Study identifies sources of drinking water contamination for millions of Americans

Researchers trace possible sources to fire training areas, airports, industrial sites, and wastewater treatment plants.

A recent analysis of federal drinking water data finds that public water supplies for more than six million Americans contain highly fluorinated chemicals—PFOA and PFOS—at levels above new guidelines set by the U.S. Environmental Protection Agency (EPA). The study traces possible sources of contamination to military fire training areas and airports, as well as industrial sites and wastewater treatment plants. This is the first study to examine a nationwide dataset of highly fluorinated chemicals in drinking water and to use spatial analysis to investigate the sources of contamination.

Highly fluorinated chemicals, broadly known as PFASs (per- and polyfluoroalkyl substances), have been associated with numerous health effects including kidney and testicular cancer, thyroid disruption, high cholesterol, and obesity. They are routinely found in consumer products such as pizza boxes, non-stick pans, waterproof clothing, and stain-resistant carpets. They are also used in some firefighting foams.

The study, published online August 9 in Environmental Science & Technology Letters, relied on drinking water data from EPA, which requires public water supplies to monitor periodically certain unregulated contaminants. Among drinking water samples that contained highly fluorinated chemicals, each additional military site within a hydrologic unit (an area of connected source waters) was associated with a 10 percent increase in PFOA levels, and a 35 percent increase in PFOS levels.

Although the study puts the number of Americans exposed to unsafe levels of PFASs at six million, that may be a gross underestimate, says co-author Laurel Schaider, a water research expert at Silent Spring Institute. “EPA’s water monitoring program includes a limited number of small public water supplies and no private drinking water wells,” she says.

Some 44 million Americans get their drinking water from private wells and another 52 million rely on smaller public water supplies that are not part of EPA’s testing. “That’s a lot of people who might be exposed to contaminated water, but without further testing, we have no way of knowing, which is very concerning,” says Schaider.

The continued use of firefighting foams containing PFASs at military sites and airports is a growing problem. “During firefighting training exercises, large volumes of these toxic chemicals wash into surface and ground waters and can end up in our drinking water,” said co-author Arlene Blum, executive director of the Green Science Policy Institute in Berkeley, Calif. “Such persistent chemicals should only be used when essential, and never for practice drills.”

A new generation of shorter chain fluorinated chemicals are replacing older long chain substances. “Like the older substances, these other fluorinated compounds do not break down in the environment and may be similarly toxic,” says lead author Elsie Sunderland, an environmental chemist at the Harvard John A. Paulson School of Engineering and Applied Sciences.

Schaider also points out there may be other sources of contamination with potential health effects. In a previous study of private wells on Cape Cod, she traced the presence of PFASs in people’s drinking water to septic systems serving residential areas. Although the levels of PFASs detected in her study fell below EPA’s health guidelines, their presence in drinking water is still a concern, she says.

For instance, exposure to PFASs has been associated with effects on the immune system, says Philippe Grandjean of the Harvard T.H. Chan School of Public Health, who is another author on the new study. In a separate study, his group found that early life exposure to PFOA and PFOS reduces immune responses to vaccines that persist into adolescence.

"Our research has documented harm to the human immune system from PFOA at levels much below those that were detectable in the EPA database and even more water supplies are likely to be contaminated at these low levels," he says. "The EPA advisory limit for PFOA and PFOS is much too high to protect against toxic effects on the immune system."

In addition to Schaider, Blum, Sunderland, and Grandjean, the other co-authors of the study include scientists from the California Department of Toxic Substances Control, Colorado School of Mines, Environmental Working Group, EPA’s National Exposure Research Laboratory, University of Rhode Island, and University of California at Berkeley.