EFCTC has, through its newsletter and website(1), already commented in the past on all the points raised in recent articles “Refrigerant R1234yf again in criticism(2)” and an article about HFOs in the September issue of Accelerate magazine(3). In this article EFCTC provides important conclusions about the 4 main issues raised:
• Fire Safety and Combustion Products
• Atmospheric Concentrations
• Environmental Safety
• Water Solubility of TFA
A summary of this article as well as a Key Points brief are available on the website.
The 2018 Scientific Assessment of Ozone Depletion provides an overall perspective and concluded that “There is increased confidence that trifluoroacetic acid (TFA) produced from degradation of HFCs, HCFCs, and HFOs will not harm the environment over the next few decades. This assessment is based on the current estimates of future use of hydrofluorocarbons, HCFCs, and HFOs. It is noteworthy that HFCs and HCFCs have atmospheric lifetimes long enough to globally distribute any TFA emissions, while HFOs have atmospheric lifetimes so short that TFA emissions are deposited near the point of emission. Periodic re-evaluation is prudent, given the uncertainties in the sources and sinks of TFA and because of its persistence in the environment.” And that “The large body of published field measurements, toxicological studies, modelling studies, and environmental assessments point to a clear conclusion: The current and estimated future concentrations of TFA and its salts resulting from degradation of HCFCs, HFCs, and HFOs do not pose any known significant risk to human or ecosystem health.(4)”
EFCTC members continue to have full confidence in the use of R-1234yf as a refrigerant for mobile air-conditioning and other applications. EFCTC supports good science and thorough investigation of the properties of all fluorochemicals produced by our member companies, including HFOs. We fully endorse emission reduction strategies during use along with best practice measures that help ensure efficient capturing of HFOs during recycling operations. We should not lose sight of their good balance of safety and performance properties and their insignificant impact on the climate because they degrade rapidly in the atmosphere.
All fluorocarbon refrigerants have the potential to form dangerous combustion products and this has been known for over 50 years since the use of CFCs and HFCs, with technical advice and safety guidance provided. The advantage of fluorinated refrigerants is that they are typically much more difficult to ignite and have lower or non-flammability. In respect of R-1234yf, the EU Joint Research Centre was asked, in 2013, to provide an in-depth analysis(5) of the report elaborated by KBA (Kraftfahrt Bundesamt, German authority responsible for market surveillance and product safety for road vehicles), in order to ascertain whether the results stemming from the tests are well founded and supported by a rigorous and scientific methodology. In particular, the JRC was to clarify if, in the view of the aforementioned report, there is a reason to believe that refrigerant R1234yf may not operate in the vehicles with the appropriate level of safety, in the sense of the General Product Safety Directive (Directive 2001/95/EC) and the Framework Directive 2007/46/EC. The KBA performed a series of tests at three different levels, considering levels 1 and 2 for their assessment of possible risks within the scope of the statutory tasks as product safety authority, and level 3 tests as general risk appraisal. The level 1 and level 2 testing showed no ignition of refrigerant R1234yf and no release of hydrogen fluoride (HF) despite the very high temperatures in the engine compartment. Consequently, the results as such with the vehicles tested under the conditions as described for level 1 and level 2 testing provided no evidence of a serious risk. The refrigerant release tests under level 3 were not taken into account by the KBA as relevant input. The KBA states also that “… (only) the levels 1 and 2 were considered relevant for a risk assessment with respect to the product safety regulations, as only these can be associated with the necessary concrete probability of occurrence.” This approach taken by the KBA is supported by the JRC because it reflects JRC’s understanding of Article 2(b) of the General Product Safety Directive 2001/95/EC in which is stated “…‘safe product’ shall mean any product which, under normal or reasonably foreseeable conditions of use (…) does not present any risk or only the minimum risks compatible with the product’s use…”. Therefore, drawing of conclusions from level 3 tests, further than the ones already drawn from level 1 and level 2 tests regarding the safe operation of the refrigerant R-1234yf in MAC systems, is not appropriate, considering the definition of “safe product” in the General Product Safety Directive 2001/95/EC.
