Difference between revisions of "Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)"

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Environmental releases of perfluoroalkyl and polyfluoroalkyl substances (PFAS) 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. PFAS 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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Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals suspected to cause adverse human and ecological health effects. The acronym “PFAS” encompasses thousands of individual compounds. The two most studied and regulated are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). PFAS, including PFOA and PFOS, have entered the environment from a variety of sources and release scenarios, including releases from manufacturing facilities and areas where aqueous film-forming foam (AFFF), a type of fire-fighting foam, was applied. Many PFAS have unique physical and chemical properties that render them highly stable and resistant to degradation in the environment. They are typically removed from water supplies using granular activated carbon or ion exchange resins, although research is ongoing to develop ''in situ'' treatment technologies as well as more cost-effective ''ex situ'' treatment methods.
  
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
'''Related Article(s):'''
 
'''Related Article(s):'''
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*[[PFAS Ex Situ Water Treatment]]
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*[[PFAS Soil Remediation Technologies]]
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*[[PFAS Sources]]
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*[[PFAS Transport and Fate]]
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*[[PFAS Treatment by Electrical Discharge Plasma]]
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*[[Photoactivated Reductive Defluorination - PFAS Destruction]]
 
*[[Soil & Groundwater Contaminants]]
 
*[[Soil & Groundwater Contaminants]]
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*[[Supercritical Water Oxidation (SCWO)]]
  
  
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'''CONTRIBUTOR(S):''' [[Dr. Rula Deeb]], [[Dr. Jennifer Field]], [[Elisabeth Hawley]], and [[Dr. Christopher Higgins]]
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'''Contributor(s):''' [[Dr. Rula Deeb]], [[Dr. Jennifer Field]], Dr. Lydia Dorrance, [[Elisabeth Hawley]] and [[Dr. Christopher Higgins]]
  
  
 
'''Key Resource(s):'''
 
'''Key Resource(s):'''
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*[[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>
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*[//www.enviro.wiki/images/2/2a/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 Fact Sheet – Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA). EPA 505-F-14-001. [//www.enviro.wiki/images/2/2a/USEPA-2014-Emerging_Contaminants_-_PFOS_and_PFOA_Fact_Sheet.pdf March Fact Sheet]</ref>
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*[https://www.epa.gov/sites/production/files/2017-12/documents/ffrrofactsheet_contaminants_pfos_pfoa_11-20-17_508_0.pdf Technical Fact Sheet: Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA)<ref name="USEPA2017">U.S. Environmental Protection Agency, 2017. Technical Fact Sheet: Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA). EPA 505-F-17-001.</ref>][[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)#cite%20note-USEPA2017-2|<span class="mw-reflink-text">[2]</span>]][[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)#cite%20note-USEPA2017-2|<span class="mw-reflink-text">[2]</span>]][[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)#cite%20note-USEPA2017-2|<span class="mw-reflink-text">[2]</span>]][[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)#cite%20note-USEPA2017-2|<span class="mw-reflink-text">[2]</span>]].
  
 
==Introduction==
 
==Introduction==
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Awareness of PFAS 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 PFAS. SERDP/ESTCP research programs began funding related research in 2011 because they recognized the potential impact of this issue for the Department of Defense.
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PFAS were first developed in the 1940s and have been used by numerous industrial and commercial sectors for products that benefited from PFAS’ unique properties, including thermal and chemical stability, water resistance, stain resistance, and their [[wikipedia: Surfactant |surfactant]] nature. Awareness of PFAS in the environment first emerged in the late 1990s following developments in analytical instrumentation which enhanced detection of ionized substances such as PFAS<ref>Hansen, K.J., L.A. Clemen, M.E. Ellefson and H.O. Johnson, 2001. Compound-Specific, Quantitative Characterization of Organic Fluorochemicals in Biological Matrices. Environmental Science and Technology 35(4):766-770.</ref>. This environmental awareness was generally concurrent to increased scrutiny into the health effects of PFAS<ref>U.S. Environmental Protection Agency, 2018. Risk Management for Per- and Polyfluoroalkyl Substances (PFASs) under TSCA. https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/risk-management-and-polyfluoroalkyl-substances-pfass</ref>. In 2000, the sole U.S. manufacturer of PFOS voluntarily discontinued production<ref>U.S. Environmental Protection Agency, 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>. Shortly thereafter, legal actions were taken against PFAS product manufacturing facilities in the Ohio River Valley in West Virginia<ref>Rich, N., 2016. The lawyer who became DuPont’s worst nightmare. The New York Times Magazine.</ref>. Between 2006 and 2015, in cooperation with the EPA, eight global companies with PFAS-related operations voluntarily phased out the manufacture of PFOA and similarly structured PFAS with longer carbon chains<ref>U.S. Environmental Protection Agency, 2018. Fact Sheet: 2010/2015 PFOA Stewardship Program. https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/fact-sheet-20102015-pfoa-stewardship-program</ref>. In 2011, recognizing the potential impact of PFAS for the Department of Defense due to the military’s ubiquitous use of PFAS-containing AFFF, SERDP/ESTCP research programs began funding PFAS-related research, and the U.S. Air Force began conducting initial site investigations at former fire-fighting training areas<ref>SERDP/ESTCP website on Per- and Polyfluorinated Substances (PFASs). https://www.serdp-estcp.org/Featured-Initiatives/Per-and-Polyfluoroalkyl-Substances-PFASs</ref>. The U.S. Environmental Protection Agency (EPA) issued provisional drinking water health advisories for PFOA and PFOS in 2009 and replaced these with more stringent health advisories in 2016<ref name="USEPA2016">U.S. Environmental Protection Agency, 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, regulating agencies in several states have issued screening levels, notification levels, and health-based guidelines for PFOS, PFOA and other PFAS. Several states have undertaken statewide sampling programs of drinking water systems and groundwater resources in the vicinity of potential source areas including manufacturing facilities, military fire-training facilities, airports, refineries, and landfills<ref>California State Water Resources Control Board, 2019. PFAS Phased Investigation Approach. https://www.waterboards.ca.gov/pfas/docs/7_investigation_plan.pdf</ref><ref>Michigan, 2019. PFAS response. Taking Action, Protecting Michigan. Michigan PFAS Action Response Team (MPART).</ref>.
  
