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What’s GenX still doing in the water downstream of a Chemours plant?
Despite efforts to prevent the industrial fluoroether from getting into North Carolina drinking water, it’s still present. Scientists are racing to find out why
Larry Cahoon found out two weeks before most of his neighbors that their tap water held a cocktail of never-before-seen industrial chemicals.
In brief
Discovery of a class of industrial compounds called fluoroethers in public tap water last year shocked hundreds of thousands of North Carolina residents who had been drinking the tainted liquid. The source of that contamination is a Chemours fluoropolymer plant that discharged wastewater into the Cape Fear River. The facility now captures all its wastewater for disposal elsewhere. In response, amounts of the substances have dropped, but they haven’t disappeared. Researchers don’t know where the contaminants continue to come from or how they may have affected the health of people who consumed them, but they are conducting studies to find out.
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Last May, Cahoon invited a handful of scientists to talk with a local group working to restore striped bass and other migratory fish in North Carolina’s Cape Fear River. At that event, one of the panelists discussed a recently published study that found perfluorinated ethers in a municipal drinking water system that draws from the river (Environ. Sci. Technol. Lett. 2016, DOI:10.1021/acs.estlett.6b00398).
Cahoon, a University of North Carolina, Wilmington, biology professor who studies aquatic ecology, had read the paper and surmised that the chemicals came from a Chemours plant on the outskirts of Fayetteville, N.C. But the study did not name the town with the contaminated tap water.
The panelist, however, did name the locale: The affected city was Wilmington, N.C., said Detlef Knappe, a North Carolina State University engineering professor and coauthor of the paper.
“I had this ‘oh crap’ moment,” Cahoon says. More than a quarter-million people—including Cahoon and his family—get their drinking water from the stretch of the Cape Fear River that runs southeast from Fayetteville to Wilmington. Most of Cahoon’s neighbors in Wilmington learned about the fluorinated substances in their tap water a few weeks later, when the local newspaper, the Wilmington StarNews, launched an ongoing series of articles delving into the pollution.
“That’s when the shit hit the fan,” Cahoon says.
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The Wilmington water utility and North Carolina officials scrambled to stop the contamination. Standard drinking water treatment cannot remove the polyfluorinated ethers, so the state asked Chemours to halt a vinyl ether production process that generated the compounds. Later, after a spill at the plant, the state revoked the company’s wastewater discharge permit for its fluorochemical production unit. Chemours now hauls all fluorochemical production wastewater from the Fayetteville facility via tanker truck and rail to Deer Park, Texas, for disposal in a deep injection well, the company told the North Carolina Department of Environmental Quality (DEQ) and the U.S. Environmental Protection Agency in November.
But scientists are still finding fluoroethers in the river. Where the chemicals are coming from is a mystery. And no one knows whether exposure to these chemicals might harm people’s health or the environment.
Despite repeated requests, Chemours did not respond to C&EN’s inquiries for this story.
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Fluoropolymer factory
Credit: C&EN/Shutterstock
The Cape Fear River runs through southeastern North Carolina before emptying in to the Atlantic downstream of the city of Wilmington.
The Chemours plant sits on 2,870 hectares in a rural area south of Fayetteville, near the west bank of the Cape Fear River. The waterway flows more than 110 km beyond the facility before reaching Wilmington. South of the city, the river broadens into an estuary about 50 km long that empties into the Atlantic Ocean.
For decades, the plant used the ammonium salt of perfluorooctanoic acid (PFOA) as a surfactant that aids in the polymerization of fluoropolymers. 3M supplied DuPont with PFOA for many years. But 3M phased out its U.S. manufacture of the surfactant between 2000 and 2002 amid rising concerns about the health effects of perfluorinatedchemicals with eight-carbon or longer chains, including PFOA, that are highly persistent in the environment.
With PFOA coming off the market, DuPont developed a substitute surfactant in the form of an ammonium salt of a fluorinated ether acid. The company called its new product GenX.
