Rainwater everywhere on Earth contains so much cancer-causing ‘forever chemicals’ that it should be classified as unsafe to drink, a new study has warned.

The chemicals – per- and polyfluoroalkyl substances (PFAS) – are man-made chemicals that spread in the atmosphere, and can now be found in rain and snow in the world’s remotest places.


The chemicals are produced by industry, and are extremely persistent in the atmosphere, the researchers warn.

As scientists have understood more about the toxicity of these chemicals, the guidelines for ‘safe’ levels have become more and more strict – meaning that rainwater would now be classified as ‘unsafe’.

Lead author Professor Ian Cousins, of Stockholm University, said, “There has been an astounding decline in guideline values for PFAS in drinking water in the last 20 years.

“For example, the drinking water guideline value for one well known substance in the PFAS class, namely the cancer-causing perfluorooctanoic acid (PFOA), has declined by 37.5 million times in the U.S.”

“Based on the latest US guidelines for PFOA in drinking water, rainwater everywhere would be judged unsafe to drink.

“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.”

The Stockholm University team measured the atmospheric presence of PFAS for the past decade.

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