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==Physical and Chemical Properties==
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==Nomenclature==
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[[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).]]
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[[File:PFASupdate2019Fig1.png | thumbnail | left | 700 px |Figure 1. PFAS families of compounds<ref name="OECD2015">Organisation for Economic Cooperation and Development, 2015. Working Towards a Global Emission Inventory of PFASs: Focus on PFCAs – Status Quo and the Way Forward. Paris: Environment, Health and Safety, Environmental Directorate, OECD/UNEP Global PFC Group.</ref>]]
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Although the environmental remediation industry initially used the term “perfluorinated compounds” (or PFCs), the more specific terminology of PFAS 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>. PFAS 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).  
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[[File:Deeb-Article 1-Figure 1.JPG|thumbnail|right|400 px|Figure 2. a) Structure of a perfluoroalkyl substance, PFOS, compared with b) the structure of a polyfluoroalkyl substance, 6:2 fluorotelomer sulfonate (6:2 FTSA).]]
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[[File:PFAS_naming_red.mp4 | thumb | right | 400px | Figure 3. PFAS naming conventions explained.]]
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There are over 3,000 PFAS currently on the global market. A summary of families of compounds that are included in the umbrella terminology “PFAS” is provided in Figure 1<ref name="OECD2015" />. Perfluoroalkyl compounds have a non-polar hydrophobic carbon (alkyl) chain structure that is fully saturated with fluorine atoms (i.e., they are perfluoroalkyl substances) attached to a hydrophilic polar functional group. Polyfluoroalkyl compounds have a similar structure but have at least one carbon that is bound to hydrogen rather than fluorine (Figure 2). Carbon chains may be linear or branched, leading to a variety of isomers. The term PFAS also includes fluoropolymers that may consist of thousands of shorter-chain units bonded together<ref name="ITRC2018">Interstate Technology and Regulatory Council, 2018. Naming Conventions and Physical and Chemical Properties of Per- and Polyfluoroalkyl Substances (PFAS). https://pfas-1.itrcweb.org/wp-content/uploads/2018/03/pfas_fact_sheet_naming_conventions__3_16_18.pdf</ref>.
  
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The most studied PFAS 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 PFAS creates extremely high chemical and thermal stabilities. Relevant properties of PFOS and PFOA are summarized below (Table 1<ref name= "USEPA2014"/>).  
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One of the most studied and regulated families of perfluoroalkyl compounds are the perfluoroalkyl acids (PFAAs), which include perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs).  PFOA, a perfluoroalkyl carboxylic acid, and PFOS, a perfluoroalkyl sulfonic acid, are both PFAAs with eight carbons. Other PFCAs with the number of carbons ranging from nine to four include perfluorononanoic acid (PFNA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), and perfluorobutanoic acid (PFBA).  PFAAs are sometimes differentiated as “long-chain” or “short-chain.” The term “long-chain” refers to PFCAs with eight or more carbons and PFSAs with six or more carbons. The term “short-chain” refers to PFCAs with seven or fewer carbons and PFSAs with five or fewer carbons<ref name="ITRC2018" />.The PFAS naming conventions are explained in more detail in the video shown in Figure 3.
  
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==Physical and Chemical Properties==
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{| class="wikitable" style="float:right; margin-left:10px;"
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{| class="wikitable"
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|+Table 1. Physical and Chemical Properties of PFOS and PFOA.<ref name="USEPA2014" /><ref name="USEPA2017" /><ref name="ITRC2018b">Interstate Technology Regulatory Council, 2018. PFAS Fact Sheets: Environmental Fate and Transport, Table 3-1.  https://pfas-1.itrcweb.org/wp-content/uploads/2018/05/ITRCPFASFactSheetFTPartitionTable3-1April18.xlsx</ref><ref name="ATSDR2018">Agency for Toxic Substances and Disease Registry, 2018. ToxGuide<sup><small>TM</small></sup> for Perfluoroalkyls. https://www.atsdr.cdc.gov/toxguides/toxguide-200.pdf </ref>
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|+ Table 1. Physical and Chemical Properties of PFOS and PFOA<ref name= "USEPA2014"/>.
 
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! Property
 
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! PFOS (Potassium Salt)
 
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! PFOA (Free Acid<sup>''1''</sup>)
 
 
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|-
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| Chemical Abstracts Service Number || 2795-35-3 || 335-67-1
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!Property
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!PFOS (Free Acid)
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!PFOA (Free Acid)
 
|-
 
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| Physical State (at 25&deg; C and 1 atmosphere pressure) || White powder || White powder/waxy white solid
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|Chemical Abstracts Service Number||1763-23-1||335-67-1
 
|-
 
|-
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| Molecular weight (g/mol) || 538 || 414
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|Physical State (at 25&deg; C and 1 atmosphere pressure)||White powder||White powder/waxy white solid
 
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| Water solubility at 25&deg; C (mg/L) || 550 to 570<sup>''2''</sup>, 370<sup>''3''</sup>, 25<sup>''4''</sup> || 9,500<sup>''2''</sup>
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|Molecular weight (g/mol)||500||414
 
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|-
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| Melting point (&deg;C) ||>400 || 45 to 54
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|Water solubility at 25&deg; C (mg/L)||570<sup>''a''</sup>||9,500<sup>''a''</sup>
 
|-
 
|-
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| Boiling point (&deg;C) || Not measurable || 188 to 192
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|Melting point (&deg;C)||No data||45 to 54
 
|-
 
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| Vapor pressure at 20&deg; C (mm Hg) || 2.48x10<sup>-6</sup> || 0.017<sup>''5''</sup>
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|Boiling point (&deg;C)||258 to 260||188 to 192
 
|-
 
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| Octanol-water partition coefficient (log ''K<sub>ow</sub>'') || Not measurable || Not measurable
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|Vapor pressure at 20&deg; C (mm Hg)||0.002||0.525 to 10
 
