Impacts of the Degradation of 2,3,3,3-Tetrafluoropropene into Trifluoroacetic Acid from Its Application in Automobile Air Conditioners in China, the United States, and Europe

Abstract

HFO-1234yf (2,3,3,3-tetrafluoropropene) was proposed as an automobile air conditioner (MAC) refrigerant worldwide. However, its atmospheric degradation product is the highly soluble and phytotoxic trifluoroacetic acid (TFA), which persists in aquatic environments. We used a global three-dimensional chemical transport model to assess the potential environmental effects resulting from complete future conversion of the refrigerant in all MAC to HFO-1234yf in China, the United States, and Europe. The annual mean atmospheric concentrations of HFO-1234yf were 2.62, 2.20, and 2.73 pptv, and the mean deposition rates of TFA were 0.96, 0.45, and 0.52 kg km yr, in three regions. The regional TFA deposition sources mainly came from emissions within the same region. The annual TFA deposition in the North Pole region was lower than the global average and mainly originated from European emissions. A potential doubling in the future HFO-1234yf emissions in China mainly affected the local TFA depositions. The TFA concentrations in rainwater were strongly affected by the regional precipitation rates. North Africa and the Middle East, regions with scant rainfall, had extremely high TFA concentrations. The rainwater concentrations of TFA during individual rain events can exceed the level considered to be safe, indicating substantial potential regional risks from future HFO-1234yf use.

Interactive effects of changing stratospheric ozone and climate on tropospheric composition and air quality, and the consequences for human and ecosystem health

“…Inputs of TFA into the environment from future conversion of all mobile (mainly automotive) air conditioners (MACs) to HFO-1234yf in China, the USA, and Europe have been estimated using a global 3-D chemical transport model, 192 extending and confirming previous modelling for North America. 193 This modelling highlights the variability in transport globally from these sources.…”

“…The half-life of the newly introduced refrigerant, HFO-1234yf, is much shorter, of the order of 11 days, 196 thus, breakdown will occur closer to the regions of release and larger concentrations of TFA would be expected in surface waters. 192,193,197 In assessing risks from local deposition of TFA, it is important to note that TFA will form neutral salts once in contact with soil and/or surface waters. For example, from the estimates of production of TFA in China, the USA, and Europe 192 and assuming no dilution, this would be equivalent to 761, 573, and 740 ng Na salt L -1 , respectively, all of which are still several orders of magnitude less than the chronic "no observable effect concentration" (NOEC) of 10,000,000 ng L -1 for TFA-Na salt from a microcosm study.…”

“…192,193,197 In assessing risks from local deposition of TFA, it is important to note that TFA will form neutral salts once in contact with soil and/or surface waters. For example, from the estimates of production of TFA in China, the USA, and Europe 192 and assuming no dilution, this would be equivalent to 761, 573, and 740 ng Na salt L -1 , respectively, all of which are still several orders of magnitude less than the chronic "no observable effect concentration" (NOEC) of 10,000,000 ng L -1 for TFA-Na salt from a microcosm study. 198 Although the authors point out that concentrations in precipitation in arid regions would be greater, TFA salts would run-off into the ocean where they would be diluted or accumulate in endorheic bodies of water where environmental effects of other mineral salts, which are present in much greater concentrations, outweigh those of TFA salts.…”

Challenges in the analytical determination of ultra-short-chain perfluoroalkyl acids and implications for environmental and human health

“…A proposed replacement is HFO-1234yf (2,3,3,3tetrafluoropropene), which has a shorter lifetime and higher conversion rate into TFA compared with HFC-134a. A few studies have estimated that concentrations of TFA in air and wet deposition will increase in the future assuming a complete shift to HFO-1234yf [60][61][62]. Results indicate that the TFA concentration in air will increase with at least a factor of 10 in some European areas [60].…”

The concept of essential use for determining when uses of PFASs can be phased out

“…A transformation product of nearly all of the anesthetics is triuoroacetic acid (TFA or CF 3 COOH), which can arise from several metabolic or atmospheric degradation pathways 68 and has been a cause of environmental concern. [69][70][71] In summary, the addition of 1-3 uorine atoms or tri-uoromethyl groups to various pharmaceutical agents has improved their efficacy, half-lives, and bioabsorption and does not appear to pose substantial health risks to those who take them, relative to analogous non-uorinated drugs. However, their production and disposal will continue to lead to the release of PFASs into the environment unless steps are taken to eliminate environmental releases.…”