A new study out of Dartmouth College estimates that arsenic in well water could be causing as many as 830 cases of cancer in the granite state.

Arsenic occurs naturally in New Hampshire bedrock, and in Southeast New Hampshire has been found in unsafe levels in 17 to 20 percent of domestic drinking water wells. Even in very low-doses, chronic consumption of arsenic is associated with a panoply of negative health impacts, including skin, lung and bladder cancer and decreased IQ in children.

Paul Susca from the Department of Environmental Services says the Dartmouth study estimates that if everyone with contaminated water got it treated, as many 650 cancer cases could be avoided.

“It noted in the report that that estimate is probably on the low side,” he says, “We’re hoping that well owners will use that information to understand the importance of testing their water and getting the appropriate treatment.