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Global modelling study of TFA deposition from HFOs and HCFOs

16.01.2026

The formation and distribution and deposition of atmospheric TFA from the gas phase oxidation of fifteen HFOs and HCFOs has been reported [1]. This global atmospheric modelling studies the release and oxidation of these HFOs and HCFOs, using hypothetical scenarios with annual emissions of 1, 10 and 100 Gg (1000; 10,000; and 100,000 tonnes/year) for each of the HFOs with results for individual HFOs reported separately and compared. The scenarios use lower and upper limit TFA yields (explanatory note -these are similar to the central estimates and theoretical upper limits reported by EEAP [2]).  The fifteen HFOs and HCFOs have a range of atmospheric lifetimes from 6 days to about 100 days and the authors state that their present work quantifies the spatial distribution of TFA deposition following release of these substances, with the distribution being influenced by their atmospheric lifetimes.  The longer lived HFOs and HCFOs (including HFO-1336mzz(E), and HCFO-1233zd(E)) travel considerable distances, resulting in more geographically widespread TFA formation with lower concentrations. In contrast, the shorter lived HFOs (including HFO-1234yf and HCFO-1233xf) break down more rapidly closer to their emission sources, resulting in more concentrated (elevated) TFA surface levels. The distribution of TFA emissions from the use and emissions of HFO-1234yf has already been widely reported [3, 4, 5, 6] and the authors note that their results for HFO-1234yf are consistent with these previous studies.

The fifteen HFOs and HCFOs include:

  • Widely used as refrigerants, foam blowing agents and solvents: HFO-1234yf, HFO-1234ze(E), HFO-1336mzz(E), HFO-1336mzz(Z) and HCFO-1233zd(E), and also HCFO-1233zd(Z),
  • Used as feedstocks, intermediates or monomers: HCFO-1233xf used as a feedstock to make HFO 1234yf, PFO-1216 (hexafluoropropene) used as a monomer to make fluoropolymers and HFO-1243zf registered under REACH as an intermediate [7]. Any emissions relate to their production and use as a feedstock and do not equal the volume produced. The MCTOC most likely emission factor for modern-day, regulated manufacturing from production, supply chain, and use of feedstock is 3.6 weight % [8]
  • Substances that have limited or no application due to their toxicity: HFO-1225ye(E) and HFO-1225ye(Z) are not used as refrigerants or foam blowing agents.  HFO-1225ye(Z) exhibited toxic effects [9] upon longer exposures at the relatively low levels of 500 to 1,000 ppm, which precludes its use in these applications. Similar toxic effects would be expected for HFO-1225ye(E).
  • Limited or no applications: HFO-1234ze(Z), HFO-1318my(Z), HFO-1318my(E) and HFO-1438ezy(E)

Selection of the HFO emission inventory. The authors concluded that 10 Gg (10,000 tonnes) was an appropriate global emission scenario for each substance, for the purposes of the study, with a reported emission flux for HFO-1234yf of 4000 tonnes from Europe. This is based on a comparison of modelled HFO mixing ratios with measurement data from AGAGE (Advanced Global Atmospheric Gases Experiment, Jan–Dec 2024) stations which shows that the modelled HFO-1234yf, HFO-1234ze(E) and HCFO-1233zd(E) mixing ratios are consistent with measurements at Mace Head (Ireland), Tacolneston (UK)  and Jungfraujoch (Switzerland) when considering the 10 Gg/year HFO emission scenario. It is worth noting that a separate pre-print [10] reports emissions for NW Europe (Belgium, Germany, France, UK, Ireland, Luxembourg and the Netherlands) as 1500 tonnes, 960 tonnes and 1000 tonnes/year by 2023, for HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E), respectively. For HFO-1234yf emissions, using an extrapolation based on the number of passenger cars (in 2023, NW Europe 139 million vs 296 million in the EU27+) from the NW Europe countries to the EU27+ (27 EU countries plus the UK, Switzerland, and Norway), results in 3200 tonnes for 2023 for EU27+. Population based extrapolations to EU27+ for HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E) result in emissions of 3100 tonnes, 2000 tonnes and 2170 tonnes in 2023 respectively.

Deposition of TFA within the emission regions. In addition to detailed global deposition maps for each of the HFOs and HCFOs, the paper reports the percentages of TFA deposited within the regions that are the source of emissions and also deposited over the oceans. For HFO-1234yf, 49% is deposited within the emission region, with reduced percentages for the other main HFOs and HCFOs, linked to their longer atmospheric lifetimes.

Deposition of TFA over the oceans. A variable amount of TFA deposition from individual HFOs are found over land (with a range of 34% to 50%) and the ocean (50 to 66%). For HFO-1234yf, 55% of generated TFA is deposited over the oceans, with increased percentages for the other main HFOs and HCFOs, linked to their longer atmospheric lifetimes.

References

[1] Khan, M.A.H., Mendes, D. C., Holland, R. E. T., Garavagno, M. d. l. A. Orr-Ewing, A. J. Stanley, K. M., et al., Global modeling of trifluoroacetic acid surface concentration and deposition from the gas-phase oxidation of a wide range of precursor hydrofluoroolefins, Environ. Sci.: Atmos., 2026, Advance Article, https://doi.org/10.1039/D5EA00108K

[2] UNEP 2022 Assessment Report of the Environmental Effects Assessment Panel (EEAP), available at  Environmental Effects Assessment Panel (EEAP) | Ozone Secretariat

[3] J. Kazil, S. McKeen, S.-W. Kim, R. Ahmadov, G. A. Grell, R. K. Talukdar and A. R. Ravishankara, Deposition and rainwater concentrations of trifluoroacetic acid in the United States from the use of HFO-1234yf, J. Geophys. Res. Atmos., 2014, 119(14), 59–14079.

[4] D. J. Luecken, R. L. Waterland, S. Papasavva, K. N. Taddonio, W. T. Hutzell, J. P. Rugh and S. O. Andersen, Ozone and TFA impacts in North America from degradation of 2,3,3,3-tetrafluoropropene (HFO- 1234yf), a potential greenhouse gas replacement, Environ. Sci. Technol., 2010, 44, 343–348.

[5] S. Henne, D. E. Shallcross, S. Reimann, P. Xiao, D. Brunner, S. O'Doherty and B. Buchmann, Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe, Environ. Sci. Tecnol., 2012, 46, 1650–1658.

[6] Z. Wang, Y. Wang, J. Li, S. Henne, B. Zhang, J. Hu and J. Zhang, 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, Environ. Sci. Technol., 2018, 52, 2819–2826.

[7] 3,3,3-trifluoropropene 100.010.580 | Overview - ECHA CHEM

[8] TEAP (2024). Technology and Economic Assessment Panel Progress Report, Volume 1, Table 5-9. Available at Technology and Economic Assessment Panel (TEAP) | Ozone Secretariat

[9] Schuster, P. X., Biotransformation of Trans-1,1,1,3-tetrafluoropropene, 2,3,3,3-Tetrafluoropropene and 1,2,3,3,3-Pentafluoropropene (Bayerischen Julius-Maximilians-Universita¨t Wurzburg, 2009).

[10] M. K. Vollmer, J. R. Pitt, D. Young, S. Henne, B. Mitrevski, J. Mühle et al., Global Observations and European emissions of the halogenated olefins HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E) from the AGAGE (Advanced Global Atmospheric Gases Experiment) network. Preprint egusphere-2025-4824, https://doi.org/10.5194/egusphere-2025-4824