This article originally appeared on Time. 

Drinking water for 15 million Americans in 27 states is contaminated with a toxic chemical that was used to make nonstick cookware, according to a new report released Thursday.

These chemicals, known as PFCs (perfluorochemicals), have been linked to cancer, thyroid disease and weakened immune systems. Even small concentrations in drinking water is considered a threat to public health, according to the report by the nonprofit Environmental Working Group and Northeastern University.

“It’s remarkable that the richest country on Earth can’t guarantee its citizens that their drinking water is completely safe and has no long-term health implications,” said Bill Walker, managing editor of the EWG in a press release.

Because PFCs have waterproof and nonstick properties, they were formerly used in hundreds of consumer products, “including cookware, outdoor clothing, food packaging and firefighting foam,” reports the EWG.

The EWG and Northeastern University created an interactive map combining data from the EPA and information from all publicly documented cases of PFC pollution coming from manufacturing plants, military airbases, civilian airports and fire training sites.

Although there is growing evidence of the health hazards of PFCs, there are currently no federal health regulations for these chemicals in drinking water. It has been 25 years since the EPA has added a new drinking water contaminant to the Safe Drinking Water Act.