Rainwater is now unsafe to drink worldwide because of 'forever chemicals,' study suggests

It's now unsafe to drink rainwater around the world because of the growing presence of "forever chemicals," a new study suggests.

In the study, published Aug. 2 in the peer-reviewed journal Environmental Science & Technology, researchers point to the dangers of per- and polyfluoroalkyl substances, or PFAS.

PFAS are a family of human-made chemicals used in countless products today, from food packaging to waterproof clothing. They can spread in the atmosphere and are now found in every corner of our Earth – including rainwater, snow and even human blood. PFAS are dubbed "forever chemicals" because they can last "thousands of years," Clean Water Action notes.

A host of possible serious health consequences has been associated with PFAS, including cancer, infertility and pregnancy complications, immune system problems and increased cholesterol, according to researchers at Stockholm University and ETH Zurich.

According to the EPA, most uses of PFOA and PFOS were "voluntarily phased out by U.S. manufacturers," but some products still use them.

In the Aug. 2 study, the team of environmental scientists noted that worldwide guidelines for levels of PFAS in drinking water have "progressively decreased over the last 22 years," notably because of new research and awareness about the toxicity of PFAS.

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The declines underline growing concern about the chemicals, and what amount is safe to drink. For example, the researchers found that the U.S. Environmental Protection Agency health advisory for allowable levels of perfluorooctanoic acid (PFOA), one PFAS variant associated with cancer risks, had declined by a factor of 37.5 million over the years – most recently from 70 parts per trillion (ppt) to 0.004 parts per trillion.

The researchers found the levels of PFOA in drinking water in every part of the world, even some of the most remote areas, exceeded the EPA's contamination guidelines.

That means "rainwater everywhere would be judged unsafe to drink," Ian Cousins, lead author of the study and environmental science professor at Stockholm University, said in a university press release. "Although in the industrial world we don’t often drink rainwater, many people around the world expect it to be safe to drink and it supplies many of our drinking water sources.” 

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The study also found that levels of other PFAS variants, such as perfluorooctanesulfonic acid (PFOS), also exceeded U.S. guidelines in numerous rural and urban regions around the globe.

“The extreme persistence and continual global cycling of certain PFAS will lead to the continued exceedance of the above-mentioned guidelines,” Martin Scheringer, a co-author of the study and a professor based at ETH Zurich in Switzerland and Masaryk University in the Czech Republic, said in the news release.

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The researchers concluded that the safe "planetary boundary" for PFAS has been exceeded, carrying immense consequences for environmental and human health.

The study underlined that action to prevent further damage was urgent – such as "large investment in advanced cleanup technology" and "rapidly restricting uses of PFAS wherever possible."