Trifluoroacetic acid (TFA), a persistent chemical classified as potentially toxic, has seen its global environmental presence more than triple over the past two decades. This surge is largely attributed to refrigerants now employed in systems designed to mitigate ozone depletion.
The atmospheric fallout of TFA, carried by wind and rain, dramatically increased from approximately 6,800 tonnes annually in the year 2000 to 21,800 tonnes by 2022. While current levels remain below recognized safe thresholds, the long-term effects of TFA on human health have not been extensively studied. Moreover, its environmental accumulation is projected to accelerate significantly.
Experimental studies have indicated concerning impacts, with one trial revealing that TFA exposure caused eye deformities in a majority of rabbit fetuses. The European Union has already identified it as harmful to aquatic life and is presently evaluating whether to designate it as toxic for human reproduction. Lucy Hart, a researcher at Lancaster University in the UK who spearheaded new investigations into TFA, expressed apprehension. “It is alarming that we are releasing substantial quantities of a chemical into the environment with a severe lack of understanding regarding its consequences, and it is essentially irreversible,” she commented.
The pervasive nature of TFA means human and animal exposure through soil and surface water is inevitable. Eventually, this contamination will reach the oceans, where it may become trapped in sediment layers over decades or centuries.
The Genesis of Increased TFA Concentrations
Historically, chlorofluorocarbons (CFCs) were widely used in appliances like refrigerators, aerosol sprays, and fire extinguishers. Their prevalence ceased in 1987 following the discovery of their detrimental impact on Earth’s protective ozone layer. These were largely superseded by hydrofluorocarbons (HFCs). Within the atmosphere, HFCs react with hydroxyl radicals, leading to the formation of various chemical components, including TFA.
Although HFCs are currently undergoing a phase-out process, their replacements are frequently hydrofluoroolefins (HFOs). HFOs are known to degrade into TFA at a considerably higher rate. For instance, HFO-1234yf, a compound now common in the air conditioning systems of millions of vehicles, generates TFA at a rate ten times greater than the HFCs it is progressively replacing. Beyond refrigerants, TFA also originates from sources such as pesticides, pharmaceuticals, and industrial chemical processes.
Tracing TFA’s Accumulation Through Research
Ice core samples extracted from northern Canada and Svalbard provide evidence of rising TFA concentrations dating back to the 1970s. By analyzing atmospheric measurements of nine CFC replacement gases over an extended period, Hart and her team developed a model to estimate the global production and deposition rates of TFA. Their calculations revealed a 3.5-fold increase in TFA levels worldwide.
Projections indicate that this rate could potentially double by the year 2050, based solely on the continued presence of HFCs, which can persist in the atmosphere for many years. Additional research suggests that HFO-1234yf could lead to a more than twenty-fold increase in TFA production by the same year.
Considering Sustainable Alternatives
While the global community cannot revert to using CFCs and should continue transitioning away from HFCs due to their significant contribution to global warming, Lucy Carpenter of the University of York, UK, emphasizes the need for further scrutiny of the chemicals replacing them. She points to ammonia as a viable cooling agent, already in use for numerous food storage facilities and industrial operations, with potential applications in domestic refrigerators and air conditioning systems. Carbon dioxide is also identified as a natural refrigerant alternative.
“We must seriously evaluate whether superior alternatives to HFO-1234yf exist,” Carpenter stated. “TFA levels have risen and are expected to continue increasing. It is now detected in a wide array of food products where it was previously absent. It is ubiquitous.”
A study conducted in 2020 identified elevated TFA concentrations in the blood of 90 percent of individuals in China. This region is considered a TFA hotspot due to industrial pollution and a prevalent warm, humid climate.
The European Union, currently formulating proposals for a ban on persistent chemicals, had previously anticipated that TFA concentrations in freshwater would eventually reach toxic levels. However, this prediction has faced criticism due to the engagement of a consultancy with known ties to chemical manufacturers, which has actively disputed the projected increase in TFA.
The latest findings serve as an impetus for comprehensive research into both HFOs and their potential substitutes. Hart believes this is crucial for nations to break the cycle of adopting chemicals that yield unforeseen consequences. Unlike HFCs, HFOs break down relatively quickly, offering greater control over their environmental impact. “If we cease their emission, TFA production will stop very rapidly,” she concluded.