Before DuPont began producing GenX on a commercial scale, the company struck a legal agreement with EPA under the federal Toxic Substances Control Act. That January 2009 consent order allowed DuPont to manufacture GenX’s parent acid—an asymmetric molecule dubbed hexafluoropropylene oxide dimer acid fluoride (HFPO-DA fluoride)—and GenX itself.
Credit: Courtesy of Mark Strynar and Laurence Libelo/U.S.EPA
GenX and its precursor acid hydrolyze into HFPO-DA.
The 72-page order, a redacted version of which was made public by investigative news website the Intercept in 2016, lays out detailed worker protection requirements for the manufacture and use of the chemicals. A single sentence describes the control of water discharges and air emissions of the two fluorochemicals: “The company shall recover and capture (destroy) or recycle the [two substances] at an overall efficiency of 99% from all the effluent process streams and the air emissions.
With the consent order in place, DuPont began manufacturing GenX at the North Carolina factory.
DuPont called GenX a “sustainable replacement” for PFOA in a 2010 marketing brochure. That document describes GenX as having “a favorable toxicological profile” and claims it was eliminated rapidly from the bodies of laboratory animals. GenX is manufactured using “unique environmental exposure control technologies that reduce the potential for environmental release and exposure,” the brochure continues.
The brochure also notes that GenX would not break down easily if it was released into the environment. “The goal of the DuPont GenX exposure control strategy is to contain the new processing aid within the manufacturing site and to minimize worker exposures,” it states. This strategy consists of a variety of environmental engineering controls, including filters and scrubbers, that can recover or recycle GenX, the brochure says.
Concerned about fluorochemical contamination of their drinking water, protesters gathered outside a North Carolina government office in June 2017.
The fluoroethers in the Cape Fear River might have remained undiscovered but for curious scientists applying both a modern approach to environmental research and old-fashioned analytical chemistry.
The pioneer in identifying the fluoroether pollution is Mark Strynar, an EPA research scientist. He focuses on developing analytical chemistry methods for the detection of synthetic chemicals, particularly fluorinated compounds, in the environment. As part of that work, which began in 2012, he led a team of researchers from public and private institutions using a relatively new mass spectrometry technique called nontargeted analysis. This method involves detecting a broad array of chemicals, known and unknown, in the environment. It contrasts with traditional targeted analyses that look for specific substances in waterways, soils, human urine, air, household dust, and other media.
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For a researcher seeking a place to study synthetic chemicals in the environment, the Cape Fear River was a rational place for Strynar to target. The river is a short drive from his workplace, EPA’s National Exposure Research Laboratory in Research Triangle Park, N.C. The waterway also has a history of contamination with two eight-carbon perfluorinated compounds—PFOA and another phased-out substance, perfluorooctane sulfonic acid (PFOS). In addition to Chemours’s use of PFOA as a polymerization surfactant, these two substances were formerly used in firefighting foams and to coat textiles, he says. The river also receives effluent from municipal wastewater treatment facilities, which can be sources of fluorochemicals washed from consumer and commercial goods.
Strynar and his team used high-resolution mass spectrometry to analyze samples collected in 2012 from the Cape Fear River. They identified a suite of novel polyfluorinated compounds downstream of the Chemours plant (Environ. Sci. Technol. 2015, DOI:10.1021/acs.est.5b01215).
The toughest part of this work, Strynar says, was puzzling out the identities of the fluorocompounds detected in the river. “It’s not simple, it’s not fast, it’s a long and arduous process, and it took a lot of people,” he says.
Fluoroether stew
To make communication with the public easier, DEQ and researchers generally refer to the mixture of related fluorochemicals found in the Cape Fear River as GenX.
When GenX contacts water, it releases the ammonium group to become HFPO-DA. Because HFPO-DA is a strong acid, it deprotonates at pH levels found in the environment, NC State’s Knappe tells C&EN. That anion has become the Cape Fear River’s most famous fluorochemical.
“It’s really hard to tell people what I found was HFPO dimer acid. That sort of doesn’t roll off the tongue,” Strynar says. Knappe agrees: “I talk about GenX because it’s just easier to say.”
