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The Shrinking Case For Fluorochemicals

As the long-alkyl-chain fluorocarbons found in many household products are replaced with short-chain ones, debate over safety continues

by Stephen K. Ritter
July 13, 2015 | A version of this story appeared in Volume 93, Issue 28

This year marks the end of a program launched by the Environmental Protection Agency to eliminate the production and use of one of the chemical industry’s most important classes of compounds: perfluorooctanoic acid (PFOA), along with its precursors and analogs.

The program, launched in 2006, was prompted by years of pressure by environmental and consumer groups and regulatory scrutiny of the safety of the long-alkyl-chain fluorocarbons, which are used to treat the surfaces of metals, paper, carpet, and fabrics to impart water-, soil-, and oil-repellent properties. They are also used to make abrasion-, chemical-, and fire-resistant polymers and are found in products as diverse as nonstick cookware, grease-wicking pizza boxes, airplane hydraulic fluid, stain-resistant carpet, and breathable rain jackets.

Unfortunately, the properties that make the compounds so useful also make them persistent in the environment. The chemicals and their degradation products are now found in places ranging from pristine areas of the Arctic to sludge in municipal wastewater treatment plants. Low levels of the compounds have contaminated nearly every corner of the food chain, from herring to humans.

Research has shown that the compounds can cause cancer and disrupt sexual development in lab animals. Still-emerging epidemiological evidence suggests the compounds might cause or contribute to similar problems in people, prompting scientists to conclude that the risk of continuing to use the compounds is too great.

Graphic showing structures of long-alkyl-chain fluorinated substances that are being phased out of product manufacture and the fluorinated substances that are replacing them.
Credit: Shutterstock/C&EN
Long-fluoroalkyl-chain compounds used in many types of industrial and consumer products are being replaced by short-chain versions (only a few examples of each are shown).

The industry is voluntarily doing away with the long-chain compounds and replacing them with short-chain analogs that are still persistent but that are much less bioaccumulative and therefore expected to be less toxic. Even so, now that the long-chain compounds are making their exit, some scientists and advocacy groups are issuing calls for the short-chain compounds to be discontinued. There remains disagreement, however, about whether the replacement compounds are safer than their predecessors.

Long-chain fluoroalkyl chemistry had its beginning more than 60 years ago. 3M’s Scotchgard brand of stain-protection products made with perfluoroalkyl sulfonamidoethanols was one of the first to hit the market. This family of compounds is identified by perfluorooctanesulfonic acid (PFOS), which is a sulfonamidoethanol degradation product.

PFOA was another of the early products. Its ammonium salt is used in small amounts as a surfactant to help solubilize fluorinated monomers during emulsion polymerization, which is used to make plastics such as DuPont’s Teflon brand of poly(tetrafluoroethylene). PFOA and related carboxylic acids are also degradation products of fluorotelomer alcohols, which are tetrafluoroethylene-based compounds used to attach fluoroalkyl groups to surfactants, polymers, and material surfaces.

Chemists attribute PFOS and PFOA’s armorlike properties to the eight carbons in their fluoroalkyl chains. Such chains have the rigidity and steric properties needed to optimize water and oil repellency.

When it became clear in the 1990s that PFOS was accumulating in people and might cause health problems, 3M accepted a deal with EPA to voluntarily terminate production of PFOS-related products. The firm unveiled a new version of Scotchgard, reformulated with shorter chain perfluorobutane-based chemistry.

Scientists had discovered a tipping point: Compounds with six or fewer fluorinated carbon atoms work nearly as well as the longer chain versions. However, their bioaccumulation potential is significantly reduced because shorter, less rigid chains boost their water solubility. Perfluorobutane sulfonate, the degradation product for 3M’s new formulation, has a half-life in people of about one month. PFOS, on the other hand, has a half-life of about four-and-a-half years. All other things being equal, the shorter half-life should reduce exposure time and lower the potential toxicity.

These findings led EPA to examine whether PFOA, which has a half-life in humans of about three years, presents the same concerns. As a result, EPA and the eight major companies that make or use PFOA launched the 2010/2015 PFOA Stewardship Program. The companies—Arkema, Asahi, BASF (successor to Ciba), Clariant, Daikin, DuPont, 3M/Dyneon, and Solvay Solexis—committed to reducing global facility emissions and product content of PFOA compounds by 95% relative to 2000 levels by the end of 2010. The companies also committed to fully eliminate PFOA compounds by 2015, leading the firms to start switching over to the short-chain replacements.

“EPA’s voluntary stewardship program is an important accomplishment,” says Thomas H. Samples, director of risk management at Chemours, DuPont’s former performance chemicals business, which includes the fluorochemicals. “The voluntary program allowed the industry the opportunity and the time to reduce PFOA emissions as we undertook research to develop alternatives that meet product performance needs. Not only have we taken PFOA out of the picture, we learned new technology to minimize emissions of the alternatives.”

Replacing PFOA as a surfactant in polymer production was the hardest, Samples notes. The company now uses a fluoroether product with four fluorinated carbons. “The replacement materials had to be qualified at every step in our customers’ supply chain and their customers’ supply chain, all the way to the consumer, to make sure there were no gaps in performance.”

DuPont met the stewardship goals for 2010, Samples notes, and in 2013 stopped manufacturing PFOA and ceased using it to manufacture fluoropolymers. By the end of 2014, the company completed conversion of its fluorotelomer-based product line to short-chain products. The other seven companies party to the stewardship agreement are expected to meet the goals by the end of this year.

