Forever chemicals are everywhere. They’re in our nonstick pans, our makeup, our clothing. They’re in our drinking water and our soil and even our bodies. They’ve been around for decades, and they’re not going away anytime soon.

Forever chemicals refers to per- and polyfluoroalkyl substances, also called PFAS, a class of synthetic chemicals used since about the 1940s in consumer products. They have unique properties that impart benefits, such as stain- or water-resistance, due to the strong carbon-fluorine bond in their makeup. That strong bond, though, means these chemicals don’t really degrade. PFAS will stick around for thousands of years, polluting the environment and our bodies; exposure to PFAS has been linked to increased risk of cancer, decreased fertility, developmental delays, and more. And this class of chemicals isn’t small—there are more than 12,000 kinds of PFAS.

If PFAS have been around for decades, why does it seem like we’ve only recently started hearing about them? One reason is that scientists are constantly learning more about these chemicals, testing more sources for them, and finding them nearly everywhere they look, prompting more research and more publicity. Another reason might be the “forever chemicals” moniker, which has helped move PFAS from the pages of jargon-filled research papers and into the public conversation.

The term was officially coined in 2018 in a Washington Post op-ed by Joseph G. Allen, an associate professor at the Harvard T.H. Chan School of Public Health who also runs the Harvard Healthy Buildings Program. “I’ve been in this field a long time and saw what was happening with these chemicals, and I was concerned about persistent toxic chemicals,” he says. “Normally, when we think about persistent chemicals, it’s bad enough on the order of decades. With these chemicals, the persistence is on the order of millennia.”

Allen saw the growing body of research showing that these chemicals weren’t breaking down, and were linked to health effects like lipid metabolism and testicular cancer. “What I didn’t hear was the public really aware, despite our field being hyper aware, of this as a major problem,” he says.

Scientific language can, of course, be inaccessible to those outside of science. “I mean, ‘per- and polyfluoroalkyl substances’ is a name only a chemist could love,” Allen says. It doesn’t quite roll off the tongue for the average person. And PFAS, though easier to pronounce (pea-fass) doesn’t mean much to anyone at first glance, either. “I wanted to talk about them in a way that might be more accessible to a lot of people and include in their name their key feature—that they are forever,” Allen says. “​​The decisions we’re making in terms of these products and their use will last through our lifetime and well beyond.” Along with invoking one of their key features, the name “forever chemicals” is a play on their molecular bond: Allen switched around the commonly called carbon-fluoride bond to a “fluorine-carbon bond” in his op-ed, linking the F-C bond to the Forever-Chemical property.

Erik D. Olson, senior strategic director for health and food with the NRDC, doesn’t remember the exact moment he first heard the term “forever chemicals,” but thinks it was around five years ago. Since then, he’s noticed it entering widespread use, in part for its functionality. “I think it does encapsulate some of the concern, and in a very simple way, that these chemicals stick around,” he says. “It’s something that the average person can immediately grasp, so that’s really important.”

That “forever” part is just one aspect of the PFAS problem, though. Along with being “extremely persistent,” Olson notes that PFAS are toxic at very low doses—”parts per trillion, parts per quadrillion”—and that they’re “extremely mobile,” as in they don’t stay in one place. “They tend to diffuse themselves out into the environment,” he says. PFAS have been found in the blood of 97% of Americans, and have also reached around the world, ending up in Antarctica and in the bodies of animals like tigers, monkeys, and otters. But even knowing that PFAS are toxic, it’s difficult to tackle the problem because they’re so ubiquitous: They’re in camping gear, carpets, furniture, lotions, nail polish, and food packaging, just for starters.

Recently, the EPA announced a proposal for limits on PFAS in drinking water. Both Allen and Olson emphasized the importance of the move. “It’s a historic first step toward taking this issue seriously,” Olson says. But they also noted that it’s limited: The proposal would address six types of PFAS. There are more than 12,000 that exist. This is an example of the “chemical wack-a-mole” Allen says that is common for our regulatory system: “The script had been, ‘Okay, we found out this chemical is bad, sorry we used it for a few decades. Here’s another one, we think is safer,’ and it turns out it’s not,” Allen says. What Allen and other experts want instead is for the entire class of PFAS chemicals to be banned.

That sort of change may be far down the road, but the PFAS problem isn’t going anywhere. There’s been an explosion of interest in the issue, and likely more to come. That can’t all be credited to the “forever chemicals” nickname, but it doesn’t hurt. “If you go into a cocktail party and start talking about PFHXS [a type of PFAS] and a bunch of chemical soup terms, peoples’ eyes glaze over,” Olson says. “But if you start talking about ‘forever chemicals,’ people understand inherently that this is something they ought to be concerned about.”