The HFPO-DA anion was one of the fluorocarbons Strynar’s team initially found in the greatest concentrations in the river downstream from the Chemours plant. The researchers also detected other fluoroethers in the water. These include perfluoro-3,5,7-trioxaoctanoic acid (PFO3OA), which is structurally similar to the phased-out chemical PFOA but has ether groups along the carbon chain, as well as two more related compounds: perfluoro-3,5-dioxahexanoic acid (PFO2HxA) and perfluoro-2-methoxyaceticacid (PFMOAA).
Though the Fayetteville plant produces GenX as a commercial product, the facility may have discharged some form of HFPO-DA into the river for years. “The same chemical is also produced as a byproduct during other manufacturing processes and it may have been present in the environment for many years before being produced commercially as GenX,” DEQ says.
According to news reports from June, Kathleen O’Keefe, Chemours’s director of product sustainability, said the substances are by-products from the part of the facility that manufactures polyvinyl ethers and had periodically been discharged to the river since 1980. Neither O’Keefe nor a Chemours global communications official responded to C&EN’srequests to confirm the news reports.
The 2009 deal with EPA that allows the manufacture of HFPO-DA and GenX specifies that requirements for capture, destruction, or recycling do not apply to the chemicals “when they are produced, without separate commercial intent, only as a ‘byproduct.’ ”
Toxicity unclear
Worrying Wilmington residents and public health officials is that scientists don’t know whether or how drinking water tainted with GenX-related chemicals has affected or might affect people’s health.
To provide guidance on drinking water safety, the North Carolina Department of Health & Human Services turned to the European Chemicals Agency, one of the few sources of toxicity data for GenX. DuPont registered the compound for manufacture and use in the European Union under the Registration, Evaluation, Authorisation & Restriction of Chemicals law, or REACH. Data that DuPont submitted to the EU agency to support that registration included results of a two-year chronic toxicity and carcinogenicity study in laboratory rats. Using this information, the EU agency determined that ingesting 1 mg of GenX per kg of body weight perday would have no observable adverse effects.
Although GenX—or, specifically, the HFPO-DA anion—has gotten the most attention, “I’m not sure whether it’s the most toxic in the mix of chemicals we’ve found,” Knappe says. He is particularly concerned about two by-products of Nafion manufacture that Strynar’s team found in the river. These are longer-chain fluorochemicals than HFPO-DA and are likely more bioaccumulative than the GenX-related compounds, Knappe says. Given the comments by Chemours’s O’Keefe, Knappe wonders whether the plant might have discharged Nafion by-products into the Cape Fear River for decades, just as it released the HFPO-DA and related chemicals produced in the manufacture of vinyl ethers.
Nafion by-products are appearing in the Cape Fear River downstream of the Chemours plant.
HFPO-DA, GenX, and related compounds; the Nafion by-products; and various other per- and polyfluoroalkyl substances are collectively called PFASs. For its part, EPA says that exposure to PFASs can cause a number of adverse health effects, on the basis of laboratory studies that exposed monkeys, rats, and mice to PFOA or PFOS. Some studies in humans show that certain PFASs may harm the development of fetuses and children, interfere with hormones and decrease fertility, raise cholesterol levels, hamper the immune system, and increase a person’s chance of developing cancer, EPA says.
Nevertheless, EPA currently has no national regulation or guidance for GenX-related compounds in drinking water. In December, however, EPA announced that a panel of scientists from across the agency is addressing PFASs. That group is bringing together scientists from EPA’s water and research programs as well as its air, chemicals, and waste offices, the agency says. EPA says it will work closely with states and tribes on PFAS pollution.
