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Some of the most pristine parts of the planet have been contaminated with perfluoroalkyl and polyfluoroalkyl substances (PFAS), a class of chemicals that are nearly indestructible. Now, findings suggest that these 鈥�forever chemicals鈥� are travelling in surprising ways.

鈥淚f it can reach the pristine areas, then what can you say about the other areas?鈥� says at Coventry University in the UK.

PFAS are versatile 鈥� they are found in everything from the non-stick coating on pans to waterproof clothing because they can tolerate heat, repel water and resist degradation. But they don鈥檛 break down easily in the environment due to their strong carbon-fluorine bonds, and they have been linked to health issues in people and animals. Some, such as perfluorooctanoic acid (PFOA), are now banned in many countries.

PFAS have been found in waterways and oceans around the world, and some researchers believe the chemicals are mainly transported via water. In some cases, sea spray may turn them into aerosols, allowing them to travel far inland.

Kourtchev and his colleagues studied whether forever chemicals were spreading through the air as well. They measured PFAS concentrations in the air using sensors at the Amazon Tall Tower Observatory in Brazil, an Eiffel Tower-sized structure deep in the rainforest.

The researchers took samples of PFAS for about two weeks. Of the various types of chemicals, they only found significant concentrations of PFOA, which varied based on wind patterns. When the wind came from more remote parts of the rainforest in the north-east and east, they detected relatively low levels of PFOA at 320 metres above the ground 鈥� up to about 0.09 picograms (trillionths of a gram) per cubic metre of air. Just above the tree canopy, they found up to around 0.02 picograms per cubic metre.

The city closest to these sensors is Manaus, a chemical manufacturing hub 150 kilometres south-west of the tower. When the wind arrived from that direction, PFOA concentrations went up to more than 2 picograms per cubic metre at 320 metres above the ground and around 1.4 picograms per cubic metre near the canopy height.

This is the first time that scientists have measured PFAS levels in the Amazon鈥檚 atmosphere. Kourtchev says it is unclear whether these levels are dangerous, but researchers have linked PFOA to the disruption of hormones involved in reproduction and other key physiological processes. He says he worries about the effects on the wide diversity of local organisms and the Indigenous people who live in the area.

鈥淧FOA is an endocrine disruptor, potentially interfering with hormones like thyroid and reproductive hormones, which can affect metabolism, growth, fertility and development,鈥� says Kourtchev. 鈥淭he presence of PFOA in a pristine environment with unique flora and fauna could impact biodiversity by affecting the reproductive systems of fauna.鈥�

The source of PFOA pollution in Manaus is also uncertain, but Kourtchev says it could be getting pumped into the air from a chemical factory. at Utrecht University in the Netherlands says that PFOA may also enter the atmosphere during waste incineration in Manaus.

at Stockholm University in Sweden says he isn鈥檛 surprised the researchers detected PFAS in the Amazon because the chemicals have also been found in places as remote as Antarctica. 鈥淏ecause it is persistent and mobile, it has spread everywhere,鈥� says Cousins.