Substances having short atmospheric lifetimes (typically measured in days) are transported to some extent in the atmosphere as they breakdown. The detection of HFOs in the atmosphere, with lifetimes of about 10 to 40 days, is no different to the detection of other very short lifetime substances such as propane, isobutane, pentane (non-methane hydrocarbons NMHCs, a sub-set of non-methane volatile organic compounds NMVOCs). These hydrocarbons also have similar atmospheric lifetimes (for example 13 days for propane)(6). The much wider sources of the NMHCs typically lead to substantially higher atmospheric concentrations that can be in the ppb (parts per billion, about 1000 times greater than the HFOs) range(7), particularly in urban areas. In general terms the HFCs [and HFOs such as R-1234yf] have very low Photochemical Ozone Creation Potential (POCP) values and take no part in ground-level ozone formation (commonly known as “smog”). In contrast, the alkanes (ethane, propane and isobutane) and alkenes (ethylene and propylene) exhibit steadily increasing reactivities from ethane, which is unreactive, to propylene, which is highly reactive(8). Now that HFOs are becoming more widely used in the EU, very low atmospheric concentrations (typically below 1 ppt parts per trillion) can be detected(9). Background concentrations at end of 2017 for 3 HFOs/HCFOs are less than 0.1 ppt. To put this in context, 1 part per trillion is about the same as 1cm2 compared to the area of Paris (105.4 sq km). See EFCTC Newsletter March 2019 articlehere.
Over 200 million tonnes of trifluoroacetic acid (TFA as its salts) are present in the oceans, both coastal and deep-ocean seawater, having apparently accumulated over many million years from chemical reactions in or around sub-sea volcanic vents. More than 95% of TFA found in the oceans is naturally formed. The concentration in the oceans is small (about ~200 ng L−1 or ~ 2 x 10-10 g of TFA /g of sea water).
The effect of the atmospheric breakdown of R-1234yf to form trifluoracetic acid has been thoroughly investigated. The 2018 Environmental Effects Assessment Report(10) stated that “There is still no indication that exposure to current and projected concentrations of salts of TFA in surface waters present a risk to the health of humans and the environment. Since the risk assessment conducted in 2016, no novel studies indicating adverse long-lasting effects of TFA and its salts have been published. In fact, the reverse is true. Previous reports of contact toxicity from exposure to concentrated TFA (as a strong acid used in industry) have not indicated systemic toxicity. TFA in rain-water is millions of times more dilute than that in industrial solutions and would not cause adverse effects.” In its conclusions, the report stated that “Estimates of production of TFA in China, the USA, and Europe, from the degradation of R-1234yf from Its application in automobile air conditioners, and assuming no dilution, would be 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 an aquatic microcosms study.” and “Overall, there is no new evidence that contradicts the conclusion of our previous Assessments that exposure to current and projected concentrations of salts of TFA in surface waters present a minimal risk to the health of humans and the environment. A recent review of this topic reached a similar conclusion.(11)”
The 2018 Scientific Assessment of Ozone Depletion(12), in its conclusions, stated that “The large body of published field measurements, toxicological studies, modelling studies, and environmental assessments point to a clear conclusion: The current and estimated future concentrations of TFA and its salts resulting from degradation of HCFCs, HFCs, and HFOs do not pose any known significant risk to human or ecosystem health.”
It is well established that TFA is a ubiquitous natural component in rivers, lakes, and other surface water bodies. Amounts deposited in flowing surface water will ultimately accumulate in the oceans and salt lakes where water is lost only by evaporation. More than 95% of the salts of TFA found in the oceans are naturally produced. Because of their high solubility in water and their very small octanol-water partition coefficient, the salts of TFA do not bioconcentrate in aquatic organisms, and do not biomagnify in the food chain. Thus they present negligible risk to organisms higher on the food chain, including humans(13). For an upper range scenario of global HFC use by 2050 it was estimated that the total additional contribution of TFA to the oceans would be less than 7.5% of the TFA present at the start of the millennium. With the 2016 Kigali Amendment to the Montreal Protocol, the TFA due to global HFC use, and hence TFA formation as a breakdown product, is projected to be lower but partially offset by increased use of HFOs(14).
