In the last few years a class of chemicals known as perfluoroalkyl substances (PFAS) have been identified as emerging contaminants by the U.S. EPA. An emerging contaminant is a chemical, or in this case, a class of chemicals, that has a perceived or is a potential threat to human health or ecological receptors. A chemical may also be considered to be an emerging contaminant due to insufficient data to assess health hazards, or when a new pathway to human exposure has been identified. The two constituents in this class of chemicals that are receiving the most attention are: perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA).
In May 2016, the U.S. EPA issued a drinking water health advisory for PFOS and PFOA and issued a follow-up memorandum in November 2016 to clarify the appropriate application of the health advisory. Health advisories are non-enforceable, but are used to provide technical information on potential health effects to public health officials regarding contaminants that can cause adverse health effects and are known or anticipated to be to present in drinking water. They may also contain information on analytical methods or treatment technologies to remove the contaminant. The U.S. EPA health advisory level for PFOA and PFOS offers a margin of protection from adverse health effects due to exposure to these constituents in drinking water.
BACKGROUND
PFAS are similar to another class of chemicals known as perfluorocarbons. Perfluorocarbons contain only carbon and fluorine atoms, whereas PFAS can contain oxygen, nitrogen, hydrogen, and/or sulfur. The carbon-fluorine bond is very strong and metabolically and environmentally stable (USEPA 2016a). PFOA was first produced in the late 1930s by Minnesota Mining and Manufacturing (3M). DuPont began purchasing the product, which they called C8, to produce replacements for toxic refrigerant gasses such as ammonia and sulfur dioxide. However, one of the materials tested, tetrafluoromethane, polymerized into a powder that was found to be heat resistant, slippery, and chemically inert. The resulting polymer, polytetrafluoromethane, was branded Teflon® by DuPont (Chemours). DuPont used C8 as an anti-clumping agent during the production of Teflon®.
In the mid-1950s, 3M began producing PFOS, which could repel water, stains, and oil/grease (USEPA 2016b). In addition, this chemical had foaming properties used to create an aqueous film forming foam (AFFF). 3M began selling Scotchgard Protector, which contained PFOS. Other uses included: carpets, leathers, textiles, upholstering, paper packaging coating additives (e.g. pizza boxes, fast food/french fry containers, drink containers, bakery, and candy wrappers), and as a waterproofing agent (EPA 2016b). In the early 1960s, the U.S. Naval Research Center began experimenting with AFFF as a hydrocarbon firefighting agent which was used on all U.S. aircraft carriers and at refineries and major airports (NRL). The U.S. military is in the process of replacing the PFOS containing foam systems.
HEALTH AND ENVIRONMENTAL CONCERNS
According to papers filed in a West Virginia court, the location of the Washington Works DuPont facility where Teflon® is manufactured, DuPont was concerned about the health effects of C8 (PFOA) as early as 1961. According to a Columbus Dispatch article dated February 16, 2003, medical studies conducted by DuPont and 3M during the 1970s and 1980s indicated that C8 would bioaccumulate in human blood, wouldn't break down in the environment, and long term health effects including liver damage, reproductive and developmental defects, and cancer, were linked to C8. Based on these data, DuPont established a ''community exposure standard'' in 1991 of 1 part per billion (ppb, approximately one microgram per liter [µg/l]) in drinking water.
In Ohio, C8 was detected in drinking water in Pomeroy, located 70 miles downriver from the DuPont plant, and 4 miles upriver in Belpre, Ohio, as a result of C8 air emissions washing out during rain events. The highest concentrations found at that time were in the wells of the Little Hocking Water Association well field, located directly across the Ohio River from the DuPont Washington Works plant. Tests conducted in 2002 by DuPont contractors revealed the water contained concentrations of C8 twice as high as DuPont's community standard of 1 ppb. In October 2001, the U.S. EPA issued a Consent Decree that specified DuPont would have to provide alternative sources of drinking water should concentrations of C-8 be found at or above 14 ppb in public water systems or or private drinking water wells in the region. In 2002, the state of West Virginia and private scientists concluded the safe level of C8 in water was 150 ppb, which the Ohio Environmental Protection Agency (OEPA) endorsed (Columbus Dispatch).
