A new study funded by the German government has found trifluoroacetate (TFA), a degradation product of certain HFCs and HFOs, “widespread and dominant” in 46 water samples collected from 13 different sources of German drinking water.
The study – “Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated” – was published May 4 in Environmental Science & Technology. Its authors are Isabelle J. Neuwald, Daniel Hübner, Hanna L. Wiegand, Vassil Valkov, Ulrich Borchers, Karsten Nödler, Marco Scheurer, Sarah E. Hale, Hans Peter H. Arp, and Daniel Zahn.
Funded by Germany’s Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, the study looked for the presence of short chain and ultra-short-chain PFAS (known as “forever chemicals” for the durability in nature); TFA is considered an ultra-short-chain PFAS, according to the Organisation for Economic Co-operation and Development (OECD). The samples were taken between October 27 and November 4, 2020.
In its acid form (trifluoroacetic acid), TFA is produced in the atmosphere by the 100% breakdown of HFO-1234yf, and is carried in rainfall to the earth, where it is found in acetate form. Between 7% and 20% of HFC-134a breaks down into TFA in the atmosphere.
Short-chain and ultra-short-chain PFASs “generally fulfill” the proposed criteria for persistent, mobile, and toxic (PMT) or very persistent and very mobile (vPvM) substances, established by the German Environment Agency (UBA). Consequently, ultra-short-chain PFASs “represent a major challenge for drinking water production and show that regulation in the form of preventive measures is required to manage them,” the study says.
TFA was the most dominant PFAS found in the study, accounting for more than 90% of the total concentration of PFAS analyzed in all samples, with a maximum and median concentration of 12.4 and 0.9 μg/L, respectively. “From the data presented herein, it is evident that short-chain PFASs and especially the ultra-short-chain PFASs TFA, TFMS [trifluoromethanesulfonate], and PFPrA [perfluoropropanoate] are widespread and dominant in these samples from drinking water sources,” the study says.
The TFA results are “in line with previous monitoring programs in German surface waters,” the study says. A 2020 study done on behalf of the German Environment Agency (UBA) across eight locations in Germany measured the concentration of TFA in rainwater. From February 2018 to January 2019, an average of 0.330µg/L of TFA was found in 566mm (22.3in) of precipitation; from February 2019 to January 2020, an average of 0.398µg/L was found in 694mm (27.3in). Compared to earlier studies done in 1995-1996 and 1996-1997, the amount of TFA has increased by three-to-five times.
In Germany, TFA has a “drinking water health guidance value of 60 μg/L” and “a target value as a plant protection agent metabolite” (precautionary value) of 10 μg/L, the study says.
Denmark has also been studying the presence of TFA in water supplies. In 2021, the Danish Environmental Protection Agency reported finding TFA in 219 out of 247 groundwater wells, as well as in some drinking water supplies. In the vast majority of groundwater wells, the concentration of TFA is lower than 1 µg/L.
Canadian researchers have also studied the presence of TFA in the environment. Other recent studies of current and projected TFA levels were reviewed at the ATMOsphere Europe conference last year.
In response to concerns about the growth of HFO and TFA levels in the environment, five European countries announced last year their intention to submit a joint proposal to restrict per- and polyfluorinated alkyl substances (PFAS), including some HFC and HFO refrigerants, to the European Chemicals Agency (ECHA) under the REACH regulation by July 2022 (which has been postponed to January 2023).
Potential health effects
The ultra-short-chain PFAS, which were the most prevalent PFASs found in the drinking water sources are also the ones that are the most difficult to remove during drinking water production, the study says. “This raises questions both about the costs of removing these substances and the potential health effects these chemicals might cause.”
The study acknowledged that there is currently little to no data about long-term exposure of ultra-short chain PFAS like TFA. However, “PFASs will remain in the environment for decades once released due to their persistent nature” and “remediation is either unfeasible or exceedingly expensive if adverse effects from these PFASs occur.”
The study suggested that the results can be used to “better account for ultra-short-chain PFASs in fresh water and drinking water sources and to support monitoring campaigns, policy development, and risk assessment of these problematic substances.”
The study did not attempt to identify the source of the TFA found in water samples. It noted that TFA can be introduced into the water cycle through industrial processes and as a transformation product of pharmaceutical and agricultural products, among others. But it also observed that TFA is also a “transformation product of hydrofluorocarbon refrigerants in the atmosphere and may reach the aqueous environment via atmospheric deposition.”
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.”
“PFASs will remain in the environment for decades once released due to their persistent nature” and “remediation is either unfeasible or exceedingly expensive if adverse effects from these PFASs occur.”Research study “Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated”
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.