Researchers out of Europe say global levels of man-made "forever chemicals" have made rainwater unsafe to drink around the world — even in the most remote areas. The study, published in peer-review journal Environmental Science and Technology on Tuesday from researchers at Stockholm University and ETH Zurich, argues that guideline values – amounts considered acceptable – for per- and polyfluoroalkyl substances (PFAS) in drinking water, surface water and soil have fallen "dramatically" over the last 20 years "due to new insights into their toxicity."