Increasingly found in drinking water, food, soils, and people’s bodies, per- and polyfluoroalkyl substances (PFAS) are industrial chemicals that essentially never break down in the environment. Cleaning up PFAS pollution is a headache because the compounds, designed to be extremely durable, are difficult to destroy in incinerators and can leach from landfills. The handful of nonpolymeric PFAS that toxicologists have studied cause adverse effects to livers and thyroids of laboratory animals.
To halt the ongoing buildup of PFAS in the environment, an international research team proposes that society move away from these “forever chemicals.” It is calling for an orderly elimination of PFAS-containing products from commerce (Environ. Sci.: Processes Impacts 2019, DOI: 10.1039/c9em00163h).
Take dental floss coated with the PFAS polymer polytetrafluoroethylene (PTFE), for example. PTFE allows the narrow ribbon to slip easily between close-pressed teeth. The researchers say consumers could easily opt for one of the many other types of flosses on the market. Eliminating products such as PFAS-coated dental floss would end environmental contamination from not only the individual items but also other PFAS used to manufacture them.
But the researchers are not calling for an immediate ban to all uses of PFAS. Instead, they recommend differentiating among the thousands of PFAS-containing products on the market according to how critical their use is and the availability of suitable replacements. Some products containing these chemicals—for example, perfluorosulfonic membranes that confer flame resistance to protective clothing worn by workers in the oil and gas industry—are essential and have no substitutes.
An international group of researchers is proposing phasing out the use of per- and polyfluoroalkyl substances (PFAS) according to whether the chemicals provide properties that are necessary for health and safety. This team suggests sorting products into three categories.
Uses that are not essential for health or safety or the functioning of society. The use of substances is driven primarily by market opportunity. PFAS use can be phased out or banned.
Example: Perfluorodecalin in cosmetics
Uses that are essential because they perform important functions but for which alternative substances have been developed that have equivalent functionality and adequate performance. PFAS use can be phased out or banned.
Example: Polytetrafluoroethylene (PTFE) membranes on general-use waterproof jackets.
Uses that are essential because they are necessary for health or safety or other highly important purposes and for which alternative substances have not yet been developed. R&D is needed for alternatives.
Example: Nafion membranes for chlor-alkali production.
Ian T. Cousins, a professor of environmental science and analytical chemistry at Stockholm University, led the team of science and health researchers that authored the plan, which was published earlier this year. All are members of the Global PFAS Science Panel, a group of academics and government scientists from Europe and the US. The Tides Foundation, a philanthropic organization focused on social justice, supported the panel’s work.
Cousins tells C&EN that the proposal grew out of “The Madrid Statement,” a 2015 document warning the public and policy makers about the risks of transitioning from older environmentally persistent PFAS to newer ones, which also persist. Signed by more than 200 scientists, including Cousins and most of his coauthors on the current recommendations, the statement also calls for limiting the use of fluorochemicals and developing safer alternatives (Environ. Health Perspect. 2015, DOI: 10.1289/ehp.1509934). “The Madrid Statement” led to the 2018 “Zürich Statement,” which lays out advice to policy makers on how to decide which uses of PFAS are essential (Environ. Health Perspect. 2018, DOI: 10.1289/ehp4158).
Cousins and his colleagues modeled their 2019 proposal on an international treaty that ratcheted down the production and use of chemicals, such as chlorofluorocarbons (CFCs), that deplete Earth’s protective stratospheric ozone layer. Under that accord, the 1987 Montreal Protocol on Substances That Deplete the Ozone Layer, CFCs were quickly eliminated as propellants in most aerosol cans. Other uses of CFCs, such as in inhalers to deliver asthma drugs, were deemed essential for many years, until appropriate substitutes were developed.
Cousins’s team suggests a similar global phaseout of PFAS. The researchers propose that PFAS products be divided into three groups. One would cover what the researchers deem nonessential uses of PFAS that can be eliminated immediately because they are not necessary for health, safety, or benefit to society. A second category, substitutable uses, would involve products for which alternatives to PFAS are or can quickly become available. The third, essential uses, would cover critical uses for which appropriate substitutes are not on the horizon.
PTFE-coated dental floss lands in the first category. Other nonessential uses identified by Cousins’s team include finishes that impart water, oil, soil, and stain resistance to clothing, carpets, and paper. PFAS used for this purpose are polymeric fluorotelomer-based products, also called side-chain fluorinated polymers, according to the FluoroCouncil, a coalition of companies that manufacture fluorochemical products. Fluorotelomers are built of hydrocarbon backbones with polyfluoroalkyl side chains. Some researchers suggest that fluorinated side chains can break off the backbones and contribute significantly to PFAS in the environment, eventually breaking down into toxic perfluoroalkyl carboxylates (Environ. Sci. Technol. 2017, DOI: 10.1021/acs.est.6b04021).
Another use of PFAS that Cousins’s team suggests is not essential is in waxes that help skis glide smoothly across snow. A recently published study from researchers in Norway found PFAS from ski wax in soil, earthworms, and voles near a ski area (Environ. Sci. Technol. 2019, DOI: 10.1021/acs.est.9b02533).