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|-
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| Organic-carbon partition coefficient (log ''K<sub>oc</sub>'') || 2.57<sup>''6''</sup> || 2.06
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|Organic-carbon partition coefficient (log ''K<sub>oc</sub>'')||2.4 to 3.7||1.89 to 2.63
 
|-
 
|-
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| Henry’s Law constant (atm-m<sup>3</sup>/mol) || 3.05x10<sup>-9</sup> || Not measurable
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|Henry’s Law constant (atm-m<sup>3</sup>/mol)||Not measurable||3.57x10<sup>-6</sup>
 
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| Half-life || Atmospheric: 114 days</br>Water: >41 years (at 25&deg; C) || Atmospheric: 90 days<sup>''7''</sup></br>Water: >92 years (at 25&deg; C)
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|Half-life||Atmospheric: 114 days<br>Water: >41 years (at 25&deg; C)<br>Human: 3.1 to 7.4 years||Atmospheric: 90 days<sup>''b''</sup><br>Water: >92 years (at 25&deg; C)<br>Human: 2.1 to 8.5 years
 
|-
 
|-
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| colspan="3" | Abbreviations: g/mol = grams per mole; mg/L = milligrams per liter; &deg;C = degrees Celsius; mm Hg = millimeters of mercury; atm-m<sup>3</sup>/mol = atmosphere-cubic meters per mole.
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| colspan="3" style="background:white;" |Abbreviations: g/mol = grams per mole; mg/L = milligrams per liter; &deg;C = degrees Celsius; mm Hg = millimeters of mercury; atm-m<sup>3</sup>/mol = atmosphere-cubic meters per mole
 
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|-
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| colspan="3" | Notes: <sup>''1''</sup> The salt form of PFOA is more likely to be environmentally and toxicological relevant; however, its properties are not available.  <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.
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| colspan="3" style="background:white;" |Notes: <sup>''a''</sup> Solubility in purified water. <sup>''b''</sup> The atmospheric half-life value for PFOA was extrapolated from available data measured over short study periods.
 
|}
 
|}
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The combination of the polar and non-polar structure makes PFAAs “amphiphilic,” associating with both water and oils, while the strength of their [[wikipedia: Carbon-fluorine bond |carbon-fluorine bonds]] lends them extremely high chemical and thermal stabilities. In most groundwater and surface water environments, PFAAs are found as the water-soluble anionic (i.e. deprotonated, negatively charged) form. Other groups of PFAS can be cationic (positively charged) or zwitterionic (possessing both a positive and negative charge) under typical environmental conditions. In general, documented physical properties of PFAS are scarce, and much that is available for PFAAs is related to the acid forms of the compounds, which are not typically found in the environment<ref name="ITRC2018" />. The surfactant properties of PFAAs complicate the prediction of their physiochemical properties, such as vapor pressure and partitioning coefficients. Some relevant properties of PFOS and PFOA are summarized in Table 1. A summary of the general characteristics of PFAS has been compiled in Table 6-2 of the [https://pfas-1.itrcweb.org/wp-content/uploads/2018/03/pfas_fact_sheet_naming_conventions__3_16_18.pdf ITRC fact sheet on PFAS naming conventions and physical and chemical properties]<ref name="ITRC2018" />.
  
 
==Environmental Concern==
 
==Environmental Concern==
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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"/>.
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Environmental concern surrounding PFAS stems from their widespread detection, high degree of environmental stability and mobility, and suspected toxicological effects on humans and the environment. Perfluorinated compounds, including PFAAs, are very stable and do not biodegrade. As a result, these compounds are found throughout the global environment. Trace amounts of perfluorinated compounds 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 some 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, and humans who consume them, can be particularly susceptible to any deleterious health effects posed by PFAS<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" />. Recent fish and wildlife consumption advisories have been issued at certain locations in the United States associated with PFAS contamination<ref>Minnesota Department of Health, 2018. Media FAQ: Fish Consumption Advisory, PFOS and Lake Elmo Fish 2018. https://www.co.washington.mn.us/DocumentCenter/View/20895/FAQ-2018-Fish-Consumption-Advisory-NR </ref><ref>State of Michigan, PFAS Response, Taking Action, Protecting Michigan, 2019. https://www.michigan.gov/pfasresponse/0,9038,7-365-86512_88981_88982---,00.html </ref>.
  
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PFAS 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.
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Like other aspects of PFAS research, information on the toxicological effects of PFAS on humans is still emerging. PFOA and PFOS have half-lives of 2.1-8.5 years and 3.1-7.4 years, respectively, in humans<ref name="ATSDR2018" />. PFAS typically accumulate in the liver, proteins, and the blood stream<ref name="USEPA2017" />. Toxicological and epidemiological studies of PFOA, PFOS and other PFAAs indicate potential association with a constellation of ailments including decreased fertility, increased cholesterol, suppression of response to vaccines, and certain cancers<ref name="ATSDR2018" /><ref>C8 Science Panel, 2012. C8 Probable Link Reports. http://www.c8sciencepanel.org/prob_link.html </ref>. Both PFOA and PFOS are suspected carcinogens, but their carcinogenicity remains to be classified by the U.S. EPA<ref name="USEPA2017" />. 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. [//www.enviro.wiki/images/f/fd/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 oral reference doses of 20 ng/kg-day for both PFOA and PFOS (based on non-cancer hazard)<ref name="USEPA2017" />. Drinking water ingestion, fish consumption, dermal contact with water, and (accidental) ingestion of or contact with contaminated soil are the exposure pathways of concern with respect to human health.
  
