Replacement Chemicals for Ozone Spread New Pollutant Worldwide

Scientists have found that chemicals brought in to replace ozone-damaging CFCs are now behind a large rise in trifluoroacetic acid, a persistent pollutant known as TFA. This invisible substance is falling from the sky onto land, water, and ice across the world, including far-off places like the Arctic. The problem started years ago with efforts to protect the ozone layer, but these new chemicals break down into TFA over time. Between 2000 and 2022, about 335,500 tonnes of TFA landed on Earth's surface from the air. Levels keep climbing because many of these replacement gases stay in the atmosphere for decades.

Background

Back in the 1980s and 1990s, the world faced a big threat to the ozone layer from chlorofluorocarbons, or CFCs. These gases, used in refrigerators, air conditioners, and sprays, were eating away at the protective shield high in the sky that blocks harmful sun rays. Governments agreed to phase them out under the Montreal Protocol, a global treaty that has worked well to let the ozone heal.

To fill the gap, industry turned to hydrofluorocarbons, or HFCs, and later hydrofluoroolefins, known as HFOs. These gases do less harm to the ozone and were seen as a safe swap. They cool cars and homes without the old dangers. But over time, researchers noticed something unexpected. In the atmosphere, these replacements break apart and form TFA. This small molecule does not go away easily. Once it forms, it rains down or settles directly onto surfaces. It sticks around in water and soil for a very long time.

Teams from places like Lancaster University in the UK, along with experts from Australia, Norway, the US, and elsewhere, ran detailed computer models. They tracked how these gases move with weather patterns, break down, and deposit TFA. The work showed TFA reaching even the remotest spots. For example, almost all the TFA found in Arctic ice comes from these CFC replacements. Winds carry the gases far from cities and factories before they turn into the pollutant.

Key Details

The scale of the deposits is huge. From 2000 to 2022, the models put the total at 335,500 tonnes of TFA from the air. That's like a third of a million metric tons spread over land and water. Yearly amounts have jumped from around 6,800 tonnes in 2000 to much higher now. And it's not stopping. Peak deposits from these sources could come anytime from 2025 to 2100, depending on how use changes.

Sources and Spread

HFCs and HFOs are the main culprits from CFC swaps. One gas in particular, HFO-1234yf, is common in new car air conditioners. It breaks down fast into TFA. Anesthetics used in hospitals also add to the load. Beyond replacements, TFA comes from pesticides, solvents, pharmaceuticals, and other fluorinated chemicals. But the study pins CFC substitutes as the top source in the air.

TFA forms high up, then falls with rain or dry deposition. It shows up in rivers, lakes, groundwater, and even bread and pasta from tainted crops. In Europe, tests found levels three times higher in cereals than eight years ago. In the Arctic, ice cores show rising amounts over time, proof of long-distance travel.

"Our study shows that CFC replacements are likely to be the dominant atmospheric source of TFA," said Lucy Hart, a PhD researcher at Lancaster University and lead author. "This really highlights the broader risks that need to be considered by regulation when substituting harmful chemicals such as ozone-depleting CFCs."

"There is a need to address environmental TFA pollution because it is widespread, highly persistent, and levels are increasing," said Professor Ryan Hossaini, also from Lancaster.

What This Means

TFA builds up without breaking down. It ends up in oceans, the final sink. Some groups say current levels in water and people are below harm thresholds for humans. But others point to risks. The European Chemicals Agency calls it harmful to water life. Germany has suggested it may affect human reproduction. It turns up in blood and urine samples.

The steady rise worries experts. Even as HFCs get phased down under new climate deals, their long life means TFA will keep falling for decades. Calls grow for better tracking worldwide, especially in places like the UK. More tests in water, food, and ice could show the full picture. Regulators may need to look closer at replacements for replacements, like picking gases that do not form TFA.

Pesticides add another layer. They put TFA straight into soil and plants, skipping the air. Food contamination is rising, hitting everyday items. Broader sources like PFAS chemicals, once used in non-stick pans and waterproof gear, also feed the problem. These forever chemicals share TFA as a breakdown product.

Researchers stress the need for global work. Monitoring must expand to grasp all sources and effects. Without it, the invisible rain keeps falling, layer by layer, across the planet. Past fixes for ozone brought gains, but they opened this door. Now, the focus turns to closing it.