What we know about PFAS

A federal database shows there are now more than 14,000 PFAS or PFAS-like chemicals in existence.But we know very little about the health effects of most, said Cheryl Murphy, the director of the Center for PFAS Research at Michigan State University.The two most studied chemicals in the class — PFOS and PFOA — have been tied to several serious health conditions. Studies have revealed that the chemicals can tamp down the human immune system and reduce vaccine protection, especially in children. PFAS exposure has also been connected to cardiovascular problems and delayed development. And the Environmental Protection Agency says PFOA is likely a human carcinogen and evidence suggests PFOS may be, too.While PFOA and PFOS have been voluntarily phased out by the chemical industry, they still remain in the environment. Meanwhile, experts say manufacturers have developed a constellation of replacements. This generation of chemicals is still being studied, but the EPA says some newer PFAS have also been shown to affect the liver, the kidneys, the immune system, and human development.

What regulations on PFAS chemicals currently exist?

In 2016, the EPA set its drinking water health advisory for PFOS and PFOA at 70 parts per trillion. Then, earlier this year, it drastically cut the recommended level to less than 1 part per trillion. Last month, the EPA also proposed classifying both chemicals as hazardous substances.The agency also recently set final health advisories for two other chemicals in the class, which are considered replacements for PFOS and PFOA.Some states have adopted their own drinking water standards, and California recently announced a ban on PFAS in textiles and cosmetics set to take effect in 2025.