 
==Uses and Potential Sources to the Environment==
 
==Uses and Potential Sources to the Environment==
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Due to their unique properties, many PFAS 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"/>. PFAS 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 PFAS: 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 (PFAS) 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>.  
+
Due to their unique properties, including surfactant qualities, heat and stain resistance, and [[wikipedia: Amphiphile |amphiphilic]] nature, PFAS are used widely by a number of industries, including carpet, textile and leather production, chromium plating, photography, [[wikipedia: Photolithography |photolithography]], paper products, semi-conductor manufacturing, coating additives, and cleaning products<ref name="ITRC2017">Interstate Technology and Regulatory Council, 2017. History and Use of Per- and Polyfluoroalkyl Substances (PFAS). https://pfas-1.itrcweb.org/wp-content/uploads/2017/11/pfas_fact_sheet_history_and_use__11_13_17.pdf </ref><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>. Sources to the environment include primary manufacturing facilities, where PFAS is produced, and secondary manufacturing facilities, where PFAS is incorporated into products. PFAS are found in a variety of consumer products including food paper and packaging, furnishings, waterproof clothing, and cosmetics<ref name="BirnbaumGrandjean2015">Birnbaum, L.S. and Grandjean, P., 2015. Alternatives to PFAS: 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 PFAS 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 (PFAS) 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 PFAS 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 (PFAS). Presented on July 6. [[Media:Conder-2008-GRACast_Frequently_asked_questions_on_PFAS.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>.
+
An additional widely documented source of PFAS is AFFF. AFFF is as a Class B firefighting foam used to combat flammable liquid fires. AFFF was released in large quantities at firefighting training areas as part of routine handling, fire-suppression training and equipment testing, and during fire emergency responses. While all AFFF contains PFAS<ref>Interstate Technology and Regulatory Council, 2018. Aqueous Film-Forming Foam (AFFF). https://pfas-1.itrcweb.org/wp-content/uploads/2019/03/pfas-fact-sheet-afff-10-3-18.pdf </ref>, the types and concentrations of PFAS in AFFF vary among manufacturers and manufacturing time periods. 3M AFFF products were made using an [[wikipedia: Electrochemical fluorination |electrochemical fluorination]] process that produced a high percentage of PFAS as PFOS, while other formulations were made using a [[wikipedia: Teolmerization |telomerization]] process and contain a different suite of PFAS.  
  
 
==Regulation==
 
==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 PFAS 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>.
+
The U.S. EPA recently developed Drinking Water Health Advisory levels for PFOA and PFOS, replacing previously published provisional values<ref name="USEPA2016" />. However, no Federal enforceable drinking water standards have been set. Recent years have seen increased regulatory activity at the state level, with around 20 states having guidance or advisory levels for one or more PFAS compounds in various environmental media (drinking water, groundwater, etc.). New Jersey is the first state to have promulgated an enforceable maximum concentration level (MCL) for a PFAS by setting an MCL for PFNA in 2018. Several other states, particularly in the eastern United States, are moving towards setting MCLs for various PFAS. Regulatory levels set or proposed by states vary but the majority are equivalent to or lower than the Federal Health Advisory level of 70 parts per trillion (ppt) combined concentration of PFOA and PFOS. The regulatory landscape for PFAS is developing rapidly. A regularly updated repository of [https://pfas-1.itrcweb.org/fact-sheets/ regulatory levels] is maintained by the ITRC (Figure 4). [[File:ITRCfactSheetPFAS.png |thumb|left|400px| link=https://pfas-1.itrcweb.org/fact-sheets/ | [https://pfas-1.itrcweb.org/fact-sheets/ Figure 4. ITRC PFAS Fact Sheets: 1. Naming Conventions and Physical and Chemical Properties, 2. Regulations, Guidance, and Advisories, 3. History and Use, 4. Environmental Fate and Transport, 5. Site Characterization Tools, Sampling Techniques, and Laboratory Analytical Methods, and 6. Remediation Technologies and Methods.]]]
  
−
Other regulatory actions have restricted the use and production of PFAS. 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.  
+
Other regulatory actions have restricted the use and production of PFAS. PFOS was added to list of chemicals under the [[wikipedia: Stockholm Convention on Persistent Organic Pollutants |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<ref>Darwin, R.L., 2011. Estimated Inventory of PFOS-based Aqueous Film Forming Foam (AFFF). July. https://www.informea.org/sites/default/files/imported-documents/UNEP-POPS-POPRC13FU-SUBM-PFOA-FFFC-3-20180112.En.pdf </ref><ref>Department of Defense, 2018. Alternatives to Aqueous Film Forming Foam Report to Congress, June. https://www.denix.osd.mil/derp/home/documents/alternatives-to-aqueous-film-forming-foam-report-to-congress/ </ref>.
  
−
{| class="wikitable"
+
==Litigation==
−
|-
+
There have been many lawsuits filed with PFAS-related claims; some resulting in settlements in the hundreds of millions of dollars. In 2017 DuPont and Chemours paid nearly $700 million to settle 3,550 individual lawsuits claiming personal injury as a result of PFOA releases from DuPont’s former Washington Works manufacturing facility in Parkersburg, West Virginia. This settlement was reached after three of the lawsuits went to trial resulting in nearly $20 million in jury awards to the plaintiffs<ref>Reisch, M.S. “DuPont, Chemours settle PFOA suits” Chem. & Eng. News, Feb. 20, 2017. https://cen.acs.org/articles/95/i8/DuPont-Chemours-settle-PFOA-suits.html </ref>. In 2018, 3M agreed to pay $850 million to settle a $5 billion natural resource damages claim related to PFAS impacts brought by Minnesota’s Attorney General<ref>Bellon, T. 3M, Minnesota settle water pollution claims for $850 million, Reuters, Feb. 20, 2018. https://www.reuters.com/article/us-3m-pollution-minnesota/3m-minnesota-settle-water-pollution-claims-for-850-million-idUSKCN1G42UW </ref>. In early 2019, numerous product liability lawsuits against former manufacturers of PFOS and PFOA and manufacturers of AFFF were consolidated into a multi-district litigation (MDL) pending before the U.S District Court of South Carolina<ref>United States District Court of South Carolina. Aqueous Film-Forming Foams (AFFF) Products Liability Litigation MDL No. 2873. https://www.scd.uscourts.gov/mdl-2873/ </ref>. Numerous additional PFAS-related lawsuits have been brought under common law tort, personal injury, product liability and natural resource protection laws across the United States. The proposed designation of PFAS as a hazardous substance under [[wikipedia: Superfund |CERCLA]]<ref>Congressional Research Service, 2019. Regulating Drinking Water Contaminants: EPA PFAS Actions. August. https://fas.org/sgp/crs/misc/IF11219.pdf </ref> may have additional legal implications.
−
!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 PFAS 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 PFAS 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==
 
