Health

Updated: 5 October 2026.

If you want to know how much trifluoroacetic acid, or TFA, is in your tap water, the nearest groundwater reading will not tell you. Nor will a bottle labelled ‘mineral water’ necessarily contain less. What matters is the concentration in the drinking water supplied to your home.

TFA is now found throughout Switzerland’s groundwater, though concentrations vary markedly. Detection alone does not establish an acute health risk. But the substance’s extraordinary persistence, its continuing release into the environment and the European Food Safety Authority’s stricter assessment mean it cannot sensibly be dismissed.

To understand your exposure, you need to know the concentration in your water, how much you take in through the rest of your diet and where the contamination comes from.

Groundwater readings are not tap-water results

In 2022 and 2023, the Federal Office for the Environment (FOEN) tested nearly 550 sites through the National Groundwater Monitoring programme, NAQUA. TFA was detected across Switzerland, but the results varied considerably.

At Alpine sites above 1,000 metres, concentrations consistently remained below 0.6 micrograms per litre. In catchments dominated by arable farming, readings were often between 1 and 5 micrograms per litre. At two nearby locations in north-western Switzerland, an industrial discharge produced much higher concentrations of 14 and 23 micrograms per litre respectively.

These measurements do not map what comes out of every kitchen tap. Depending on the region, suppliers may draw water from several groundwater abstraction points, springs or lakes. They can blend different sources, take an abstraction point temporarily out of service or treat raw water before distribution.

To establish your own exposure, ask your local supplier whether it has tested the drinking water as supplied and what concentration it found. A nearby NAQUA result is not a substitute. Mineral water also comes from natural water resources, so only an analysis of the particular source can show whether it contains less TFA.

EFSA has tightened the safety benchmark

On 22 July 2026, the European Food Safety Authority (EFSA) published a new health assessment of TFA based on around 170 studies and scientific opinions. Its analysis focused on changes in thyroid hormones observed in animal studies. The most sensitive effect concerned thyroxine, a hormone with an important role in metabolism, growth and development.

EFSA reduced the acceptable daily intake, or ADI, from 0.05 to 0.014 milligrams of TFA per kilogram of body weight per day. It also established an acute reference dose for the first time, set at 0.07 milligrams per kilogram of body weight.

The ADI is not a drinking-water limit. It estimates the total amount a person can consume each day over an extended period without an appreciable health risk, according to current knowledge. It covers all food and drink, not water alone.

The reassessment did not make Swiss tap water dangerous overnight. It showed, however, that the previous safety benchmark was too permissive in light of newer evidence.

Food remains the missing part of the picture

TFA can pass from water into plants and potentially enter the food supply. Switzerland’s Federal Food Safety and Veterinary Office (FSVO) is investigating its occurrence in plant-based foods. There is not yet a complete, up-to-date assessment of total exposure through water and food for the Swiss population.

Research gaps remain as well. EFSA considers it unlikely that TFA damages genetic material. However, long-term studies of its potential to cause cancer are notably lacking, as are sufficient data on possible effects on the developing immune system. When setting the new ADI, the authority therefore added a further factor of five to the usual safety factor.

These gaps do not indicate an immediate public-health emergency. They do make broad reassurance premature.

A pollutant that travels with water

TFA belongs to the large group of substances known as PFAS. It is a fully fluorinated molecule that is exceptionally small, highly soluble in water and virtually non-degradable under natural environmental conditions. Because it barely binds to soil, it travels with water: from rainfall into the ground, through deeper layers with percolating water and eventually into groundwater.

That journey may take years or decades. According to FOEN, groundwater measurements made today can therefore reflect past emissions. The reverse also matters: substances released now may affect water resources far into the future.

The central concern is not dramatic acute toxicity, but the more troublesome combination of persistence, mobility and continual replenishment.

Twenty-five tonnes deposited by rain each year

FOEN’s precipitation monitoring shows the scale of TFA’s spread. Rainwater contains an average of about 0.6 micrograms per litre, roughly four times the concentration measured in the 1980s. Across Switzerland, this amounts to an estimated 25 tonnes of TFA deposited by rainfall each year.

Some TFA forms in the atmosphere when certain fluorinated refrigerants and propellants break down, then returns to the surface in precipitation. Rain accounts for only part of the contamination.

FOEN records significantly higher concentrations beneath agricultural land. Numerous plant-protection products contain structures that can form TFA as they degrade; the federal office currently identifies 26 authorised active substances with this potential. Local industrial releases, including those carried in wastewater, add to the total. Conventional sewage treatment plants cannot reliably remove such a small, stable molecule.

Treatment separates TFA; it does not destroy it

Ordinary activated carbon does not reliably capture TFA because the substance is so small and dissolves so readily in water. UV treatment and ozonation offer no simple answer either.

Tight-membrane processes such as reverse osmosis can largely separate TFA from drinking water. But separation is not destruction. The TFA becomes concentrated in the rejected water stream, leaving contaminated residue that must be dealt with. Energy use, capital costs and maintenance compound the problem.

For an individual household, filtration may be a technical choice. For a public water supplier, it becomes an infrastructure and economic challenge. Once a persistent substance has spread through the water cycle, removing it costs considerably more than preventing its formation and release.

Swiss regulation has yet to set a dedicated limit

On 27 May 2026, the Federal Council opened a consultation on changes to maximum PFAS levels in drinking water. The consultation closed on 18 September 2026 and included proposals for closer alignment with European drinking-water regulation. It has not yet produced a dedicated Swiss maximum level for TFA.

Switzerland has already acted on two plant-protection active substances. Approval for flufenacet and tritosulfuron was withdrawn with effect from 1 July 2025. Other active substances capable of potentially forming TFA remain in use.

Even an immediate end to every problematic release would not quickly clear the contamination already present. Water moves slowly below ground, while TFA persists for an exceptionally long time. The most effective intervention is therefore upstream: preventing more TFA from entering the environment.

Ask for the result from your own supply

Ask your local water supplier whether it has measured TFA in the finished drinking water it distributes, and request the result. Do not infer your personal exposure from a regional groundwater figure or from the term ‘mineral water’.

The wider issue begins well before the tap. Drinking water starts in the atmosphere, on farmland, in industrial processes and across the catchments feeding springs and groundwater abstraction points. A release in any of these places may take years to reach the public supply.

EFSA’s tighter assessment is an early warning, not a cause for alarm. With a substance that barely breaks down, the decisive intervention comes before the tap: what does not enter the water today will not have to be removed in the future.