According to a new study led by researchers from Harvard T.H. Chan School of Public Health and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), for six million people in the U.S, their public drinking water supplies have the highest levels of a widely used class of industrial chemicals linked with cancer and other health problems.

Drinking water samples near industrial sites, military fire training areas, and wastewater treatment plants recorded high levels of polyfluoroalkyl and perfluoroalkyl substances (PFASs) which exceed federally recommended safety levels.

PFASs have been used over the past 60 years in industrial and commercial products ranging from food wrappers to clothing to pots and pans. They have been linked with cancer, hormone disruption, high cholesterol, and obesity. Although several major manufacturers have discontinued the use of some PFASs, the chemicals continue to persist in people and wildlife. Drinking water is one of the main routes through which people can be exposed.

"These compounds are potent immunotoxicants in children and recent work suggests drinking water safety levels should be much lower than the provisional guidelines established by EPA," said Elsie Sunderland, senior author of the study and associate professor in both the Harvard Chan School and SEAS.

"For many years, chemicals with unknown toxicities, such as PFASs, were allowed to be used and released to the environment, and we now have to face the severe consequences," said lead author Xindi Hu, a doctoral student in the Department of Environmental Health at Harvard Chan School and Environmental Science and Engineering at SEAS. "In addition, the actual number of people exposed may be even higher than our study found, because government data for levels of these compounds in drinking water is lacking for almost a third of the U.S. population-about 100 million people."

The researchers looked at industrial sites that manufacture or use PFASs; at military fire training sites and civilian airports where fire-fighting foam containing PFASs is used; and at wastewater treatment plants. Discharges from these plants-which are unable to remove PFASs from wastewater by standard treatment methods-could contaminate groundwater. So could the sludge that the plants generate and which is frequently used as fertilizer.

Those exposed to PFASs at a young age, according to one research project, were found to have lower-than-expected levels of antibodies against diphtheria and tetanus, for which they had been immunized. The findings suggested that PFASs, which are known to interfere with immune function, may be involved in reducing the effectiveness of vaccines in children.