==Sampling and Analytical Methods==
−
Because PFAS are present in several common consumer items, care should be taken during sampling to eliminate contact with other potential sources of PFAS. 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 PFAS for the air-water interface and the wettability of glass, sample bottles are typically polypropylene or high-density polyethylene.
+
Because of the presence of PFAS in many common consumer items and sampling materials, and the low reporting levels needed to compare to current regulatory guidelines, sampling for PFAS requires extra care to avoid cross contamination from other potential sources of PFAS. Most standard operating procedures and work plans advise avoiding the use of fluoropolymer-based (e.g., Teflon) components and recommend additional precautions related to sample containers, sampler clothing and handling of certain every-day items.  
−
 
 
−
Most commercial laboratories use a modified version of U.S. EPA Method 537 for the analysis of PFAS 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 PFAS (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 PFAS (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 (PFAS): 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>.
+
Commercial laboratories analyze PFAS in drinking water samples using the EPA-approved method 537.1, which consists of [[wikipedia: Solid phase extraction |solid phase extraction]] and [[wikipedia: Liquid chromatography-mass spectrometry |liquid chromatography with tandem mass spectrometry]]<ref>U.S. Environmental Protection Agency, 2019. Method 537.1 Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). August. https://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryId=343042&Lab=NERL </ref>. Samples collected from any environmental media other than drinking water require a modified version of 537.1 to quantify approximately 24 individual PFAS compounds. An EPA method for some of these other media, Method 8327, was released for public comment in summer 2019<ref>U.S. Environmental Protection Agency, 2019. SW-486 Update VII Announcements, Phase II – PFAS 8372 and 3512, July. https://www.epa.gov/hw-sw846/sw-846-update-vii-announcements </ref>. Some commercial laboratories can extend the target analyte list to include up to 40 compounds. Some commercial laboratories also offer an analytical method known as the [[Wikipedia: TOP Assay | Total Oxidizable Precursor (TOP) Assay]], which provides a bulk measurement of PFAS mass in a sample, including that of oxidizable precursors<ref>Houtz, E.F., and Sedlak, D.L., 2012. Oxidative conversion as a means of detecting precursors to perfluoroalkyl acids in urban runoff. Environmental Science & Technology, 46(17), 9342-9349. doi/10.1021/es302274g </ref><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. doi: 10.1021/es4018877 </ref>. Other approaches to quantify the total amount of organic fluorine in water samples include [[wikipedia: Particle-induced gamma emission |particle induced gamma-ray emission]] (PIGE) and absorbable organic fluorine (AOF)<ref name="BirnbaumGrandjean2015" />.
  
−
The cost-effectiveness of high-resolution site characterization methods for PFAS 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 PFAS 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==
 
==Fate and Transport==
−
The following summarize some key concepts for PFAS fate and transport:
+
The processes of [[wikipedia: Sorption |sorption]] and biotransformation as well as the presence of co-contaminants can affect the fate and transport of PFAS. It has been observed that PFAAs exhibit affinity for solid-phase organic carbon to varying degrees depending in part on chain length and structure, with long-chain compounds exhibiting a stronger affinity than short-chain and PFSAs exhibiting a stronger affinity than PFCAs for a given chain length<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>. Interactions with mineral phases, particularly ferric oxide materials, may also be important under certain conditions<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" />. PFAAs do not readily degrade in the environment. However, polyfluorinated forms may biotically or abiotically degrade to other intermediate forms and/or so-called “terminal,” recalcitrant PFAA forms, including PFOA and PFOS<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><ref>Ellis, D.A., Martin, J.W., De Silva, A.O., Marbury, S.A., Hurley, M.D., Sulbaek Andersen, M.P., and T.J. Wallington, 2004. Degradation of fluorotelomer alcohols: a likely atmospheric source of perfluoronated carboxylic acids. Environmental Science & Technology 38(12), 3316-3321. doi/10.1021/es049860w </ref>. As a result, these degradable PFAS are sometimes referred as PFAA “precursors.” Remediation of co-contaminants, particularly using techniques involving oxidation, can enhance the degradation of precursors. Interactions between PFAS 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. [//www.enviro.wiki/images/d/d8/Guelfo-2013-Subsuface_fate_and_transport_of_Poly-and_perfluoroalkyl_substances.pdf Thesis]</ref>
−
 
 
−
*'''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 PFAS. 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 (PFAS) 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 PFAS 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 PFAS<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 PFAS 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 PFAS 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 PFAS 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 PFAS 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 PFAS<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 PFAS, 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>.
+
==Remediation Technologies==
−
 
