The peer-reviewed study is the first to quantify the health and economic impacts of nitrates in drinking water in the United States, the Environmental Working Group says.

Nitrate pollution in Iowa’s drinking water may be responsible for up to 300 cases of cancer annually in the state, a new study shows.

Four states — Iowa, Delaware, Arizona and California — have “average levels of nitrate contamination that, at the high end … could cause more than 10 cases of cancer per 100,000 people a year,” according to the Environmental Working Group, a nonprofit research and advocacy group, based in Washington, D.C.

The peer-reviewed study is the first to quantify the health and economic impacts of nitrates in drinking water in the United States, the group says.

Nationally, the study shows nitrate pollution in drinking water may cause up to 12,594 cases of cancer a year, carrying an estimated health care cost of up to $1.5 billion annually.