PFAS ingredients in cosmetics are also not essential, the team says. The Environmental Working Group, a US-based advocacy group, has identified 17 PFAS used as ingredients in personal care products, including cosmetics. These chemicals include PTFE and perfluorodecalin. A number of cosmetic makers, including L’Oréal and the Body Shop, have pledged to remove PFAS from their products.
For the second class of PFAS, appropriate substitutes are often available now, the researchers say. PFAS for decades have been ingredients in firefighting foams used to extinguish fuel-fed blazes. But now, PFAS-free foams are on the market and used at some commercial airports, including London’s Heathrow. Another use with available substitutes is waterproof jackets for general consumers.
“It may be needed to make the alternatives more well-known and more easily available, but there is no fundamental obstacle to removing PFASs from these uses,” the team’s paper says. These alternatives might initially be more expensive than their PFAS-containing competitors, the researchers acknowledge. However, “upon increased market uptake, the costs can be expected to decrease.”
The third category the team proposes consists of PFAS uses that are essential to society and for which no established alternatives provide the required technical function and performance. An example is perfluorosulfonic membranes used for ion exchange in chlor-alkali production. Electrochemical cells that use these membranes replaced toxic mercury cells and diaphragms made from carcinogenic asbestos. Cousins and his colleagues emphasize that “essential” uses should not be considered permanent and urge the development of PFAS-free alternatives.
The concept of grouping PFAS according to societal need and substitute availability contrasts with attempts by some activists and policy makers to treat all PFAS the same. For instance, pending legislation in the US Congress would broadly govern PFAS as a class. H.R. 535, introduced by Rep. Debbie Dingell (D-MI), would mandate that the US Environmental Protection Agency designate all PFAS as hazardous substances, meaning sites contaminated with them would have to be cleaned up, with polluters footing the bill. And H.R. 2600, sponsored by Rep. Madeleine Dean (D-PA), would essentially ban the manufacture, import, and sales of all PFAS.
Not surprisingly, companies that make PFAS resist the idea of eliminating products that contain them. They emphasize that the products they make don’t present a risk to people or the environment when used as intended. And they are seeking to develop PFAS-free alternatives to their products, according to Steve Korzeniowski, a consultant to two fluorochemical makers and who has represented the FluoroCouncil at PFAS-related meetings. The FluoroCouncil is part of the American Chemistry Council, a US chemical manufacturers’ lobbying group.
Companies make PFAS-containing products because customers buy them, often at higher prices because of their performance, Korzeniowski tells C&EN. And as demand changes in the market, manufacturers are changing what they make, with some companies offering fluorinated and fluorine-free versions of products.
Makers of PFAS strive to manage their supply chain so that environmental releases of these chemicals are minimized or eliminated, Korzeniowski says. And he points out that fluoropolymers are nontoxic—they are not soluble or bioavailable.
Barbara J. Henry, principal toxicologist at W. L. Gore & Associates, says grouping PFAS together for any regulatory framework, including phaseout, is inappropriate. W. L. Gore does not manufacture fluoropolymers from scratch but transforms these plastics into material such as Gore-Tex—waterproof, breathable membranes made from expanded PTFE.
“Not only are fluoropolymers inherently low hazard, but their unsurpassed durability makes them ideal for important applications like aerospace, which requires very lightweight materials that can withstand harsh environments—and the potential impact of product failure is high, if not intolerable,” Henry tells C&EN.
But Cousins and others say it’s unreasonable for industry to continue to produce and release PFAS into the environment. All PFAS, even inert polymers like PTFE, are environmentally persistent for centuries, he points out.
“Why do we want to make products that never ever ever break down?” asks Linda Birnbaum, who recently retired as head of the National Institute of Environmental Health Sciences. Birnbaum, a toxicologist, has long studied another class of chemicals that were once commercial products and remain persistent pollutants: polychlorinated biphenyls.
Rather than making additional persistent chemicals, manufacturers need to design molecules with a built-in ability to degrade after their use, Cousins says. This idea is one of the decades-old principles of green chemistry. In addition, the manufacture of fluoropolymers requires processing aids. Salts of perfluorooctanoic acid and the next-generation alternative, Chemours’s GenX, have been or are used for this purpose. Both of these substances are toxic, and both have been found polluting drinking-water supplies near plants that manufacture or formerly manufactured fluoropolymers.
An immediate challenge facing manufacturers is the production of essential-use fluoropolymers without toxic fluorinated processing aids that can escape a facility via vents, stacks, and wastewater, Cousins says.
The concept of a PFAS phaseout based on essential uses seems to be gaining traction. Notably, the idea could end up on the agenda of the United Nations International Conference on Chemicals Management in 2020. The International Pollutants Elimination Network, or IPEN, a coalition of environmental and health groups from around the world that is working toward elimination of persistent organic pollutants, is pushing the plan in a detailed policy document it recently released in preparation for that meeting.
“The unchecked growth in production and use of PFASs needs to be turned around, and a global phase-out initiated,” that document concludes. “If emissions are not reduced, they will continue to accumulate in the environment and to be sources of exposure for us and our descendants far into the future.”