Chinese researchers have also raised flags about these chemicals. Results of cellular and protein assays of liver function suggest that HFPO-related chemicals and other substitutes for PFOA and PFOS could cause greater liver toxicity than the compounds they’re replacing, says a study led by Jiayin Dai, who heads an ecotoxicology group at the Chinese Academy of Sciences’ Key Laboratory of Animal Ecology & Conservation Biology. The researchers found that replacing hydrogen with fluorine might reduce toxicity, but inserting oxygen atoms and increasing chain length “seem to be able to induce more serious toxicities,” the study says (Arch. Toxicol. 2017, DOI:10.1007/s00204-017-2055-1).
And a study published by researchers in Sweden at the end of January concludes that GenX is more toxic than PFOA, on the basis of a computer model that analyzed data from studies in laboratory rats. When differences in the rates of distribution and elimination of these chemicals in the body are accounted for, the study says, “some fluorinated alternatives have similar or higher toxic potency than their predecessors.” (Environ. Int., 2018, DOI: 10.1016/j.envint.2018.01.011).
A two-year, $275,000 grant awarded late last year to NC State researchers by the U.S. National Institute of Environmental Health Sciences should reveal more about these compounds’ toxicity in humans. Principal investigator Jane Hoppin, an epidemiologist and deputy director of NC State’s Center for Human Health & the Environment, says the work involves studying the blood and urine of 300 residents of the Wilmington area whose tap water is supplied by the local water company, the Cape Fear Public Utility Authority, for the presence of HFPO-DA anion, the two Nafion by-products, and a suite of other polyfluorinated substances.
These chemicals have never been measured in people before, Hoppin tells C&EN. Researchers will be looking at the quantity of PFASs people have in their bodies as well as their lipid levels and thyroid and liver functions, she says. Previous epidemiology studies with other PFASs found effects in these metabolic measures that were linked to exposure.
A key issue researchers hope to answer in the North Carolina study is how long these substances remain in people’s bodies, Hoppin says. Nothing is known about the half-life of GenX-related compounds in humans, she explains. She expects to have initial results from the study in late February, although publication will take longer.
In October, lawyers for people who drank the contaminated water in North Carolina filed a class-action suit against Chemours and DowDuPont. The plaintiffs want the companies to provide monitoring for health problems that may be caused by the fluorinated compounds they ingested.
Chemours is no longer discharging fluorochemical production wastewater into the Cape Fear River from its Fayetteville Works site, shown here in a 2017 photo.
Much of the fluorinated compound pollution in the Cape Fear River will likely be addressed through Chemours’s current capture of all its fluorochemical process wastewater for disposal, Knappe says.
If that practice continues, the main concern about future pollution in the river might be spills at the plant, he suggests. The Cape Fear River water flows from the Fayetteville plant to Wilmington in two to three days. If Chemours can give an early warning about a fluorochemical spill to downstream drinking water utilities, “they can turn off the intake and rely on stored water” until the contamination passes, keeping municipal water supplies untainted, he says.
But wastewater and spills may not be the only sources of fluorochemical contamination of the environment.
Researchers are also taking a closer look at what Chemours is releasing into the atmosphere. Data made public by DEQ show that the Fayetteville plant has emitted at least 244 kg of HFPO-DA fluoride into the air each year since 2013, peaking in 2015 with more than 300 kg.
“The dimer acid fluoride rapidly reacts with water to form HFPO-DA,” Knappe tells C&EN. “Once deposited on the ground, HFPO-DA can percolate with rainwater through the soil into the groundwater.”
After finding that 13 environmental monitoring wells at the Chemours plant had levels of the HFPO-DA above the state’s public health goal of 140 ppt, DEQ and Chemours began to test wells at private residences near the facility. Those tests have turned up the HFPO-DA anion along with PFMOAA, PFO2HxA, PFO3OA, and Nafion by-products in household wells on property near the Chemours plant, Knappe says. One well had 1,300 ppt of HFPO-DA; another had 1,200 ppt. Additionally, although the Chemours plant is west of the Cape Fear River, tests detected HFPO-DA in private well water at residences east of the waterway. A small lake several kilometers upstream from the Chemours plant and about a kilometer from the river bank had 915 ppt of HFPO-DA, DEQ reported in November. And a separate recreational lake several kilometers from the plant in a different direction showed 620 ppt of HFPO-DA.
