Six Things to Know About ‘Forever Chemicals’

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Almost half the tap water in the United States contains PFAS, a class of chemicals linked to serious health problems. In April the Environmental Protection Agency announced that, for the first time, municipal utilities will have to detect and remove PFAS from drinking water.

Here’s what you need to know.

In 1938 a young chemist working on refrigerants for Dupont accidentally discovered a new compound that was remarkably resistant to water and grease, a finding that would lead to the creation of the Teflon brand of nonstick cookware.

Today there are nearly 15,000 per- and polyfluoroalkyl substances, which collectively go by the acronym PFAS, according to a database maintained by the E.P.A.

The common link is that they have a special bond of carbon and fluorine atoms, making them incredibly strong and resistant to heat, water, oil and dirt. For that reason, PFAS is used for everyday items as varied as microwave popcorn bags, water-repellent clothing and stain-resistant carpets. PFAS are also in firefighting foam, cosmetics, shampoos, toys and even dental floss.

Everywhere, including drinking water. The indestructible nature that makes PFAS useful in some products also makes them harmful to human health. The chemicals are virtually indestructible and do not fully degrade, accumulating in the environment and the human body.

The chemicals are so ubiquitous that they can be found in the blood of almost every person in the country. One recent government study detected PFAS chemicals in nearly half of the nation’s tap water. A global study of more than 45,000 water samples around the world found that about 31 percent of tested groundwater samples that weren’t near any obvious source of contamination had PFAS levels considered harmful to human health.

According to the E.P.A., exposure to PFAS can cause damage to the liver and immune system and also has been linked to low birth weight, birth defects and developmental delays as well as increased risk of some prostate, kidney and testicular cancers. New research published in the past year found links between PFAS exposure and a delay in the onset of puberty in girls, leading to a higher incidence of breast cancer, renal disease and thyroid disease; a decrease in bone density in teenagers, potentially leading to osteoporosis; and an increased risk of Type 2 diabetes in women.

Many environmental advocates argue that PFAS contamination should have been dealt with long ago.

“For generations, PFAS chemicals slid off every federal environmental law like a fried egg off a Teflon pan,” said Ken Cook, president and co-founder of the Environmental Working Group, a nonprofit advocacy group.

Activists blame chemical companies, which for decades hid evidence of the dangers of PFAS, according to lawsuits and a peer-reviewed study, published in the Annals of Global Health, of previously secret industry documents.

The new E.P.A. rule requires utilities to reduce PFAS in drinking water to near-zero levels.

Not easily. In homes, filters attached to faucets or in pitchers generally do not remove PFAS substances. Under-sink reverse-osmosis systems have been shown to remove most but not all PFAS in studies performed by scientists at Duke University and North Carolina State University.

Municipal water systems can install one of several technologies including carbon filtration or a reverse-osmosis water filtration system that can reduce levels of the chemicals.

It could take years. Under the rule, a water system has three years to monitor and report its PFAS levels. Then, if the levels exceed the E.P.A.’s new standard, the utility will have another two years to purchase and install filtration technology.

But trade groups and local governments are expected to mount legal challenges against the regulation, potentially delaying it even before a court makes a final ruling. And if former President Donald J. Trump were to retake the White House in November, his administration could also reverse or weaken the rule.