On January 8, 2009, the U.S. EPA issued Provisional Health Adversaries for PFOA and PFOS. The U.S. EPA continued to study the toxicity of PFOA and PFOS. Based on the toxicological data developed, the May 2016 lifetime drinking water Health Advisory for PFOA and PFOS were determined to be 0.07 µg/l combined for both chemicals. This is similar to the concentration of approximately 3 to 4 “average” size (50 milligrams) grains of table salt in an Olympic-sized swimming pool. At this concentration, the U.S. EPA believes adverse health effects are not anticipated to occur over a lifetime. There are not currently U.S. EPA soil advisory levels for these chemicals.
ENVIRONMENTAL CONCERNS
Between 2000 and 2002, PFOS was voluntarily phased out of production by 3M, the primary manufacturer. The U.S. EPA also limited the manufacture and import of PFOS and required a review of its use. Limited exceptions were allowed if no viable alternatives were available. Scotchgard was re-formulated with the four-carbon cousin of PFOS.
In 2006, eight manufacturing companies agreed to phase out PFOA by the end of 2015. According to the U.S. EPA, the eight companies succeeded in phasing out PFOA by the 2015 deadline.
However, PFOA and PFOS are environmentally persistent. Due to the extensive historical use, residual contamination exists in areas where these chemicals were manufactured, used, and disposed. As an emerging contaminant, there are only health advisory concentrations for drinking water ingestion. There are not currently Federal advisory concentrations for other human exposure pathways, such as direct contact with soil or water, soil leaching to groundwater, or soil/groundwater to indoor air (vapor intrusion).
ANALYTICAL TESTING AND TREATMENT
In 2012, Pace Analytical in conjunction with the U.S. EPA, developed U.S. EPA Method 537 to test for PFAS in soil and water using liquid chromatography and tandem mass spectrometry. Currently this analytical method reports approximately 20 compounds. This analytical method costs several hundred dollars per sample due to the very low detection levels required to meet the 0.07 µg/l U.S. EPA health advisory.
PFAS cannot be removed by boiling water; however, there are options available to reduce the concentrations. Public systems can dilute the contaminant concentration by blending water from other wells/sources, close contaminated wells, re-locate well fields and/or surface water intakes, or treat the water with granulated activated carbon or reverse osmosis engineered to remove PFOA and PFOS. There are very few case studies on remedial technologies for soil; however, it appears persulfate-based reagents appear to be promising.
REFERENCES
Columbus Dispatch. 2003. INTERNAL WARNINGS Industry memos show DUPONT knew for decades that a chemical used to make Teflon is polluting workers and neighbors. Published February 16, 2003.
Chemours. 2015. History of Teflon®. https://www.chemours.com/Teflon/en_US/products/history.html
NRL. 2015. U.S. Naval Research Laboratory. Aqueous Film Forming Foam. https://www.nrl.navy.mil/accomplishments/materials/aqueous-film-foam/
USEPA (U.S. Environmental Protection Agency). 2009a. Provisional Health Advisories for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS). US Environmental Protection Agency, Office of Water. Washington, DC. Accessed May 2016. https://www.epa.gov/sites/production/files/2015-09/documents/pfoa-pfos-provisional.pdf
USEPA. 2009b. Fact Sheet DuPont Agrees to Lower Limit Of PFOA in Drinking Water. US Environmental Protection Agency, Office of Water. Washington, DC. March 2009. https://www.epa.gov/sites/production/files/2016-05/documents/dupont-fs0309.pdf
USEPA (U.S. Environmental Protection Agency). 2016a. Drinking Water health Advisory for Perfluorooctanoic Acid (PFOA). EPA 822R16005. U.S. Environmental Protection
Agency, Washington, DC. May 2016.
USEPA (U.S. Environmental Protection Agency). 2016b. Drinking Water health Advisory for Perfluorooctane Sulfonate (PFOS). EPA 822R16004. U.S. Environmental Protection
Agency, Washington, DC. May 2016.
Published: August 21, 2018