In patches all over the US, an ancient layer of sediment in the Earth’s crust is rich in arsenic, a chemical element toxic to humans. And some 2 million people drawing water from private wells in the US may be getting exposed to it in levels above the legal limit, according to research published Wednesday (Oct 18) in Environmental Science & Technology.
Because they aren’t covered by the Federal Safe Drinking Water Act, private wells aren’t subject to the same government contamination tests that public water systems undergo.
Arsenic is a serious toxin. Recent research—like this paper that studied births in Ohio—found that babies of pregnant mothers who drank arsenic at levels below the federal standard were more likely to be born with a range of problems.
Arsenic is also a recognized carcinogen; Scientists at the US Environmental Protection Agency have concluded that if 100,000 women consumed the legal limit of arsenic each day, 730 of them eventually would get lung or bladder cancer, according to the Center for Public Integrity.
The EPA lowered the limit to 10 ppb from the previous 50 ppb limit in 2001—but the EPA initially proposed to lower it to 5 ppb.
Arsenic can’t be removed from water with chlorine, or by boiling.