Two million Americans, living in close to 600 U.S. neighborhoods, are exposed to air pollution at levels that increase their risk of cancer significantly, a new report from the U.S. Environmental Protection Agency (EPA) has found.

While the EPA said all Americans have an increased cancer risk of greater than 10 in a million due to air pollution, those in the most polluted areas face cancer risks of greater than 100 in a million — a level the EPA generally regards as unacceptable.

For comparison, the average cancer risk in the United States is 36 in 1 million, according to the National-Scale Air Toxics Assessment.

“If we are in between 10 in 1 million and 100 in 1 million we want to look more deeply at that. If the risk is greater than 100 in 1 million, we don’t like that at all … we want to investigate that risk and do something about it,” Kelly Rimer, an environmental scientist with the EPA, told The Associated Press.

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