Federal government data show that PFOS and PFOA concentrations have been dropping in the blood of the general population, Samples adds. “This program has had a substantial global impact,” he says. “I believe it worked faster and more efficiently than any regulation would have.”

But even as the fluorochemicals industry is doing away with the long-chain compounds, some scientists and environmental groups are calling for the short-chain replacements to be gone, too. For example, last year a group of seven environmental scientists who study perfluorochemicals led by Martin Scheringer of the Swiss Federal Institute of Technology, Zurich, issued the Helsingør Statement (Chemosphere 2014, DOI: 10.1016/j.chemosphere.2014.05.044). In it, the scientists outline their concerns about the potential long-term environmental impacts of transitioning to the short-chain alternatives, namely that one set of environmentally persistent compounds will be replacing another.

Earlier this year, the Helsingør scientists joined with additional scientists and policy experts to draft a policy document called the Madrid Statement (Environ. Health Perspect. 2015, DOI: 10.1289/ehp.1509934). This document, signed by more than 200 scientists so far, reiterates the points made in the Helsingør Statement and is designed to inform policy-makers and the public about the risks of the transition. The Madrid Statement argues that these risks makes it imperative that scientists, industry, governments, and consumers share information. The statement further outlines ways they can work toward limiting the use of fluorochemicals and developing safer alternatives.

They say more information is needed on the structures, properties, uses, and health and safety effects of the fluorinated alternatives—chemical companies often supply incomplete data and are vague in their descriptions, and regulatory agencies don’t make public all proprietary information.

For example, in 2005 EPA fined DuPont $16.5 million for failing to report certain PFOA health-effects studies the company had conducted over the previous 25 years. The Madrid Statement says that such tactics force publicly funded researchers to spend years and significant sums investigating the properties, effects, and toxicity of every chemical and commercial product, which is a heavy cost burden on society.

When the Madrid Statement was issued in May, it was accompanied by a rebuttal by Jessica S. Bowman, executive director of the FluoroCouncil, which is a branch of the American Chemistry Council, the chemical industry’s main trade group (Environ. Health Perspect. 2015, DOI: 10.1289/ehp.1509910).

Bowman says the FluoroCouncil supports the call to action from the global community to restrict long-chain perfluoroalkyl compounds. But the Madrid Statement “fails as a policy statement,” she adds, “because it doesn’t acknowledge that fluorotechnology is essential for many aspects of modern life and ignores substantial scientific data that support the conclusion that short-chain compounds are expected to pose no significant risk to human health and the environment.”

Any claim that insufficient safety data are publicly available, she says, “is simply incorrect.” She also points out that decisions on the societal acceptability of strategic materials such as the fluoroalkyl substances can’t be made on a single attribute such as persistence.

But Scheringer argues that persistence is precisely the problem. Although the short-chain compounds are cleared from the body more quickly than the long-chain versions, the fact that they are always present means continuous exposure, which is cause for concern, he says.

For now, the compounds might not be causing any detectable damage. But over time, environmental levels of the compounds could increase to the point that they start becoming a problem. Eventually, he suggests, levels could become out of control, and it would be extremely difficult if not impossible to do anything about it. Adopting that philosophy, the scientists of the Helsingør and Madrid Statements assert that the best option going forward is to limit use of the fluoroalkyl-based chemicals to essential purposes and not use them in common consumer products.

Developing nonfluorinated alternatives is a tough nut to crack because of the fluorochemicals’ broad range of uses—replacements are easy in some applications, but not in others. For example, in textiles that require only water repellency, polyether/polyester fabrics work well. Alternatives to fluorocarbon surface finishes include hydrocarbon waxes and paraffins and silicones.

But when it comes to oil repellency, the nonfluorinated options don’t stack up. “We still need the high-performance fluoro­telomer materials to meet that need in the market,” Chemours’s Samples says.

Environmental chemist Scott A. Mabury of the University of Toronto takes yet another view. Although Mabury agrees more needs to be done to protect the environment, he believes calling for bans on chemicals “is bad policy because bans are counterproductive to finding real solutions.”

Mabury has spent nearly 20 years studying how widespread perfluorochemicals have become in the environment and unraveling their degradation pathways. He has declined to sign the Madrid Statement.

“The fluorochemicals industry has been doing great to clean up its chemistry and by introducing the short-chain alternatives that are less bioaccumulative and are clearly better for reducing exposure to people and the environment,” Mabury says.

Mabury applauds the EPA stewardship program and related government efforts for setting performance standards. A ban would remove the incentive to create successively better, environmentally benign generations of chemicals. For example, he says, chemists originally thought that matching fluoroalkyl materials’ chemical and thermal performance would require at least seven fluorinated carbons. But 3M showed it could be done with four, and the rest of the industry followed suit.

“The goal should be to introduce nonpersistent alternatives that still provide the exquisite surface properties that fluorochemicals are known for but that can fully degrade in the environment,” Mabury says. To that end, Mabury’s group is working on developing a fluorinated surfactant that has been designed to completely defluorinate under normal environmental conditions to form carbon dioxide and fluoride ions.

“We are chemists. We should be pushed to innovate and be better chemical architects to design molecules that function as intended and avoid creating chemical pollution,” Mabury says. “Many people would not want to do without the fluorochemical-based products they have come to appreciate. The challenge is not to deny the fundamental ability of chemists to be creative but to keep working at it.”  


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