Such widespread contamination away from the plant and the river further points to airborne spread of the compounds, Knappe says. Precipitation could be one way the substances get from the air to the ground. Preliminary studies in recent weeks by a team of chemists at UNC Wilmington found HFPO-DA anion in rainwater samples from a National Science Foundation-funded collection station at the campus.
Scientists are also concerned that even though Chemours is capturing all its fluorochemical process wastewater, the substances that Strynar’s team initially found in the river are still in the waterway near Wilmington at detectable levels, Knappe says.
“Where is it coming from?” asks Knappe, who is helping the state government evaluate emerging contaminants such as fluorocarbons as part of North Carolina’s Science Advisory Board. If an aquifer beneath the plant that is hydrologically connected to the river is contaminated, then Chemours would need to clean up the polluted groundwater. Or, if precipitation runoff is carrying pollution from the plant to the river, then the facility needs to improve its storm-water management, he says.
But if the fluorocarbons are tied up in river sediments and slowly being released—as hydrophobic and environmentally persistent compounds often are—“that’s a more difficult question,” Knappe adds.
The team of chemists that found the HFPO-DA anion in rainwater is also studying the issue of poly- and perfluorocarbons in the river’s sediments. Led by chemistry professor Ralph Mead, the researchers have collected samples upstream of the Chemours plant, at the mouth of the Cape Fear River, and at points in between. They are now undertaking labor-intensive work of sediment extraction with subsequent cleanup to isolate and identify PFASs through targeted and non targeted liquid chromatography/mass spectrometry. The team is also working to understand the environmental transport and fate of PFASs, both locally and globally.
The sediment work raises questions about Wilmington’s drinking water system. If the fluorocarbon compounds attach to river sediment, are they also in the grains that collect in water towers and water heaters? wonders UNC Wilmington biologist Cahoon. He also worries about biofilms in the water distribution system, especially in pipes farthest from the filtration plant that pumps out freshly disinfected water. “This stuff sticks to proteins in biofilms,” Cahoon says of the HFPO-DA anion.
Meanwhile, the fluorochemicals keep popping up in surprising places. North Carolina officials recently checked the honey of a hobbyist beekeeper who lives near the Chemours plant. The honey contained 2,070 ppt of HFPO-DA, DEQ tells C&EN. The beekeeper voluntarily discarded his honey, the state agency says. Researchers don’t know how the chemical got into the sweet liquid.
“That certainly raised eyebrows,” Knappe says of the honey finding. “How far does this contamination really spread?” he wonders aloud. “Not just through the air and water, but also through the food web. It’s very messy.”
Wanted: Fluorochemical reference standards
Credit: Cheryl Hogue/C&EN
Strynar is looking for chemists to synthesize fluorochemicals needed for environmental analysis.
When researchers discover a new chemical in the environment, they need a reference sample of known purity to do further research on the substance. Such reference standards are necessary to calculate concentrations of chemicals in environmental samples, conduct toxicology studies, or carry out environmental fate and transport testing.
But suppliers of chemical standards sometimes don’t have novel industrial chemicals, in particular those that are unintentional by-products of manufacturing processes. Researchers can measure the concentration of only some of the fluorochemicals in the Cape Fear River because they don’t have standards for comparison, says EPA scientist Mark Strynar.
Chemours supplied standards for the two Nafion by-products found in the Cape Fear River to Strynar in November. Strynar is seeking standards for perfluoro-3,5,7-trioxaoctanoic acid (PFO3OA), perfluoro-3,5-dioxahexanoic acid (PFO2HxA), and perfluoro-2-methoxyacetic acid (PFMOAA). “Those compounds need to be synthesized,” Strynar says. “Without that, our work is sort of at a standstill.”
“There’re people out there that can do that synthesis and they can make these available as chemicals for us to purchase,” Strynar says in a pitch to the chemistry community. “It doesn’t have to be 99.9% pure,” he says.
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