Some molecules are made to last. Trifluoroacetic acid, TFA, is two carbons, three fluorines and an acid group, the smallest of the forever chemicals. It forms in the sky when escaped fluorinated refrigerants break down, then falls with the rain and stays. On 25 October 2026 Eawag published the Swiss numbers.

The map and the curve

The work is by Alexandra Kroll of the Ecotox Centre, Martin Scheringer and colleagues, published in Aqua & Gas 10/2026. In the national NAQUA groundwater monitoring for 2022–2023, TFA turned up at 508 of 517 stations. About 70 % of values sat below 1 µg/L and 95 % below 2 µg/L, with higher readings in farming regions. Those 517 points exist because cantonal and federal technicians have walked to the same wells, season after season, for years. Without them, this story would not exist.

The rivers carry the time axis. The network average rose from 0.09 µg/L in 1996/97 to 0.52 µg/L today, roughly six times higher. Per Eawag, atmospheric deposition, mainly from refrigerant F-gases, is the largest known national source: about 24.5 t a year over 2021–2023, more than four times the level of thirty years ago.

←TODAY: TFA sits in 508 of 517 Swiss groundwater stations, and rain delivers about 24.5 t a year.
→3012: Zurich’s aquifers carry a chemical memory of every refrigerant circuit that ever leaked above them.
Fulcrum: a molecule that does not break down turns each leak into a permanent entry, so the cheapest cleanup is the gas you never released.

Why the filter gives up

The carbon–fluorine bond is why TFA persists; its size is why it slips past treatment. Small, polar and very soluble, it runs with the water. Conventional treatment and activated carbon do not remove it, and Germany’s Umweltbundesamt reports the same for ozonation and UV. Reverse osmosis removed more than 99.9 % in a pilot, but it trades a water problem for a high energy bill and a concentrated waste stream. Switzerland has no legal TFA limit yet. The Ecotox Centre’s chronic quality criterion is 16 µg/L; the EU’s aggregate PFAS limit works out at 2.2 µg/L for TFA alone, a value agricultural groundwater already reaches in places. In June 2026, ECHA’s Risk Assessment Committee concluded that TFA should be classed as toxic to reproduction, category 1B. Chronic effects remain poorly understood, which is why persistence is the number to watch.

The line onto the site

BAFU lists refrigerants escaping from air conditioners and heat pumps as one TFA source. That sentence needs its neighbour, from the Swiss heat-pump association FWS: “Es gibt keinen Grund mit der Installation einer Wärmepumpe abzuwarten” — there is no reason to wait with installing a heat pump. The heat pump remains the backbone of the Swiss heat transition. The question sits one level down, in the fluid inside the circuit and in F-gas chemistry that was scaled before its breakdown products were understood.

The revised ChemRRV (Annex 2.10) largely follows the EU F-Gas Regulation of 2024, and the first refrigerant tightenings take effect on 1 January 2027. Installed units with a GWP below 2500 may keep running and be serviced for life. FWS adds: “Zudem sind bereits Geräte mit natürlichen Kältemitteln auf dem Markt verfügbar” — units with natural refrigerants are already on the market. Propane (R290) and CO₂ (R744) form no TFA.

Atelier: For a Swiss office specifying heat pumps on housing, schools or renovations, the refrigerant is usually the installer’s choice, settled late and rarely recorded: a planner’s decision hiding in plain sight. Monday move: add a mandatory “refrigerant type” field to your heat-pump and cooling tender template, prefilled with R290 or R744, so every other variant has to justify itself in writing.

Hack: Turn the national deposition figure into a number you can hold over a roof. Spread 24.5 t across Switzerland’s 41,285 km², then turn “more than four times in thirty years” into an annual rate.

dep_t = 24.5                     # t/yr, Eawag 2021-23
area_m2 = 41_285e6               # Switzerland, m²
per_m2 = dep_t * 1e9 / area_m2   # mg per m² per year
growth = 4 ** (1 / 30) - 1       # at least 4x over 30 years
print(f"{per_m2:.2f} mg/m²/yr, ≥{growth:.1%} per year")

It prints about 0.59 mg/m² a year and a minimum growth rate of 4.7 % a year: roughly 120 mg landing each year on a 200 m² roof. Small, and it never leaves — the whole problem in two numbers.

From where I sit, the chemistry that hurt us was rarely the one that failed in the lab. It was the one that shipped before anyone read the half-life of what it became. Kroll’s line is the one to keep: remediation is “considerably more difficult than preventing further releases.”

Open your current heat-pump specification today and write R290 or R744 into the refrigerant line.

Sources & Further Reading

• Primary: Eawag — Trifluoroacetic acid: a challenge for water protection and drinking water supply
• Reinforcing: FWS — Kältemittel