A recent comprehensive study investigated the quantities of trifluoroacetate (TFA) found in major rivers across Germany(15). Following this study, it had been claimed that HFO-1234yf has possible negative consequences for the production of drinking water. However, currently HFO-1234yf is at most an insignificant contributor to the quantities of TFA found. Furthermore, based on a recent study on Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe(16), the projected growth in use of R-1234yf and resulting emissions of TFA is expected to have only a small contribution to the quantities of TFA found in German rivers. This is consistent with the conclusions from the 2018 Environmental Effects Assessment(17).
1 See EFCTC LEARN ABOUT TFA For a wide range of information about Trifluoroacetic acid/acetate as a breakdown product of some HFCs and some HFOs here.
2 Springer Professional Germany source and in the DKV online news
3 Accelerate Magazine source
4 2018 Scientific Assessment of Ozone Depletion, Page ES.50 and Page 6.14
5 The JRC technical and scientific support to the research on safety aspects of the use of refrigerant R1234yf on MAC systems issued in 2014. The complete report can be accessed with by searching for Ref. Ares(2014)573175 – 04/03/2014
6 Lifetimes, direct and indirect radiative forcing, and global warming potentials of ethane (C2H6), propane (C3H8), and butane (C4H10), Øivind Hodnebrog, Stig B. Dalsøren, Gunnar Myhre, Atmospheric Science Letters, 26 February 2018, https://doi.org/10.1002/asl.804
7 See for example Sources and variability of non-methane hydrocarbons in the Eastern Mediterranean, Cecilia Arsene, A. Bougiatioti, N. Mihalopoulos, Global Nest Journal 11(3):333-340 · November 2009
8 IPCC/TEAP Special Report Safeguarding the Ozone Layer and the Global Climate System: Issues Related to Hydrofluorocarbons and Perfluorocarbons Chapter 2 page 169.
9 Continuous measurement of non-CO2 greenhouse gases on the Jungfraujoch (HALCLIM-2015-18), EMPA Materials Science and Technology, August 2018. The table on page 20 gives background atmospheric concentrations for 2017 at the Jungfraujoch station in Switzerland. These are HFO-1234yf < 0.005 ppt; HFO-1234ze(E) 0.018 ppt; and HCFO-1233zd(E) 0.045 ppt
10 Environmental Effects and Interactions of Stratospheric Ozone Depletion, UV Radiation, and Climate Change 2018 Assessment Report UN Environment Programme Section 5.1 Trifluoroacetic acid from replacements of ODS and refrigerants with large GWPs page 314
11 The recent review is the Norwegian Environment Agency, 2017, Study on Environmental and Health Effects of HFO Refrigerants, Norwegian Environment Agency Report No. No. M-917|2017, Oslo, Norway, p. 349
12 World Meteorological Organization Global Ozone Research and Monitoring Project, Report No. 58 Scientific Assessment of Ozone Depletion: 2018
13 Ecological Issues on the feasibility of managing HFCs: Focus on TFA Inter-sessional informal meeting, 12-13 June 2015, UNEP Ozone Secretariat
14 World Meteorological Organization Global Ozone Research and Monitoring Project, Report No. 58 Scientific Assessment of Ozone Depletion: 2018 Section 2.4.2
15 Marco Scheurer, Karsten Noedler, Finnian Freeling, Joachim Janda, Oliver Happel, Marcel Riegel, Uwe Müller, Florian RüdigerStorck, Michael Fleig, Frank Thomas Lange, Andrea Brunsch, Heinz-Jürgen Brauch (2017), Small, mobile, persistent: Trifluoroacetate in the water cycle – Overlooked sources, pathways, and consequences for drinking water supply, Water Research 126 (2017) pp 460-471
16 Stephan Henne, Dudley E. Shallcross, Stefan Reimann, Ping Xiao, Dominik Brunner, Simon O’Doherty, and Brigitte Buchmann, Future Emissions and Atmospheric Fate of HFC-1234yf from Mobile Air Conditioners in Europe, Environ. Sci. Technol., 2012, 46 (3), pp 1650–1658 DOI: 10.1021/es2034608.
17 Further information is available EFCTC Comment on Study on TFA in rivers in Germany and rivers as source of drinking water