Read the full article by Maggie Koerth and Michael Tabb (FiveThirtyEight)

“Maggie Koerth: I have two important numbers for you this year. Some good news. And some bad news.

First, there’s four … That’s the number of harmful per- and polyfluorinated chemicals, or PFAS, that the Environmental Protection Agency released new concentration guidelines for this year. This is the good news.

Then, there’s four thousand seven hundred … That’s roughly the number of different PFAS chemicals out there, globally. They’re present in thousands of products you buy and use. They’re even in your drinking water. And this entire category of chemicals, including the ones developed to be ‘safer’ replacements, have increasingly been shown to be dangerous to human health.

PFAS are a problem that date back to your grandma’s day. They were invented during the Great Depression and have been used in non-stick coatings on products like pots and pans since the 1940s. Since then, they’ve become part of how we make waterproof and stain-resistant fabrics and carpets, fire-fighting foam, cleaning products, paint, food packaging and more.

But these ‘forever chemicals’ don’t break down. They just build up in the environment. And in the early 2000s, scientists started finding these chemicals in soil and water … and, eventually, in human blood.

To put it mildly … this is not good. Just a few parts per trillion in drinking water have been linked to a wide variety of health issues, from thyroid and immune response problems, to high cholesterol, to testicular cancer. This summer, the National Academies of Sciences reported that almost 100 percent of Americans have been exposed.

Despite all of this … or maybe, behind all of this … is the fact that PFAS aren’t well regulated. The EPA didn’t even have guidelines for what an acceptable concentration of PFAS in drinking water might be until 2016. At that time, they said that 70 parts per trillion was an acceptable amount of PFAS to find in water supplies. Now they’ve dropped that by more than a thousandfold. Scientists aren’t sure they even have the tools to measure PFAS at that level.” …