The definition of PFAS (per- and polyfluoroalkyl substances) used by the U.S. Environmental Protection Agency (EPA) should be broadened to include chemicals such as certain HFC and HFO refrigerants, as well as refrigerant byproduct trifluoroacetic acid (TFA), according to a scientist from the Green Science Policy Institute (GSPI).

The scientist, Lydia Jahl, Science and Policy Associate for GSPI, presented this view via Zoom at a session on the impact of refrigerants on health, safety and climate at the ATMOsphere (ATMO) America Summit 2022. ATMO America, held June 7-8 in Alexandria, Virginia, was organized by ATMOsphere, publisher of R744.com.

The PFAS category comprises thousands of “forever chemicals” that are toxic, bioaccumulate in humans, animals and plants, and are extremely durable in the environment due to the extremely strong carbon-fluorine chemical bond. They have been employed in hundreds of consumer products, including non-stick cookware, stain repellent, food packaging cosmetics and clothing. The ubiquity of PFAS has led to their being found in drinking water, among other places in the environment.

Two PFAS chemicals – PFOA, used in Teflon non-stick pans, and PFOS, an ingredient in 3M’s Scotchgard stain repellent – were phased out in the U.S. by the EPA after the discovery of their health hazards, which include  cancer, reproductive problems and endocrine disruption.

Because of the difficulty of regulating thousands of individual PFAS chemicals, scientists have urged that PFAS be addressed as a class. However, two differing definitions of this class have emerged.

A definition published last year by the OECD (Organization for Economic Co-operation and Development) describes PFAS as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom. This definition is accepted by “leading PFAS scientists around the world,” said Jahl. It is also used by the National Defense Authorization Act (NDAA) and several U.S. states.

In Europe, five counties are expected to ask theEuropean Chemicals Agency (ECHA) in January to regulate PFAS under the OECD definition, including some f-gases and TFA. The f-gas industry in Europe has pushed back against the classification of HFCs and HFOs as PFAS. “HFCs, HFOs and HCFOs are a distinct subset and due to their properties are not commonly regarded as PFAS,” says the European Fluorocarbons Technical Committee (EFCTC) on its website.

By contrast with the OECD definition, the EPA, through its Office of Chemical Safety and Pollution Prevention (OCSPP) defines PFAS more narrowly, saying it contains at least two adjacent carbon atoms, where one carbon is fully fluorinated and the other is at least partially fluorinated.

The OECD’s definition of PFAS includes certain f-gases like R134a (an HFC) and R1234yf (an HFO), as well as TFA, which is formed in the atmosphere by the breakdown of 100% of R1234yf and up to 20% of R134a. The EPA definition excludes f-gases and TFA, and many other harmful chemicals.

Because TFA and f-gases may have only one fluorinated carbon atom, they are called ultra-short-chain PFAS under the OECD definition. The best-known PFAS, which have been subjected to the most regulation, are long-chain PFAS such as PFOA and PFOS, which have eight carbon atoms. However, short-chain and ultra-short-chain PFAS share many of the characteristics of long-chain PFAS, and are even harder to remove from drinking water than long-chain PFAS.

“HFOs and TFA should be considered PFAS for their shared chemical structure, persistence and potential for harm,” said Jahl. “There’s no indication that ultra-short-chain [PFAS] molecules are safe. EPA’s incomplete PFAS definition leaves room for harm.”

Jahl cited Linda Birnbaum, formerly the head of the National Institute for Environmental Health Sciences, who told The Guardian that the definition the EPA’s toxics office uses is “ a lot more like industry’s” rather than like the definition used by the international scientific community. “This highlights the importance of listening to the scientists who are actually studying these chemicals in depth,” Jahl added.

Jahl acknowledged that more toxicology data is needed “to be 100% certain” of TFA’s potential effect on human health in water supplies and other places where it is collecting. “But we need that toxicity data before it would be wise to continue using TFA and products that results in TFA formation.”

This is especially true, Jahl added, given the availability of natural refrigerants as “safer alternatives.”

The chemical industry has addressed the deposition of TFA in an October 2021 study funded by the Global Forum for Advanced Climate Technologies (globalFACT), which represents f-gas producers Chemours, Honeywell, Arkema and Koura (and equipment manufacturer Daikin). The study concluded that “with the current knowledge of the effects of TFA on humans and ecosystems, the projected emissions through 2040 would not be detrimental.”

