Produced in the atmosphere from HFO-1234yf and other f-gases, trifluoroacetic acid is an omnipresent PFAS with potentially irreversible disruptive effects, the study says.
A new study makes the case that trifluoroacetic acid (TFA), an atmospheric byproduct of HFO1234yf and other f-gases, meets the criteria of a “planetary boundary threat” because of increasing planetary-scale exposure, where “potential irreversible disruptive impacts on vital earth system processes could occur.”
The study, “The Global Threat from the Irreversible Accumulation of Trifluoroacetic Acid (TFA),” was published October 30 in the journal Environmental Science & Technology. Its authors are Hans Peter H. Arp and Andrea Gredelj of the Norwegian Geotechnical Institute; Juliane Glüge and Martin Scheringer of the Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich; and Ian Cousins of the Department of Environmental Science, Stockholm University. The study received funding from ZeroPM and ARAGORN EU.
The TFA study reviewed 43 studies from the late 1990s to the 2020s that reported on TFA concentrations, concluding that “collectively, these data indicate that TFA exposure is widespread and is increasing.”
It found that none of the current studies “considered actual long-term exposure to TFA, which would be more relevant given its ubiquitous and increasing presence over long time scales.” Even so, “there are more than sufficient data to conclude that TFA poses a risk to humans and the environment.”
The rational response to this global threat, the TFA study said, “is to act swiftly before irreversible impacts are manifested at a global scale to humans and the environment. Transitioning away from TFA and its precursors is the most effective way of safeguarding future generations from this planetary boundary threat.”
TFA and its f-gas precursors are considered PFAS (per-and polyfluoroalkyl substances) by the EU and scientists worldwide because they have at least one fully fluorinated carbon atom. PFAS, also known as “forever chemicals” for their persistence in nature, encompass more than 14,000 synthetic substances that are used in many common consumer and industrial products. PFAS which contain eight carbon atoms, such as PFOA and PFOS, have been linked to serious health problems, including kidney and testicular cancer.
Exposure to TFA, an ultrashort-chain PFAS with two carbon atoms, has not been conclusively associated with health effects, but the German government this year proposed to the EU linking TFA to reproductive toxicity based on evidence of embryo-fetal developmental toxicity in rabbits, and TFA has been connected to liver dysfunction in rats. Germany has also proposed categorizing TFA in the EU as persistent, mobile and toxic (PMT) and very persistent and very mobile (vPvM).
Meanwhile, the European Chemicals Agency (ECHA), an EU body, is considering a proposal to regulate PFAS as a category, including f-gases and TFA, under REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), the EU’s chemicals regulation. Also in the EU, a new organization, the Coalition for PFAS Free Cooling & Heating, has been launched, with ATMOsphere, publisher of NaturalRefrigerants.com, as a founding member. The organization will be dedicated to promoting natural refrigerants as alternatives to harmful PFAS in cooling and heating systems and supporting an ambitious European PFAS regulation.
While several f-gases degrade to TFA in the atmosphere, HFO-1234yf, used globally in millions of car air-conditioning systems and in commercial refrigerant blends, undergoes 100% transformation to TFA within a few weeks; the TFA then comes down to Earth in rainfall. The uptake of HFOs “could cause emissions of TFA to increase by orders of magnitude in the coming years,” said the TFA study. It pointed to several sources in addition to f-gases that generate TFA as a byproduct, including pesticides, pharmaceuticals, fluoropolymers and other PFAS, as well as to the direct release of industrially produced TFA and TFA emitted from wastewater treatment plants and landfills.
As a consequence, TFA has been proliferating throughout the environment in rain, surface water, soil, human blood serum, plants, plant-based foods and drinking water. In fact, noted the study, TFA concentrations are “orders of magnitude higher” than those of other PFAS while ongoing emission concentrations are “increasing irreversibly.”
“What remains less clear are the thresholds where irreversible effects on local or global scales occur,” the TFA study said. “There are indications from mammalian toxicity studies that TFA is toxic to reproduction and that it exhibits liver toxicity. {But] ecotoxicity data are scarce, with most data being for aquatic systems; fewer data are available for terrestrial plants, where TFA bioaccumulates most readily.”
“Transitioning away from TFA and its precursors is the most effective way of safeguarding future generations from this planetary boundary threat.”
“The Global Threat from the Irreversible Accumulation of Trifluoroacetic Acid (TFA),” Environmental Science and Technology
In a LinkedIn post, study co-author Arp wrote, “#TFA is now the most abundant #PFAS in drinking water, the most abundant #PFAS in your blood, the most abundant #PFAS in your juice, your wine, your tea, your beer, the trees outside your window, the snow falling down in the Arctic, the groundwater wells, the soils.”
“Some have said, so what? It’s not toxic,” Arp continued, “which is another way of saying, pump up the TFA in my blood, plants and water for the rest of my life, all good.” He added, “We are ignorant of where the biggest impacts of TFA on the global scale will be realized, but we know that when they are, they are irreversible.”
The American Chemistry Council and the European Fluorocarbons Technical Committee (EFCTC), which represent HFO producers, both declined to comment on the study.
The chemical industry addressed the environmental 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. 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.
