(CNN) Potentially toxic chemicals are in the drinking water supplies of several major metropolitan areas in the US, including Miami, New Orleans and Washington, DC, according to a new report from the Environmental Working Group (EWG).

The findings, published by the environmental advocacy group this week, suggested that PFAS, manmade chemicals that are extremely persistent in the environment and in human bodies, could be found in major water supplies in the US.

The group tested the drinking water at 44 sites in 31 states and Washington for PFAS chemicals.

Of the areas tested, only Meridian, Mississippi, had no detectable levels of the toxic chemicals. The community draws its drinking water from wells more than 700 feet deep, the group said.

The water supplies in Brunswick County, North Carolina, and Quad Cities, Iowa, contained the highest levels of the chemicals, more than 100 times the EWG's suggested limit. The advocacy group's recommended PFAS limit is 1 part per trillion in drinking water, about 70 times stronger than federal recommendations.

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