Public water supplies serving six million people found to contain up to 25 times the safe limit of toxic chemicals.

More than six million people in the US are drinking water that contains poisonous industrial chemicals linked with cancer and other health problems at levels higher than official safety limits, according to a major new study.

Researchers from Harvard University and other institutions used information about 36,000 water samples collected nationwide by the US Environmental Protection Agency (EPA) from 2013-2015.

They found that chemicals known as PFASs were present in 194 out of 4,864 public water supplies. And 66 water supplies had at least one sample that was above the EPA safety limit.

The highest concentration was found in Newark, Delaware, where the level of one kind of PFAS was 25 times higher than the safe limit. The worst problems were found in watersheds near industrial sites, military bases and wastewater treatment plants, the researchers reported in the journal Environmental Science & Technology Letters.

PFASs – polyfluoroalkyl and perfluoroalkyl substances – can be used in everything from food containers such as pizza boxes and non-stick cooking utensils to clothing, carpets and furniture. Only last year a group of scientists expressed concern about the increasing number of these kinds of chemicals in the environment, noting a “growing body” of evidence that they can cause cancer, obesity, low birth weight and even delay puberty.