Per-and poly-fluoroalkyl substances—commonly known as PFAS—are a group of over 14,000 human-made chemicals that have been popular since the 1950s for their diverse skills in resisting heat, water, grease and stains.

They’ve been commonly found in household products like non-stick frypans, clothing, cosmetics, insecticides, and food packaging, as well as specialty industry products, like firefighting foam.

But despite their broad skillset, the chemicals have a dark side: they’re known as ‘forever chemicals’ as once they’re in the environment—or our bodies—they don’t degrade further.

PFAS have been linked to environmental and health issues, including some cancers, but a lot remains unknown about the true scale and potential impacts of the problem—including how much is in our water supply.