfluoroalkyl substances. Doctor of Philosophy Thesis, Colorado School of Mines. [[Media:Guelfo-2013-Subsuface_fate_and_transport_of_Poly-and_perfluoroalkyl_substances.pdf|Thesis]]</ref>. TCE dechlorination can be inhibited by PFASs<ref>Weathers, T.S., Harding-Marjanovic, K., Higgins, C.P., Alvarez-Cohen, L. and Sharp, J.O., 2015. Perfluoroalkyl acids inhibit reductive dechlorination of trichloroethene by repressing dehalococcoides. Environmental Science & Technology, 50(1), 240-248. [http://dx.doi.org/10.1021/acs.est.5b04854 doi: 10.1021/acs.est.5b04854]</ref> and that inhibition depends both on PFAS structure and<ref>Harding-Marjanovic, K.C., Yi, S., Weathers, T.S., Sharp, J.O., Sedlak, D.L. and Alvarez-Cohen, L., 2016. Effects of Aqueous Film-Forming Foams (AFFFs) on Trichloroethene (TCE) Dechlorination by a Dehalococcoides mccartyi-Containing Microbial Community. Environmental Science & Technology, 50(7), 3352-3361. [http://dx.doi.org/10.1021/acs.est.5b04773 doi: 10.1021/acs.est.5b04773]</ref>. PFAS precursors degraded to form PFOA and other PFAS at a former fire-fighting training area at Ellsworth Air Force Base, where several remediation methods, including soil vapor extraction, groundwater pump and treat, bioventing, and oxygen infusion were used to treat co-contaminants<ref name= "McGuire2014"/>. 

==Soil and Groundwater Remediation==
Due to the chemical and thermal stability of PFASs and the complexity of PFAS mixtures, soil and groundwater remediation is challenging and costly. Research is still ongoing to develop effective remedial strategies. 

For soil, it is common to evaluate several management options: 1) treatment and/or direct on-site reuse, 2) temporary on-site storage, and 3) off-site disposal to a soil processing or treatment facility, licensed landfill, or incinerator. Soil treatment products are commercially available to stabilize PFASs and decrease leaching. Criteria for stabilizing or treating soils prior to landfill disposal are highly site specific. Other technologies that have been considered for removing PFASs from soil include soil washing and incineration. 

For groundwater, management options include the following: 1) in situ treatment, 2) ex situ treatment and/or reuse, aquifer reinjection, or discharge to surface water, stormwater, or sewer, 3) temporary on-site storage, and 4) off-site disposal to a hazardous waste treatment and disposal facility. The most common remediation approach is to use pump-and-treat with granular activated carbon followed by off-site incineration of the spent activated carbon. This technology has been used for years at full scale<ref name= "Appleman2014">Appleman, T.D., Higgins, C.P., Quinones, O., Vanderford, B.J., Kolstad, C., Zeigler-Holady, J.C. and Dickenson, E.R., 2014. Treatment of poly-and perfluoroalkyl substances in US full-scale water treatment systems. Water Research, 51, 246-255. [http://dx.doi.org/10.1016/j.watres.2013.10.067  doi: 10.1016/j.watres.2013.10.067 ]</ref>. However, granular activated carbon has a relatively low capacity for PFASs particularly when shorter-chain compounds are present. Sorption capacity improvement tests have been conducted on various forms of granular and powdered activated carbon, ion exchange, and other sorbent materials and mixtures of clay, powdered activated carbon, and other sorbents<ref>Du, Z., Deng, S., Bei, Y., Huang, Q., Wang, B., Huang, J. and Yu, G., 2014. Adsorption behavior and mechanism of perfluorinated compounds on various adsorbents-A review. Journal of Hazardous Materials, 274, 443-454. [http://dx.doi.org/10.1016/j.jhazmat.2014.04.038 doi:10.1016/j.jhazmat.2014.04.038]</ref>. 

Other methods for ex situ PFAS removal include high-pressure membrane treatment using nanofiltration or reverse osmosis. Membrane technologies at full-scale municipal water treatment facilities have effectively removed PFASs<ref name= "Appleman2014"/>. For typical environmental remediation applications, however, membrane treatment has a higher cost than activated carbon and effectiveness can be impaired by other groundwater contaminants<ref>Department of the Navy (DON). 2015. Interim perfluorinated compounds (PFCs) guidance/frequently asked questions. [[Media:Dept_of_Navy-_2015-Interim_Perfluorinated_Compounds_Frequently_asked_questions.pdf|FAQs]]</ref>. Neutral PFASs, such as the perfluoroalkyl sulfonamides, may not be sufficiently removed<ref>Steinle-Darling, E. and Reinhard, M., 2008. Nanofiltration for trace organic contaminant removal: structure, solution, and membrane fouling effects on the rejection of perfluorochemicals. Environmental Science & Technology, 42 (14), 5292–5297. [http://dx.doi.org/10.1021/es703207s doi: 10.1021/es703207s]</ref>.

