Increasingly Often TFA on Your Plate

‘High concentrations of PFAS in European wines’ – so reported the media at the end of April. A European coalition of environmental organisations (Pesticide Action Network Europe) had 49 wines analysed for the presence of trifluoroacetic acid (TFA), also known as the smallest PFAS. The report shows that in 39 recently produced wines from ten countries, peak values of well over 300 micrograms per litre are sometimes recorded. For comparison: the recently established guideline values for drinking water in the Netherlands (2.2 micrograms per litre) and Flanders (15.6 micrograms) are considerably lower – although most people naturally drink far more water than wine.

The analytical laboratory also sampled ten bottles of older wines. These reveal that between 1988 and 2010, TFA concentrations were lower: between 13 and 21 micrograms per litre. From 2015 onwards, the average TFA concentration climbs towards 120 micrograms. At the beginning of June, a follow-up study by the same coalition was published on TFA in grain products, such as pasta, bread and biscuits. Here too, a significant rise is visible compared with measurements taken eight years ago.

Pesticides

According to the Flemish organisation Bond Beter Leefmilieu, one of the participating organisations in the study, there is a clear link with pesticide use. Lower average TFA concentrations were measured in organic wines, and the same holds true for residues of other pesticides. Nevertheless, the dividing line between organic and conventional wines where TFA is concerned is far from clear-cut. Despite a prohibition on spraying, some organic wines contain as much as 80 to 220 micrograms of TFA per litre, whilst several conventional wines record lower values.

‘Nevertheless, the dividing line between organic and conventional where TFA in wine is concerned is far from clear-cut’

A link between pesticides and TFA contamination is nothing new, as fluorine is an element regularly used in the synthesis of agrochemicals. Recently, the Dutch consultancy CLM conducted an exploratory study into TFA in groundwater, in the course of which it catalogued the fluorine-containing pesticides authorised for use in Dutch agriculture. CLM tallies nine antifungal agents, nine herbicides and seven insecticides. A fluorine atom in a pesticide is not in itself a problem. What matters are the C-CF₃ groups, as these can form the highly persistent TFA as a breakdown product. The widely used antifungal agent fluazinam, for instance, has two C-CF₃ groups, and is therefore potentially a larger source of TFA than agents containing only one group, such as flufenacet.

Banned

Last year, researchers concluded that fluorine-containing pesticides are a significant source of TFA contamination in European agricultural areas. When comparing regions, they observe a relationship between agriculture and TFA in groundwater. The researchers venture a ‘back-of-a-beermat calculation’ based on the sales and use of 18 authorised pesticides containing a C-CF₃ group. They estimate that EU agriculture is responsible for an annual TFA emission of between 970 and 3,200 tonnes.

Since 2023, the EU has been working towards an eventual ban on virtually all PFAS, but this process is extremely complex and is progressing slowly, as C2W | Mens & Molecule has previously reported. The focus here is on the use of PFAS in food packaging, the chemical industry, electronics and computer chips. Pesticides do not fall within this framework, because the EU has a separate assessment system for agricultural pesticides. Nevertheless, attention to PFAS pesticides is growing, driven by concerns about the breakdown product TFA. At the request of the European Commission, the European Food Safety Authority (EFSA) has recently begun a review of the health reference values for TFA, working jointly with ECHA. Furthermore, Germany has submitted a proposal to ECHA, based on embryo research in rabbits, to classify TFA as ‘toxic to reproduction’. Such a more stringent classification could lead to a revised risk assessment and lower tolerance for the presence of TFA, and therefore also for the use of pesticides.

‘The irony is that this group of gases was, not so long ago, welcomed as a desirable innovation’

Air conditioning

Would a possible ban on fluorine-containing pesticides rid us of TFA? Certainly not, as there are many more sources, illustrated by a recent review in Environmental Science & Technology co-authored by environmental chemist Hans Peter Arp, among others. The chemical industry is one source of TFA, as it is both an intermediate and a waste product. Furthermore, much larger PFAS molecules can partially break down, generating TFA in the process. Finally, pharmaceutical companies manufacture medicines containing C-CF₃ groups. All these sources, however, pale into insignificance beside the TFA arising from the breakdown of a family of gases used in refrigeration, freezing and air conditioning. The irony is that this group of gases was, not so long ago, welcomed as a desirable innovation, since they are not harmful to the ozone layer and have barely any of the greenhouse effect associated with the old CFCs and HFCs.

But an advantage on the greenhouse front has its downside. The widely used tetrafluoropropene (HFO-1234yf) breaks down completely in the atmosphere to form TFA. Researchers estimate that in the EU, the use of HFO-1234yf in 2020 was responsible for the formation of 6,900 tonnes of TFA. To put the figures in perspective: in Germany, F-gases are estimated to be responsible for around 2,000 tonnes of TFA per year, whilst pesticides account for approximately 450 tonnes.

Researchers believe that a shift towards F-gases will multiply the global formation of TFA in the atmosphere several times over in the coming years. TFA does not linger long in the atmosphere, as it precipitates rapidly. Recent analyses in Germany and the United States, for example, measure between 0.20 and 0.30 micrograms of TFA per litre of rainwater. The consequences of this precipitation are also visible in measurements in wine and pasta, even when these are produced organically. TFA is persistent and mobile, and circulates predominantly within the water cycle. The substance also possesses a number of surprising properties in the natural environment: it accumulates in plants and food crops. Plants absorb water containing TFA and transpire it through their leaves, whilst the TFA remains behind. Researchers observe accumulation of TFA in maize, in the leaves and needles of trees, and in marsh plants. One study recorded a remarkable 3.8 grams of TFA per kilogram of dry weight in plants growing near a fluorochemical industrial facility in China.

Fruit purée

That TFA can be found in wine, bread and other plant-based foodstuffs therefore comes as no surprise. A few years ago, researchers also detected it in beer from 23 countries. And anyone who makes a cup of tea is unwittingly performing TFA extraction, although the quantities involved, at 2.4 micrograms, are relatively low. This spring, Eurofins analysed fruit juices and fruit purées. The average TFA concentration was around 34 micrograms per litre in orange juice, whilst in several samples of fruit purée, more than 25 micrograms per litre was recorded.

‘Plants absorb water containing TFA and transpire it through their leaves, whilst the TFA remains behind’

Avoiding TFA entirely by making clever choices at the supermarket has become an impossible task. The extent to which this poses risks is a matter of debate. According to a 2023 review in Molecular Toxicology, daily TFA exposure in humans remains well below the levels at which health risks would be expected. Whilst TFA is classified as harmful to aquatic life, it is not extremely toxic to humans or animals. It does not tend to accumulate in animals in the way that long-chain PFAS do. In short, TFA is excreted through urine and faeces, but since we are ingesting ever greater quantities of TFA on a daily basis, concentrations in our bodies could still rise in the years ahead.

The assessment of toxicological risks is largely based on animal studies, in which enlargement of the liver was observed in rats. The rat study lasted only 90 days, whereas lifelong exposure in humans is now guaranteed. In their review, Hans Peter Arp and colleagues therefore call for more realistic research. At the same time, they do not consider knowledge to be a prerequisite for action. They write: ‘The obvious place to start is by limiting the direct production of TFA and, more importantly, of TFA precursors, such as HFO-1234yf and pesticides such as flufenacet.’