They say nothing lasts forever. Nothing, that is, except a group of toxic chemicals that may be associated with testicular cancer, kidney cancer, high cholesterol and suppression of vaccine effectiveness in children. They are now in nearly all of our bodies, are found in the air and water around the globe, and they never go away. They are “Forever Chemicals.”

These are stain-repellent chemicals that we use in products throughout our homes, offices, schools, hospitals, cars and airplanes. They are characterized by a fluorine-carbon backbone. And the F-C bond, the Forever-Chemical bond, is quite amazing, representing one of the strongest bonds in all of organic chemistry.

When several F-C bonds are strung together, some really useful industry properties appear, including allowing air to pass through while blocking things such as grease, oil and dirt. This ability to act as a stain repellent is why we apply them to all sorts of products we like to keep clean, from carpets and furniture to camping gear. It’s also why we apply it to nonstick cookware — almost nothing can stick to the pan when we have a layer of these chemicals on the surface.

But this property comes with a pernicious dark side. The F-C bond is so strong that these chemicals never fully degrade. Ever. Like, for millennia ever.

Forever Chemicals have been used in products since the 1940s and, to confuse things as only scientists can, the terminology around these chemicals is so precise as to be useless. You might have heard them referred to as “stain-repellent compounds” or “highly fluorinated chemicals.” For years, many called them by their infamous toxic poster child “C8,” referring to the eight-carbon Forever Chemicals “PFOA” and “PFOS.” The most recent technical name for the Forever Chemicals we are talking about — the ones in consumer products and building materials — are perfluorinated or polyfluorinated alkyl substances, or PFASs. Rolls off the tongue, doesn’t it?