+
Due to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures, soil and groundwater remediation is challenging and costly. Research is still ongoing to develop effective remedial strategies. Treatment options for soil include 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. 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 [[wikipedia: Activated carbon |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 PFAS particularly when shorter-chain compounds are present. Sorption capacity improvement tests have been conducted on various forms of granular and powdered activated carbon, [[wikipedia: Ion-exchange resin |ion exchange resins]], and other sorbent materials as well as 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 [[wikipedia: Nanofiltration |nanofiltration]] or [[wikipedia: Reverse osmosis |reverse osmosis]]<ref name="Appleman2014" /><ref>Department of the Navy (DON). 2015. Interim perfluorinated compounds (PFCs) guidance/frequently asked questions. [//www.enviro.wiki/images/b/b1/Dept_of_Navy-_2015-Interim_Perfluorinated_Compounds_Frequently_asked_questions.pdf FAQs]</ref><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>. Research into other PFAS treatment technologies, including ''in situ'' barriers (sequestration), biological treatment<ref>Huang, Shan and Jaffe, Peter R., 2019. Defluorination of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) by ''Acidimicrobium'' sp. Strain A6. Environmental Science and Technology, 53, pp 11410-11419.  DOI:10.1021/acs.est.9b04047 https://pubs.acs.org/doi/full/10.1021/acs.est.9b04047 </ref>, [[wikipedia: Advanced oxidation process |advanced oxidation processes]] and [[Chemical Reduction (In Situ - ISCR) |''in situ'' chemical reduction]] is ongoing.  
−
*'''Proof-of-Concept for Biological Treatment''': Fungi have been used successfully to degrade PFAS 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 (PFAS) 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 PFAS.
 
  
 
==Summary==
 
==Summary==
−
PFAS 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.
+
PFAS are ubiquitous in a variety of industrial and commercial products, have been detected in many environmental media, pose potential risks to human and environmental health, and present challenges with respect to remediation. They are highly stable and mobile in the environment, may bioaccumulate and biomagnify in wildlife, and are the subject of litigation and regulatory actions at the local, state and Federal level. Health-based drinking water advisory levels are low, i.e., ng/L concentrations. As awareness of PFAS grows and regulatory criteria progress, site managers are conducting site investigations, improving analytical techniques, and designing and operating remediation systems. Current research, including that funded by SERDP/ESTCP, aims to demonstrate effective treatment technologies for PFAS and improve technology cost-effectiveness.
  
 
==References==
 
==References==
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+
<references />
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<references/>
 
  
 
==See Also==
 
==See Also==
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'''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-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-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-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-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]
 
*[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]
 +
*[https://serdp-estcp.mil/projects/details/d8fdde05-10b6-43d4-a4d3-2a1a60329392/pfas-podcast-series-serdp-and-estcp-research-and-demonstrations PFAS Podcast Series: SERDP and ESTCP Research and Demonstrations. SERDP/ESTCP project ER23-7692]

Latest revision as of 19:23, 31 October 2024

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals suspected to cause adverse human and ecological health effects. The acronym “PFAS” encompasses thousands of individual compounds. The two most studied and regulated are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). PFAS, including PFOA and PFOS, have entered the environment from a variety of sources and release scenarios, including releases from manufacturing facilities and areas where aqueous film-forming foam (AFFF), a type of fire-fighting foam, was applied. Many PFAS have unique physical and chemical properties that render them highly stable and resistant to degradation in the environment. They are typically removed from water supplies using granular activated carbon or ion exchange resins, although research is ongoing to develop in situ treatment technologies as well as more cost-effective ex situ treatment methods.

Related Article(s):


Contributor(s): Dr. Rula Deeb, Dr. Jennifer Field, Dr. Lydia Dorrance, Elisabeth Hawley and Dr. Christopher Higgins


Key Resource(s):

Introduction

PFAS were first developed in the 1940s and have been used by numerous industrial and commercial sectors for products that benefited from PFAS’ unique properties, including thermal and chemical stability, water resistance, stain resistance, and their surfactant nature. Awareness of PFAS in the environment first emerged in the late 1990s following developments in analytical instrumentation which enhanced detection of ionized substances such as PFAS[3]. This environmental awareness was generally concurrent to increased scrutiny into the health effects of PFAS[4]. In 2000, the sole U.S. manufacturer of PFOS voluntarily discontinued production[5]. Shortly thereafter, legal actions were taken against PFAS product manufacturing facilities in the Ohio River Valley in West Virginia[6]. Between 2006 and 2015, in cooperation with the EPA, eight global companies with PFAS-related operations voluntarily phased out the manufacture of PFOA and similarly structured PFAS with longer carbon chains[7]. In 2011, recognizing the potential impact of PFAS for the Department of Defense due to the military’s ubiquitous use of PFAS-containing AFFF, SERDP/ESTCP research programs began funding PFAS-related research, and the U.S. Air Force began conducting initial site investigations at former fire-fighting training areas[8]. The U.S. Environmental Protection Agency (EPA) issued provisional drinking water health advisories for PFOA and PFOS in 2009 and replaced these with more stringent health advisories in 2016[9]. Over the past five years, regulating agencies in several states have issued screening levels, notification levels, and health-based guidelines for PFOS, PFOA and other PFAS. Several states have undertaken statewide sampling programs of drinking water systems and groundwater resources in the vicinity of potential source areas including manufacturing facilities, military fire-training facilities, airports, refineries, and landfills[10][11].

Nomenclature

Figure 1. PFAS families of compounds[12]
Figure 2. a) Structure of a perfluoroalkyl substance, PFOS, compared with b) the structure of a polyfluoroalkyl substance, 6:2 fluorotelomer sulfonate (6:2 FTSA).
Figure 3. PFAS naming conventions explained.

There are over 3,000 PFAS currently on the global market. A summary of families of compounds that are included in the umbrella terminology “PFAS” is provided in Figure 1[12]. Perfluoroalkyl compounds have a non-polar hydrophobic carbon (alkyl) chain structure that is fully saturated with fluorine atoms (i.e., they are perfluoroalkyl substances) attached to a hydrophilic polar functional group. Polyfluoroalkyl compounds have a similar structure but have at least one carbon that is bound to hydrogen rather than fluorine (Figure 2). Carbon chains may be linear or branched, leading to a variety of isomers. The term PFAS also includes fluoropolymers that may consist of thousands of shorter-chain units bonded together[13].

