Trifluoroacetic Acid: Toxicity, Sources, Sinks and Future Prospects

Trifluoroacetic acid (TFA) is a known persistent pollutant in the environment. Although several direct anthropogenic sources exist, production from the atmospheric degradation of fluorocarbons such as some hydrofluorocarbons (HFCs) has been a known source for some time. The current transition from HFCs to HFOs (hydrofluoroolefins) is beneficial from a global warming viewpoint, because HFOs are much shorter-lived and pose a much smaller threat to warming, but the fraction of HFO conversion to TFA is higher than for the corresponding HFCs and the region over which the TFA is produced is close to the source. Therefore, it is timely to review the role of TFA in the Earth’s environment. This review considers its toxicity, sources and removal processes, measurements in a variety of environments and future prospects. New global model integrations quantify the impacts on TFA levels of uncertainties in the Henry’s Law constant for TFA and the range of gas-phase kinetic parameters determined for the reaction of OH radicals with a representative HFO (HFO-1234yf). Model runs suggest that TFA surface concentrations vary by up to 10% based on Henry’s Law data, but could be up to 25% smaller than previously modelled values depending on the kinetic analysis adopted. Therefore, future estimates of TFA surface concentrations based on HFO removal re-quire updating and the kinetic analysis of TFA production warrants further investigation. The toxicity of TFA appears to be low but further studies of a much wider range of animal and plant types are required.