==PFAS Treatment Research==
PFAS treatment research includes the following topics:

*'''PFAS Sequestration''': Sorbents are being investigated with the long-term goal of using them in an in situ barrier as a low-cost, long-term treatment solution, combined with a method for periodically regenerating or renewing the emplaced sorbent material and treating waste streams on site using ex-situ chemical oxidation ([https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2423 ESTCP project 2423]<ref>Crimi, M. 2014. In situ treatment train for remediation of perfluoroalkyl contaminated groundwater: In situ chemical oxidation of sorbed contaminants (ISCO-SC), ER-2423. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2423 ER-2423]</ref>). SERDP/ESTCP has also funded research ([https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2425/ER-2425/(language)/eng-US ESTCP project ER-2425]) to test in situ injection of chemical coagulants (e.g., polyaluminum chloride, cationic polymers) to aid with sorption<ref>Simcik, M. (2014). Development of a novel approach for in situ remediation of PFC contaminated groundwater systems, ER-2425. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2425/ER-2425 ER-2425]</ref>.

*'''Proof-of-Concept for Biological Treatment''': Fungi have been used successfully to degrade PFASs under laboratory conditions<ref name= "Tseng2014"/><ref>Qingguo, J. H., 2013. Remediation of perfluoroalkyl contaminated aquifers using an In-situ two-layer barrier: laboratory batch and column study. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2127 ER-2127]</ref>, but are more difficult to maintain in situ. New work ([https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2422/ER-2422/(language)/eng-US ESTCP project ER-2422]) is focused on the viability of packaging the PFAS-degrading enzymes from wood-rotting fungi into “vaults” (naturally-occurring particles found in a wide variety of microorganisms) and using bioaugmentation for in situ degradation<ref>Mahendra, S., 2014. Bioaugmentation with vaults: novel in situ remediation strategy for transformation of perfluoroalkyl compounds, SERDP, ER-2422. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2422/ER-2422 ER-2422]</ref><ref name= "Merino2016"> Merino, N., Qu, Y., Deeb, R.A., Hawley, E.L., Hoffman, M.R and Mahendra, S., 2016. Degradation and removal methods for perfluoroalkyl and polyfluoroalkyl substances (PFASs) in water. Environmental Engineering Science, 33(9), 615-649. [http://dx.doi.org/10.1089/ees.2016.0233 doi:10.1089/ees.2016.0233]</ref>. 

*'''Advanced Oxidation Processes''': Advanced oxidation processes for PFAS include electrochemical oxidation, photolysis, and photocatalysis<ref name= "Merino2016"/>. Electrocatalytic and catalytic approaches using Ti/RuO<sub>2</sub> and other mixed metal oxide anodes have been used to oxidize PFAS in the laboratory under a range of conditions ([https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2424/ER-2424/(language)/eng-US ESTCP project 2424]<ref>Schaefer, C., 2014. Investigating electrocatalytic and catalytic approaches for in situ treatment of perfluoroalkyl contaminants in groundwater, ER-2424. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2424/ER-2424 ER-2424]</ref>).

*'''In Situ Chemical Reduction''': Methods being investigated include the use of zero-valent metals/bimetals (Pd/Fe, Mg, Pd/Mg) with clay interlayers and co-solvent assisted Vitamin B12 defluorination. One ongoing project ([https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2426/ER-2426/(language)/eng-US SERDP project ER-2426]) focuses on PFOS, which is recalcitrant to many oxidation processes<ref>Lee, L., 2014. Quantification of in situ chemical reductive defluorination (ISCRD) of perfluoroalkyl acids in groundwater impacted by AFFFs, ER-2426. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2426/ER-2426 ER-2426]</ref>. Reductive technologies could be used as a first step in remediating PFOS and other PFASs.  

==Summary==
PFASs are present in the environment and pose several challenges. Perfluoroalkyl substances are highly stable and can biomagnify in wildlife. Health-based advisory levels are low, i.e., ng/L concentrations in groundwater and drinking water. As awareness of PFAS grows and regulatory criteria evolve, site managers are conducting site investigation, improving analytical techniques, and designing and operating remediation systems. SERDP/ESTCP-funded research aims to demonstrate effective treatment technologies for PFAS and improve technology cost-effectiveness.

==References==

<references/>

==See Also==
'''Relevant Ongoing SERDP/ESTCP Projects:'''

*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2423. In situ treatment train for remediation of perfluoroalkyl contaminated groundwater: In situ chemical oxidation of sorbed contaminants (ISCO-SC). SERDP/ESTCP Project ER-2423]
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2426/ER-2426/(language)/eng-US. Quantification of In Situ Chemical Reductive Defluorination (ISCRD) of perfluoroalkyl acids in groundwater impacted by AFFFs. SERDP/ESTCP Project ER-2426] 
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2422/ER-2422/(language)/eng-US. Bioaugmentation with vaults: Novel In Situ Remediation Strategy for Transformation of Perfluoroalkyl Compounds. SERDP/ESTCP Project ER-2422]
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2424/ER-2424/(language)/eng-US. Investigating Electrocatalytic and Catalytic Approaches for In Situ Treatment of Perfluoroalkyl Contaminants in Groundwater. SERDP/ESTCP project ER-2424]
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2425/ER-2425/(language)/eng-US. Development of a Novel Approach for In Situ Remediation of Pfc Contaminated Groundwater Systems. SERDP/ESTCP project ER-2425]