One of the most studied and regulated families of perfluoroalkyl compounds are the perfluoroalkyl acids (PFAAs), which include perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs). PFOA, a perfluoroalkyl carboxylic acid, and PFOS, a perfluoroalkyl sulfonic acid, are both PFAAs with eight carbons. Other PFCAs with the number of carbons ranging from nine to four include perfluorononanoic acid (PFNA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), and perfluorobutanoic acid (PFBA). PFAAs are sometimes differentiated as “long-chain” or “short-chain.” The term “long-chain” refers to PFCAs with eight or more carbons and PFSAs with six or more carbons. The term “short-chain” refers to PFCAs with seven or fewer carbons and PFSAs with five or fewer carbons[13].The PFAS naming conventions are explained in more detail in the video shown in Figure 3.

Physical and Chemical Properties

Table 1. Physical and Chemical Properties of PFOS and PFOA.[1][2][14][15]
Property PFOS (Free Acid) PFOA (Free Acid)
Chemical Abstracts Service Number 1763-23-1 335-67-1
Physical State (at 25° C and 1 atmosphere pressure) White powder White powder/waxy white solid
Molecular weight (g/mol) 500 414
Water solubility at 25° C (mg/L) 570a 9,500a
Melting point (°C) No data 45 to 54
Boiling point (°C) 258 to 260 188 to 192
Vapor pressure at 20° C (mm Hg) 0.002 0.525 to 10
Organic-carbon partition coefficient (log Koc) 2.4 to 3.7 1.89 to 2.63
Henry’s Law constant (atm-m3/mol) Not measurable 3.57x10-6
Half-life Atmospheric: 114 days
Water: >41 years (at 25° C)
Human: 3.1 to 7.4 years		 Atmospheric: 90 daysb
Water: >92 years (at 25° C)
Human: 2.1 to 8.5 years
Abbreviations: g/mol = grams per mole; mg/L = milligrams per liter; °C = degrees Celsius; mm Hg = millimeters of mercury; atm-m3/mol = atmosphere-cubic meters per mole
Notes: a Solubility in purified water. b The atmospheric half-life value for PFOA was extrapolated from available data measured over short study periods.

The combination of the polar and non-polar structure makes PFAAs “amphiphilic,” associating with both water and oils, while the strength of their carbon-fluorine bonds lends them extremely high chemical and thermal stabilities. In most groundwater and surface water environments, PFAAs are found as the water-soluble anionic (i.e. deprotonated, negatively charged) form. Other groups of PFAS can be cationic (positively charged) or zwitterionic (possessing both a positive and negative charge) under typical environmental conditions. In general, documented physical properties of PFAS are scarce, and much that is available for PFAAs is related to the acid forms of the compounds, which are not typically found in the environment[13]. The surfactant properties of PFAAs complicate the prediction of their physiochemical properties, such as vapor pressure and partitioning coefficients. Some relevant properties of PFOS and PFOA are summarized in Table 1. A summary of the general characteristics of PFAS has been compiled in Table 6-2 of the ITRC fact sheet on PFAS naming conventions and physical and chemical properties[13].

Environmental Concern

Environmental concern surrounding PFAS stems from their widespread detection, high degree of environmental stability and mobility, and suspected toxicological effects on humans and the environment. Perfluorinated compounds, including PFAAs, are very stable and do not biodegrade. As a result, these compounds are found throughout the global environment. Trace amounts of perfluorinated compounds have been detected at remote locations like the Arctic, far from potential point sources[16]. Other studies have shown that some long-chain perfluorinated substances bioaccumulate and biomagnify in wildlife[17]. Because of this, higher trophic wildlife including fish and birds, and humans who consume them, can be particularly susceptible to any deleterious health effects posed by PFAS[18]. 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[1]. Recent fish and wildlife consumption advisories have been issued at certain locations in the United States associated with PFAS contamination[19][20].

Like other aspects of PFAS research, information on the toxicological effects of PFAS on humans is still emerging. PFOA and PFOS have half-lives of 2.1-8.5 years and 3.1-7.4 years, respectively, in humans[15]. PFAS typically accumulate in the liver, proteins, and the blood stream[2]. Toxicological and epidemiological studies of PFOA, PFOS and other PFAAs indicate potential association with a constellation of ailments including decreased fertility, increased cholesterol, suppression of response to vaccines, and certain cancers[15][21]. Both PFOA and PFOS are suspected carcinogens, but their carcinogenicity remains to be classified by the U.S. EPA[2]. The International Agency for Research on Cancer (IARC) has classified PFOA as a Group 2B carcinogen, i.e., possibly carcinogenic to humans[22][23]. The U.S. EPA published draft oral reference doses of 20 ng/kg-day for both PFOA and PFOS (based on non-cancer hazard)[2]. Drinking water ingestion, fish consumption, dermal contact with water, and (accidental) ingestion of or contact with contaminated soil are the exposure pathways of concern with respect to human health.

Uses and Potential Sources to the Environment

Due to their unique properties, including surfactant qualities, heat and stain resistance, and amphiphilic nature, PFAS are used widely by a number of industries, including carpet, textile and leather production, chromium plating, photography, photolithography, paper products, semi-conductor manufacturing, coating additives, and cleaning products[24][25]. Sources to the environment include primary manufacturing facilities, where PFAS is produced, and secondary manufacturing facilities, where PFAS is incorporated into products. PFAS are found in a variety of consumer products including food paper and packaging, furnishings, waterproof clothing, and cosmetics[26]. The presence of PFAS in consumer products has created an urban background concentration in stormwater, wastewater treatment plant influent[27], and landfill leachate[28].

An additional widely documented source of PFAS is AFFF. AFFF is as a Class B firefighting foam used to combat flammable liquid fires. AFFF was released in large quantities at firefighting training areas as part of routine handling, fire-suppression training and equipment testing, and during fire emergency responses. While all AFFF contains PFAS[29], the types and concentrations of PFAS in AFFF vary among manufacturers and manufacturing time periods. 3M AFFF products were made using an electrochemical fluorination process that produced a high percentage of PFAS as PFOS, while other formulations were made using a telomerization process and contain a different suite of PFAS.