Meeting three conditions
”TFA study co-author Cousins contributed to a 2013 study, “Confronting Unknown Planetary Boundary Threats from Chemical Pollution,” which identified three conditions that must be simultaneously met for chemical pollution to pose a planetary boundary threat. In the TFA study, the authors contend that TFA meets these conditions:
- Condition 1: The pollution has a disruptive effect on a vital earth system process of which we are ignorant.
- Condition 2: The disruptive effect is not discovered until the associated impacts are, or inevitably will be, manifested at a global scale.
- Condition 3: The impacts are poorly reversible because the level of pollution in the global environment cannot be readily reduced.
Condition 1 is met based on “the many [TFA] thresholds that could be exceeded of which we are ignorant,” the study said. This includes surface water concentrations that may exceed the predicted no-effect concentration (PNEC) for algae of 560mcg/L set by the ECHA; soil concentrations that may exceed the lowest established no observed effect concentration (NOEC) for crop plants of 0.83mg/kg of soil, according to REACH; and indications of human toxicity that have led to precautionary thresholds in drinking water in the Netherlands (2.2mcg/L), Denmark (9mcg/L) and Germany (health guideline of 60mcg/L and advisory level of 10mcg/L).
Although TFA does not currently have health advisories or regulatory limits that are as well-established as those for other acid-based PFAS like PFOA, “it is likely that new advisories/limits will be introduced in the coming years when more research on the impacts of TFA emerges,” the study said.
Condition 2 is fulfilled as “TFA is already present globally in all environmental media, such as its ongoing bioaccumulation in vascular plants, the accumulation in arctic regions, its ubiquity in groundwater, and the global occurrence of industrial sites that are TFA hotspots where impacts are most likely; therefore, when impacts are discovered, they would be global.” Condition 3 is satisfied “due to TFA’s extreme persistence and mobility coupled with emissions from multiple sources.”
The TFA study cited many other studies and reports in defense of its description of TFA as a planetary boundary threat:
- Many findings of TFA levels in drinking water have exceeded the EU’s “total PFAS” (including TFA) limit of 0.5mcg/L, set to begin in 2026. Moreover, the most effective way to remove TFA from water – reverse osmosis (RO) – is expensive, requires a substantial amount of energy and typically results in 50% water loss.
- Because of growing water and soil concentrations, TFA has been accumulating in plants like conifer needles, maize, leaves of various tree species and some wetland species. Consequently, high concentrations of TFA in plant-based foods and plant-based beverages such as juice, beer and tea have been reported, indicating that the ingestion of plant-based foods and beverages could be a substantial route for human (and animal) exposure.
- In another study the concentrations of TFA in the blood serum of nonoccupationally exposed citizens in Indiana (U.S.) households are similar to the concentrations of bioaccumulative long-chain PFAS measured in the serum of occupationally exposed workers in a University of North Carolina study.
- Recently investigations by German researchers have shown the effects of TFA on soil pH, microbial respiration, bacterial abundance and litter (dead leaves) decomposition; litter decomposition – a process that adds nutrients to the soil – is affected at concentrations similar to current TFA concentrations in soil at contamination hotspots (0.0013–2.4 mg/kgdw).
- U.S. water researchers showed the incorporation of TFA into cells by microbial communities in freshwater surface sediments after also demonstrating TFA incorporation in biomolecules such as proteins in aquatic organisms. TFA concentrations overlap with those currently observed in waters worldwide, ranging from 2.2 to 43μg/L, and resulted in significant cell incorporation of TFA.
The TFA study also challenged the conclusions of some TFA investigations:
- Studies of chronic exposure to TFA are still relatively scarce, with chronic data from standardized tests being limited in time of exposure to, for example, 35 days in fish, 21 days in Daphnia, 90 days in rats and 36 days in crop plants. These are insufficient in their extrapolation to potential impacts from lifetime exposure to TFA.
- Earlier studies have regarded TFA as less hazardous and bioaccumulative than longer-chain PFAS, but these reports don’t consider TFA’s ubiquitous accumulation in the environment, in particular its observed accumulation in water resources and bioaccumulation in various plants, including crops.
- Some recent studies have concluded the risk of TFA to humans and the environment is negligible based on a projected concentration of TFA in the ocean and current levels in blood serum. However, the TFA study rejected this conclusion because it ignores terrestrial environments, assumes that the lowest measured environmental effect levels are known despite the lack of long-term chronic exposure data for other species and does not consider diverse human exposure pathways in diet and potential unknown adverse effects such as on embryo development.
Action urged
With the projected exponential increase in TFA concentrations in the environment, food and in humans, “the question is not if TFA can exceed a planetary boundary, but which irreversible health or Earth system impacts would be first observed at a planetary scale, and where thresholds of TFA emissions should be set to limit the severity of such impacts,” the study said.
The study calls for stakeholders to immediately start discussing “policy, industry, and innovation actions toward the phase-out of high-volume substances that lead to increasing TFA accumulation” such as HFOs like HFO-1234yf and pesticides such as flufenacet. Other pharmaceuticals, veterinary products and industrial chemicals that release TFA via transformation processes should also be considered for phase out or substitutions, the study said.
“[TFA] can be put on the list of accumulating persistent substances we know are [causing] or can cause planetary harm, like greenhouse gases, nutrients causing eutrophication, and ozone- depleting substances,” wrote Arp on LinkedIn.
