Scientists discover concerning new source of ‘forever chemicals’ in drinking water

A group of potentially toxic “forever chemicals,” mostly coming from prescribed drugs, may be contaminating drinking water for millions of Americans, as wastewater treatment plants fail to remove them — and climate change may be making the situation even worse, according to a new report.

Scientists analyzed water samples flowing through eight large publicly owned wastewater plants across the US, all of similar size and using similar technologies to those serving 70% of the population.

Even with advanced treatment technologies, they found forever chemicals and compounds able to transform into them were being discharged into rivers and lakes where they can reenter the drinking water supply. Roughly 23 million Americans could be exposed to these forever chemicals from wastewater alone, the study found.

“We’re identifying really large amounts of chemicals that we know very little about,” said Bridger Ruyle, an environmental engineering scientist at NYU and an author of the study published Monday in the Proceedings of the National Academy of Sciences.

This is especially concerning as treated wastewater is expected to make up an increasing proportion of drinking water supplies as climate change-fueled drought shrinks water sources, Ruyle told CNN.

Forever chemicals are so-called for their ability to stay in the environment — and in people’s bodies — for a very long time without breaking down. There are nearly 15,000 of them, known collectively as PFAS, or perfluoroalkyl and polyfluoroalkyl substances.

Since the 1950s, PFAS have been used in a huge range of consumer products, prized for their ability to resist oil, grease, heat and water. They make clothes waterproof, carpets stain-resistant and pans non-stick. But their prolific use has come at a cost. Even at very low levels, they have been linked to a range of health conditions, including thyroid problems, infertility and some cancers.

People are exposed to PFAS in many ways, but drinking water is an important one. Almost half the tap water in the US is contaminated, according to a 2023 study.

Wastewater treatment plants play a major role, Ruyle said. They receive PFAS-contaminated water from homes and industry and about 50% of drinking water plants in the US are downstream from one of them, he added.

In 2024, the Environmental Protection Agency introduced rules to dramatically reduce concentrations of six PFAS in drinking water. However, the study found the chemicals the EPA regulates made up only about 8% of the potentially hazardous compounds found in the water samples analyzed. The majority comprised unregulated chemicals including other PFAS and pharmaceuticals.

Drug companies use compounds classified as PFAS because they are very hard to degrade, Ruyle said. This can increase the concentration of drugs in people’s bodies.

While that’s an advantage for the effectiveness of the drugs, it’s a problem everywhere else. A molecule that’s hard to degrade in the body, is also hard to degrade in a wastewater plant or in rivers and lakes, Ruyle said.

The study also found climate change could increase exposure. Lakes and rivers shrink during drought, but the amount of wastewater humans produce does not, Ruyle said. This means there is less natural water to dilute the chemicals in wastewater before it enters drinking water plants.

In many parts of the country, especially those susceptible to drought, water reuse is already an important source of drinking water, said David Andrews, acting chief science officer at the Environmental Working Group, which monitors exposure to chemicals including PFAS. “These water systems are particularly vulnerable,” said Andrews, who was not involved in the study.

“This study highlights how wastewater treatment plants are not currently equipped to clean up the contamination,” he told CNN.

Denis O’Carroll, a professor of civil and environmental engineering at the University of New South Wales, also not involved in the research, said the study “suggests that many PFAS go undetected using traditional laboratory methods.” He told CNN the analysis was consistent with his own recent research which found PFAS levels in surface and groundwater around the world are being underestimated.

The study is also significant because it quantifies different sources of PFAS at wastewater treatment plants and finds those from pharmaceuticals “may be of concern,” he said. It’s important to understand the sources of PFAS in order to reduce them he added.

Much more research is still needed, Ruyle said. “There is a really large universe of PFAS that are much more prevalent, that are being found at these major sources, (and) we need to get an understanding of what their own health risks are,” he said.

There are actions people can take, including filtering tap water. But experts say the best solution is find ways to stop PFAS entering the environment in the first place.

“We need to address the problem at the source,” Ruyle said, “rather than installing even more advanced, more expensive, more resource-intensive technologies at drinking water utilities or asking people to buy specialized home treatment systems.”

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