Could your water be making you dumber? If it has arsenic in it, it might, a new study suggests. Researchers followed 272 Maine schoolchildren over the course of five years, and found that those whose water contained arsenic tended to have lower IQs, the Portland Press Herald reports.

"Everyone was a little taken aback by that," says University of New Hampshire professor Amy Schwartz, who coordinated the tests along with Columbia University researchers. "People shouldn't panic, but be informed." Arsenic occurs naturally in groundwater, which means that people who get their water from wells may be consuming it.

The effect—as much as 5 or 6 points on IQ tests—shows up in water with arsenic levels of just 5 parts per billion, well below the 10 parts per billion the EPA considers safe.

In Maine, roughly 20% of wells hit that threshold. Researchers recommend that people who rely on wells invest in a filtration system. "As a consumer, I know I wouldn't wait around for a new standard," Schwartz says.

Of course, filtration produces waste of its own—which is why a team in California is working on a process to embed the arsenic in concrete bricks that could potentially be used in construction, Gizmodo reports.

(Last year, arsenic was found in some beer.)

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