As the world faces climate change, population growth, and dwindling fresh water supplies, more people will rely on treated wastewater to sustain their daily lives.
But even after treatment, sewage contains high levels of harmful “permanent chemicals” that are already contaminating the drinking water of millions of Americans, researchers say. said in a study published Monday that analyzed sewage samples.
The study, led by researchers at Harvard University and New York University, found elevated levels of six chemicals known as PFAS (per- and polyfluoroalkyl substances) in the samples. These chemicals, which have been linked to cancer and other diseases, are known as permanent chemicals because they do not break down in the environment. Last year, the Environmental Protection Agency began regulating PFAS in drinking water.
The researchers found that the samples contained even higher amounts of organic fluorine. Organofluorines are a broad group of chemicals that include PFAS and are used in pharmaceuticals, refrigerants, and nonstick coatings. Most of these chemicals are unregulated, and the health effects of exposure to many of them are still unknown.
“What are these other compounds? Are they another PFAS that industry has migrated to that we're not measuring?” said Bridger Lyle, an assistant professor of environmental engineering at New York University who led the study. spoke. “What does that mean for exposure?”
The study, published in the Proceedings of the National Academy of Sciences, found that wastewater treatment plants are not effectively removing these compounds from wastewater. In fact, at most sites, the researchers found that PFAS in wastewater became even more concentrated after treatment.
The researchers said the pollution is especially concerning given that water shortages in many parts of the United States are forcing wastewater to be recycled or released into rivers and lakes. And if that wastewater isn't sufficiently diluted before re-entering the drinking water supply, a growing concern as overuse and climate change reduce water flows, “you'll have problems with contamination,” Professor Lyle said. said.
About 50 percent of the country's drinking water supply is downstream of one or more sewage treatment plants, he added. The study used modeling to show that PFAS from wastewater already contaminates the drinking water of up to 23 million people in the United States.
The results “underscore the importance of further suppressing ongoing sources of PFAS,” the researchers concluded.
A new study highlights how widespread pollution complicates efforts to reuse wastewater, which includes contaminated water from businesses and factories as well as sewage from households. The sludge left after wastewater treatment is also used to fertilize farmland across the country, and PFAS contamination in that sludge has also raised concerns about this practice.
