The chemical compounds are all around you. They're on many fabrics, rugs and carpets, cooking pots and pans, outdoor gear, shampoo, shaving cream, makeup and even dental floss.
And a growing number of states have found them seeping into water supplies in recent years.
There's growing evidence that long-term exposure to the perfluoroalkyl and polyfluoroalkyl compounds, or PFAS, can be dangerous, even in tiny amounts.
The Environmental Protection Agency (EPA) is looking at how to respond to a public push for stricter regulation of the chemicals that have been in production, in our environment and in our bodies since the 1940s.
A decision from the agency is expected soon.
The EPA is considering a federal move to limit to toxic chemicals that may cause cancer and pregnancy complications for people who come into contact with them in bodies of water like the Rogue River (pictured, file image) in Michigan
At hearings around the country last year, local and state officials asked the agency to set a maximum level for PFAS in drinking water nationwide. It will take that, officials said, to stop contamination and hold polluting parties responsible.
But it's more than a US problem.
In Europe, Australia, Asia and elsewhere, regulators and consumers are confronting discoveries of PFAS contamination, especially around U.S. military bases, where they're used in firefighting foam.
WHAT ARE PFAS?: THE NON-STICK 'FOREVER COMPOUNDS' HAVE FOUND THEIR WAY INTO NEARLY EVERYONE
Industries use the chemicals in coatings meant to protect consumer goods from stains, water and corrosion.
DuPont says its scientists invented the earliest form of the nonstick compound in 1938. They were impressed with how water and grease slipped off the new substance and how it seemed never to break down - winning it the name 'forever compound.'
Various types soon were on the market, first in Teflon products. Thousands of variants have been produced since then, for a host of uses.
By the 1970s, manufacturers conceded that PFAS were building up in the bodies of employees who worked with them.
Recent scientific reports have estimated that nearly all people in the US have some PFAS chemicals in their blood.
Studies of workers exposed on the job and people who drank contaminated water, in addition to lab analyses of animals, have pointed to ties between some PFAS types and human illness.
Industries have phased out two of the most-studied versions of PFAS. Manufacturers say newer forms are safer and don't remain in the human body as long as older types. Some researchers say too little is known about them to be sure of that.
WHAT DOES THE SCIENCE SAY?: TINY TOXIC CHEMICALS MAY RAISE RISKS OF CANCER AND PREGNANCY ISSUES
DuPont agreed to a court-supervised public health study after a farmer in Parkersburg, West Virginia, brought a lawsuit blaming runoff from a PFAS facility for the deaths of his cattle.
The 2005-2013 study monitored and tested nearly 70,000 people who had been drinking water tainted with PFOA, one of two kinds of PFAS since phased out of production.
The study found 'probable links' between high levels of PFOA in the body and excessive cholesterol levels, ulcerative colitis, thyroid disease, testicular and kidney cancer, and problems in