A research team led by Harvard University has found elevated concentrations of organofluorine in US municipal wastewater. More than 60% consisted of widely prescribed fluorinated pharmaceuticals, while 6 federally regulated perfluoroalkyl and polyfluoroalkyl substances (PFAS) made up less than 10% of total extractable organofluorine in samples.

The work is published in the journal Proceedings of the National Academy of Sciences,

PFAS are synthetic chemicals with thousands of variations containing organofluorine structures with a powerfully bonded chain of carbon and fluorine atoms. The strong bond gives the molecules nonstick properties that are widely used for consumer products like cookware, the inner lining of food packaging, waterproofing, and stain-resistant carpets and clothes.

Because the carbon-fluorine bond is one of the strongest, these chemicals do not degrade easily in the environment, earning the compound the title of “forever chemical.” Global contamination of soil and groundwater systems with PFAS is so replete that it has even been detected high on the Tibetan plateau, carried there by rain.

Currently, there are no safe and cost-effective strategies for reducing PFAS contamination once it is in the environment. Wastewater treatment facilities serve most of the US population, yet less than 25% of measured organofluorine is removed even under advanced processes.

In the study titled “High organofluorine concentrations in municipal wastewater affect downstream drinking water supplies for millions of Americans,” researchers sampled 8 large wastewater treatment facilities with similar design capacities for organofluorine levels.

Researchers used bulk and targeted methods to detect extractable organofluorine, including PFAS, precursors, and fluorinated pharmaceuticals. A national wastewater dilution model was applied to simulate how discharges mix with drinking water intakes under average and low flow conditions.

Less than 10% of the extractable organofluorine in wastewater originated from six regulated PFAS. Pharmaceuticals accounted for 62% to 75% of the measured organofluorine load. Removal rates did not exceed 24% at any facility.

Over 20 million Americans were estimated to rely on drinking water supplies prone to contamination levels above regulatory thresholds when wastewater-derived PFAS were considered—a significant concern.

While this is treated wastewater release, not the water coming out of the home tap, it will mix with other water sources and “eventually” be redirected to household use again. That “eventually” might happen quicker than most people imagine.

If you live anywhere near a river, your community likely uses the water from that river. So do the towns and cities upstream and downstream of your community. They purify the river water for household use, use it, treat it in a separate facility as wastewater and then mix the treated wastewater back into the river. The process repeats over and over again downstream, occasionally diverting for farming, commercial or industrial uses.

By the time a coastal city uses water, it may already have been purified, used and treated hundreds or thousands of times, or at least mixed with water that has been.

The Mississippi River has over 4,500 publicly owned water treatment works (POTWs). These POTWs treat the water and send it downstream again in a water reuse system that flows through 10 states along the river and a watershed that reaches 21 more.

© 2025 Science