But the study also acknowledged that “the major uncertainty in the knowledge of the TFA concentrations and their spatial distributions is due to uncertainties in the future projected emissions.”

Neither Chemours or Honeywell responded to a request for comment for this article on the definition of PFAS.

“HFOs and TFA should be considered PFAS for their shared chemical structure, persistence and potential for harm.”

The EPA’s more restrictive definition of PFAS has prompted criticism from a number of quarters in the past year. Last September, scientists from GSPI and several other groups (including the Environmental Working Group and the Natural Resources Defense Council) sent a letter to EPA Administrator Michael Regan urging the agency to use the OECD’s definition of PFAS, which they called “scientifically sound and consistent with definitions that have been included in federal and state laws regulating PFAS.”

The letter also noted that the EPA’s definition excluded many HFC and HFO refrigerants as well as TFA, which “poses risk to human and ecological receptors.” The scientists pointed out that TFA has been recognized as a PFAS by the California Department of Toxic Substance Control, among others.

U.S. legislators have also weighed in. Last November, Representatives Deborah Ross (Democrat from North Carolina) and Nancy Mace (Republican from South Carolina) introduced the PFAS Definition Improvement Act (HR 5987), which would define PFAS as the OECD does.

More recently, in a suit against the EPA in April, Public Employees for Environmental Responsibility (PEER), a Washington, D.C.-based NGO, alleged that the agency was “withholding documents explaining why it has adopted an exceedingly limited definition of [PFAS].”

EPA subsequently released more than 2,500 pages of documents, but on June 10 PEER said in a statement that it found “no scientific basis” for the EPA’s working definition of PFAS, and “no reasons given for excluding thousands of chemicals included in State definitions.” PEER added that it will challenge in court redactions in the EPA’s documents that “may mask the scientific basis” for its PFAS definition.

The EPA did not respond to a request for comment for this article on the reasons for its PFAS definition.

In her presentation, Jahl cited a number of studies finding growing amounts of TFA in the environment, which she attributed to “the broad use of HFCs and HFOs that react in the atmosphere to cause TFA formation.”

While a significant generator of TFA, f-gases are not its only source, noted David Behringer, Project Manager for Öko-Recherche, a German environmental consultancy, who participated in the impact of refrigerants session with Jahl. TFA is emitted directly from its manufacturing process (for lab use, for example) and is the degradation product of many herbicides and pesticides. “No one knows exactly how those sources contribute to the TFA in the environment.”

However, added Behringer, the continued use of HFO-1234yf in mobile air-conditioning “could well result in a situation where in the future the RAC [refrigeration and air conditioning] sector is the main contributor [of TFA].”

Examples of the growth of TFA in the environment include a 17-fold increase in China groundwater, a 10-fold increase in Canadian Arctic ice, and an increase in plant material in Germany. The growth in the Arctic is particularly notable since “there is no direct use of HFOs or TFA in the Arctic,” she said.

Other studies she mentioned found TFA in 89% and 96% of drinking water samples in Denmark and Germany, respectively, as well as “in high concentrations” in more than 90% of blood serum samples in China. Another study, she noted, found TFA in beer and tea at concentrations of 6ppb (parts per billion) and 2ppb, respectively.

The German Environment Agency (UBA) has set a “health orientation value” of 60mg/L (60ppb) and a precautionary measures value of 10mg/L (10ppb) for drinking water, noted Behringer. In his presentation, he described a study he participated in that found TFA concentrations in rainfall across Germany had increased three to five times compared to studies done more than 20 years earlier.

Last week, the EPA announced that lifetime exposure to PFOA and PFOS, at the extremely low levels of 0.004 and 0.02ppt (parts per trillion), respectively in drinking water “can compromise the immune and cardiovascular systems and are linked to decreased birth weights,” according to an article in the Washington Post. EPA’s previous health advisory for these chemicals in 2016 were set at 70ppt.

Want to find out more, or have something to say about this story? Join the ATMO Connect network to meet and engage with like-minded stakeholders in the clean cooling and natural refrigerant arena.

R744.com is an independent marketplace for ammonia HVAC&R products and services, and a trusted source for the latest ammonia news from around the world.