News Release

Arsenic in New England wells more widespread than thought

Peer-Reviewed Publication

American Chemical Society

Arsenic in the water of private wells in New England is more widespread than previously thought and its threat to residents may be growing because of increasing private well use, according to a new study by the U.S. Geological Survey. Chronic exposure to small amounts of arsenic has been linked to cancer. But people can keep their water's arsenic levels in check by careful monitoring and filtering, the researchers add.

The USGS study is the most comprehensive assessment to date of arsenic levels in the region's drinking water supply, the researchers say. It is scheduled to appear in the June 1 print version of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

Although researchers have known for some time that significant concentrations (10 to 50 parts per billion) of arsenic are present in groundwater in individual states within the New England region and may pose a health threat via drinking water, little was known about the nature and extent of the naturally occurring toxin's distribution on a regional scale until now, according to the researchers.

In the current study, the researchers evaluated data on arsenic levels for 1600 public and private water sources among the region's six states(Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont). The study focused primarily on the eastern part of the region, which contains the highest population density and where large amounts of groundwater are used for the water supply. Although there are some water supplies with high arsenic levels in western New England, the problem is not as extensive as it is in the eastern part of the region, they say.

"We found that elevated arsenic concentrations in private wells were much more prevalent than in public wells, in some cases by two to four times" says Joseph D. Ayotte, chief investigator for the study and a hydrologist with the USGS unit in Pembroke, N.H. "This may have important implications for the general public because over 20 percent of the region's population uses private wells for their water supply — much higher in some areas."

And the number of people with arsenic contaminated wells is likely to grow as the region's growing suburban population increasingly depends on drinking water obtained from existing and newly built private wells, the researcher says. High-growth suburban and rural areas in the region extend from the Boston area to Portland, Maine.

"These private wells are generally not regulated or mandated to reduce arsenic concentrations and thus may continue to provide residents with water containing arsenic greater than the current drinking water standard unless action is taken by individual well owners to reduce or eliminate the toxin," Ayotte warns.

While the Environmental Protection Agency currently mandates that public drinking water supplies should contain no more than 10 parts per billion of arsenic, almost a third of New England's private wells have higher levels. Wells in the region supply water for as many as 103,000 people, Ayotte estimates.

Public water supplies provide drinking water for the majority of the region's residents, particularly in the larger cities. These sources are more regulated by state and federal laws to reduce arsenic levels and are less likely to contain harmful amounts. By 2006, all public water suppliers are required to meet the EPA's stricter arsenic standard of 10 parts per billion (ppb), which is down from 50 ppb just a few years ago.

The correlation between high arsenic levels and private wells is strongly related to geology, Ayotte says. He and his associates found that the wells with the highest arsenic concentrations (greater than 10 ppb) tend to occur in groundwater sources within bedrock formations, and that these rock formations are contiguous and form a linear and predictable pattern concentrated in the eastern part of the region.

"What we've found is a pattern of high arsenic distribution within eastern New England that can be roughly described as an 'arsenic belt'," says Ayotte. "We can now use the relation to geology to gain a better understanding of where arsenic contamination is mostly likely to occur and how many people are affected."

Although no one is certain why the region has high concentrations of arsenic in its groundwater, increasing evidence suggests that the major source of arsenic is natural, originating from minerals found in rocks in the region. Manufacturing and many years of using pesticides and treated lumber may have also contributed to increased arsenic levels, but the extent of their contribution is unclear, Ayotte says.

While the study provides a clearer picture of arsenic distributions in the region, it has several caveats. Although private wells are widely available as water sources, little is known about how many of the region's residents actually drink water from them. Nor do authorities know how many residents use treatment systems to remove or reduce the arsenic concentration, Ayotte says. He and his associates are currently exploring these issues.

But there's good news: Current or prospective users of private wells can have their water tested for arsenic by state officials or private companies. If it's present, special filters can be purchased that significantly reduce arsenic levels. Bottled drinking water is an alternative.

Funding for this study was provided by the USGS National Water-Quality Assessment Program.

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The online version of the research paper cited above was initially published April 9 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to newsroom@acs.org or calling the contact person for this release.

EDITOR'S NOTE: Maps depicting arsenic concentrations in New England wells are available at:
http://www.eurekalert.org/images/release_graphics/ACSmap1.jpg
http://www.eurekalert.org/images/release_graphics/ACSmap2.jpg

High resolution photos are available at:
http://www.eurekalert.org/images/release_graphics/hi-resACSmap1.jpg
http://www.eurekalert.org/images/release_graphics/hi-resACSmap2.jpg


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