Natural Weathering Of Bedrock Believed To Be Source Of Contaminant
Arsenic concentrations that exceed current recommended federal levels for drinking water are 10 times more likely to be found in domestic wells than in municipal water sources in New Hampshire, according to a study by researchers at Dartmouth College. Arsenic in drinking water is linked to certain types of cancer in humans.
Results of the study, involving nearly 1,000 water samples, are scheduled to appear in the May 1 print issue of the peer-reviewed journal Environmental Science & Technology, published by the American Chemical Society, the world's largest scientific society. The study was initially published March 20 on the journal's web site.
The article claims that water from domestic New Hampshire wells contains "significantly more arsenic than water from municipal sources," in some cases more than three times the current maximum contaminant level (MCL) of 50 parts per billion (ppb) established by the U.S. Environmental Protection Agency.
A report issued last week by the National Academy of Sciences concluded that the current EPA standard was too high to adequately protect against the risk of cancer, and needed to be addressed "promptly."
Several clusters of elevated arsenic levels in 'bedrock' wells were found in the southeastern and south central parts of the state, mostly near the cities of Manchester and the state capital, Concord, according to the study. Domestic bedrock wells that are drilled deep into New Hampshire's underlying granite base generally have much higher arsenic levels than shallow surface wells, say the researchers.
The article cites another study published last year by the U.S. Geological Survey, involving water samples from several New England states, Massachusetts, Maine, New Hampshire, Rhode Island and Vermont, that showed ten to 15 percent of the region's domestic bedrock wells exceeded the EPA guideline.'"/>