PFAS chemicals were darlings of chemical-industry leaders like 3M and DuPont for much of the 20th century following their discovery in the 1930s. PFAS were championed for their abilities to fight grease (Teflon) and repel water (Gore-Tex and Scotchgard). They were also used to make a firefighting foam used at military bases around the country.

But waste dumped from chemical-manufacturing plants can contaminate groundwater with PFAS chemicals, and they can also seep into lakes and other freshwater sources after firefighting foam gets used. PFAS are extremely persistent, so if they leech out of household products like cooking pans or if people unwittingly drink or inhale them, the chemicals bioaccumulate in our bodies. Then, they're pretty much with us for life.

"We've got about 80,000-plus chemicals that just go onto the market and, 'oh, we'll find out later down the road how that turns out for us,'" Brockovich said. "PFOA is a perfect example of this."

They can also easily build up in the human body as they move from the water we drink into our bloodstreams. Experts agree that every person has at least some PFAS in their system. Excessive exposure to the chemicals can be linked to health problems, including low birth rates, liver damage, high cholesterol, chronic kidney disease, asthma, attention-deficit/hyperactivity disorder (ADHD), immunization resistance in children, early menopause, and colon ulcers.