Regulation

The U.S. EPA recently developed Drinking Water Health Advisory levels for PFOA and PFOS, replacing previously published provisional values[9]. However, no Federal enforceable drinking water standards have been set. Recent years have seen increased regulatory activity at the state level, with around 20 states having guidance or advisory levels for one or more PFAS compounds in various environmental media (drinking water, groundwater, etc.). New Jersey is the first state to have promulgated an enforceable maximum concentration level (MCL) for a PFAS by setting an MCL for PFNA in 2018. Several other states, particularly in the eastern United States, are moving towards setting MCLs for various PFAS. Regulatory levels set or proposed by states vary but the majority are equivalent to or lower than the Federal Health Advisory level of 70 parts per trillion (ppt) combined concentration of PFOA and PFOS. The regulatory landscape for PFAS is developing rapidly. A regularly updated repository of regulatory levels is maintained by the ITRC (Figure 4).

Figure 4. ITRC PFAS Fact Sheets: 1. Naming Conventions and Physical and Chemical Properties, 2. Regulations, Guidance, and Advisories, 3. History and Use, 4. Environmental Fate and Transport, 5. Site Characterization Tools, Sampling Techniques, and Laboratory Analytical Methods, and 6. Remediation Technologies and Methods.

Other regulatory actions have restricted the use and production of PFAS. 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[30][31].

Litigation

There have been many lawsuits filed with PFAS-related claims; some resulting in settlements in the hundreds of millions of dollars. In 2017 DuPont and Chemours paid nearly $700 million to settle 3,550 individual lawsuits claiming personal injury as a result of PFOA releases from DuPont’s former Washington Works manufacturing facility in Parkersburg, West Virginia. This settlement was reached after three of the lawsuits went to trial resulting in nearly $20 million in jury awards to the plaintiffs[32]. In 2018, 3M agreed to pay $850 million to settle a $5 billion natural resource damages claim related to PFAS impacts brought by Minnesota’s Attorney General[33]. In early 2019, numerous product liability lawsuits against former manufacturers of PFOS and PFOA and manufacturers of AFFF were consolidated into a multi-district litigation (MDL) pending before the U.S District Court of South Carolina[34]. Numerous additional PFAS-related lawsuits have been brought under common law tort, personal injury, product liability and natural resource protection laws across the United States. The proposed designation of PFAS as a hazardous substance under CERCLA[35] may have additional legal implications.

Sampling and Analytical Methods

Because of the presence of PFAS in many common consumer items and sampling materials, and the low reporting levels needed to compare to current regulatory guidelines, sampling for PFAS requires extra care to avoid cross contamination from other potential sources of PFAS. Most standard operating procedures and work plans advise avoiding the use of fluoropolymer-based (e.g., Teflon) components and recommend additional precautions related to sample containers, sampler clothing and handling of certain every-day items.

Commercial laboratories analyze PFAS in drinking water samples using the EPA-approved method 537.1, which consists of solid phase extraction and liquid chromatography with tandem mass spectrometry[36]. Samples collected from any environmental media other than drinking water require a modified version of 537.1 to quantify approximately 24 individual PFAS compounds. An EPA method for some of these other media, Method 8327, was released for public comment in summer 2019[37]. Some commercial laboratories can extend the target analyte list to include up to 40 compounds. Some commercial laboratories also offer an analytical method known as the Total Oxidizable Precursor (TOP) Assay, which provides a bulk measurement of PFAS mass in a sample, including that of oxidizable precursors[38][39]. 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)[26].

Fate and Transport

The processes of sorption and biotransformation as well as the presence of co-contaminants can affect the fate and transport of PFAS. It has been observed that PFAAs exhibit affinity for solid-phase organic carbon to varying degrees depending in part on chain length and structure, with long-chain compounds exhibiting a stronger affinity than short-chain and PFSAs exhibiting a stronger affinity than PFCAs for a given chain length[40]. Interactions with mineral phases, particularly ferric oxide materials, may also be important under certain conditions[41][42]. At present, empirical site-specific sorption estimates are recommended to accurately predict PFAS mobility[41]. PFAAs do not readily degrade in the environment. However, polyfluorinated forms may biotically or abiotically degrade to other intermediate forms and/or so-called “terminal,” recalcitrant PFAA forms, including PFOA and PFOS[43][44][45]. As a result, these degradable PFAS are sometimes referred as PFAA “precursors.” Remediation of co-contaminants, particularly using techniques involving oxidation, can enhance the degradation of precursors. Interactions between PFAS and non-aqueous phase liquids can retard PFAS migration[46]

Remediation Technologies

Due to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures, soil and groundwater remediation is challenging and costly. Research is still ongoing to develop effective remedial strategies. Treatment options for soil include 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. 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[47]. However, granular activated carbon has a relatively low capacity for PFAS 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 resins, and other sorbent materials as well as mixtures of clay, powdered activated carbon, and other sorbents[48]. Other methods for ex situ PFAS removal include high-pressure membrane treatment using nanofiltration or reverse osmosis[47][49][50]. Research into other PFAS treatment technologies, including in situ barriers (sequestration), biological treatment[51], advanced oxidation processes and in situ chemical reduction is ongoing.

Summary

PFAS are ubiquitous in a variety of industrial and commercial products, have been detected in many environmental media, pose potential risks to human and environmental health, and present challenges with respect to remediation. They are highly stable and mobile in the environment, may bioaccumulate and biomagnify in wildlife, and are the subject of litigation and regulatory actions at the local, state and Federal level. Health-based drinking water advisory levels are low, i.e., ng/L concentrations. As awareness of PFAS grows and regulatory criteria progress, site managers are conducting site investigations, improving analytical techniques, and designing and operating remediation systems. Current research, including that funded by SERDP/ESTCP, aims to demonstrate effective treatment technologies for PFAS and improve technology cost-effectiveness.

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See Also

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