Arsenic levels in bedrock well water have been found at a rate greater than three times the national average along a corridor stretching from eastern Maine to northeastern Massachusetts, according to a U.S. Geological Survey report released Monday.

“In eastern New England, like along coastal Maine, is what we call ‘the Arsenic Belt,’” Sarah Flanagan, one of the report’s authors, told the Bangor Daily News on Tuesday evening. “It’s a poison that takes a long time to show effects. You could drink well water with detectable levels of arsenic for 20 years and maybe not show any signs of it. But if you drink it long enough, bladder cancer and diabetes are among the consequences of low levels of arsenic.”

Additionally, bedrock wells in a significant portion of western Maine produce water with what scientists are describing as an unusually high uranium concentration, the study found.

The report features analysis of water tests from nearly 5,000 bedrock wells across New England, northern New Jersey and southern New York state — more than 4,700 public-supply wells between 1997 and 2007, as well as 117 private residential wells between 1995 and 2007.

Within that sample size, of the approximately 2,000 wells tested for arsenic, 13 percent were found to have more of the naturally occurring poison than the maximum concentration level allowed by federal environmental regulators for municipal drinking water supplies, a threshold of 10 micrograms per liter. The national average testing rate is about 7 percent, Flanagan said.

Of the 492 wells tested along the “Arsenic Belt” — a stretch of what scientists know as calcareous metasedimentary bedrock — the rate found to have more arsenic than the federal cutoff jumped to 23 percent, she said.

“Water designated for public use (by cities and towns) is treated to levels mandated by the (U.S. Environmental Protection Agency),” Flanagan said. “But the private wells are not regulated by either the states or the EPA. We think the people most at risk are the people who rely on bedrock wells and have not, for one reason or another, gotten their water tested.”

In a splotch of peraluminous granite predominantly in western Maine, the study found nearly 45 percent of the bedrock wells tested had rates of radioactive uranium greater than the 30 micrograms per liter allowed in public drinking supplies. That localized uptick compares with a rate of 14 percent across the rest of the study area.

Flanagan said some of the elements included in the report — such as iron and manganese — are easy for homeowners to detect in their well water because they stain laundry and discolor pipes.

“But with arsenic and uranium, you wouldn’t taste it, you wouldn’t smell it, and you wouldn’t see it,” she said. “The only way you’d know if you have high levels would be if you tested.”

She said state agencies such as the Maine Department of Environmental Protection are well equipped to answer questions about well water tests. Flanagan said water can be treated for nearly all naturally occurring elements and said many of the study’s results simply provided documentation to confirm levels long assumed by researchers because of underlying rock in the region.

“It’s just the way the rocks are — the way they were formed and deposited — there was just more arsenic in some areas,” she said.

Flanagan added that the report included some good news as well: The report found “virtually no pesticides” in the well water tested, meaning the vast majority of Maine’s bedrock wells are not being infiltrated by manmade chemicals.

Interestingly enough, she said, traces of seawater still can be found in some bedrock wells south of Augusta, lingering remnants of when a larger portion of the state was under water more than 12,000 years ago.

“It’s kind of hard to believe that the seashore was up in Augusta at one point,” Flanagan said. “One consequence of that is that old seawater could be found in bedrock wells.”

FOR MORE, see the Bangor Daily News at bangordailynews.com.

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