Potentially harmful levels of naturally occurring arsenic, uranium, radium, radon and manganese have been found in some bedrock ground water that supplies drinking water wells in New England, according to a new U.S. Geological Survey (USGS) study.
While the presence of contaminants, such
as arsenic, in some ground water already was known, this new study identifies
several that had not been previously identified. This new report also provides information on
the type of bedrock geologic formations where high concentrations are most
likely to be found, which will help identify areas most at risk of
The results highlight the importance of
private well owners testing and potentially treating their water. While public water supplies are treated to
ensure that water reaching the tap of households meets federal requirements,
there are no such requirements for private supplies, which serve more than 2.3
million people in the region. All of the contaminants identified can be reduced
or eliminated through a variety of treatments.
"The same geologic forces which
gave rise to the spectacular mountains and architecturally significant rock
quarries of New England are also responsible, over time, for leaching trace
contaminants into the ground water that can be harmful to human health," says
USGS Director Marcia McNutt. "This study helps focus attention on where
and what the risk factors are such that citizens who depend on private wells
can get their water tested to ensure peace of mind."
Among the findings, arsenic in untreated
samples exceeded federal safety standards for public drinking water at 13
percent of sites – nearly double the national rate. Manganese exceeded its
human-health benchmark in more than 7 percent of wells tested. Radon exceeded
the U.S. Environmental Protection Agency’s (EPA) proposed standards in 33
percent of wells. Additionally, uranium, which is easily measurable, was found
to be a significant predictor of the presence of other forms of radioactivity
(radon, radium, gross alpha radioactivity) that are a cause of concern for
The study, part of an ongoing national
effort by the USGS to systematically assess the quality of the Nation’s most
important aquifers, is the most comprehensive study of the quality of New
England’s bedrock ground water to date.
“The concentrations above human health
benchmarks and the wide variety of natural and man-made contaminants found show
the vulnerability of crystalline rock aquifers that millions of people rely on
to produce safe drinking water,” says USGS scientist and lead author Sarah
Flanagan. “The well-to-well variability of water quality from bedrock aquifers
in the region underscores the importance of testing public and private wells
"The bedrock aquifer in New England
is a crucial drinking water resource, supplying water for the majority of our
2.3 million private well owners and many small public water systems in the
region," notes Curt Spalding, regional administrator of the EPA’s New
England office. "This and other scientific studies on bedrock ground water
quality conducted by the USGS provide the scientific foundation for
implementing protection programs to ensure that all New Englanders have access
to safe, clean drinking water."
For this study, scientists examined
water-quality data from more than 4,700 public-supply wells that were sampled
for the EPA Safe Drinking Water Program from 1997 to 2007 and 117 private wells
sampled by the USGS National Water-Quality Assessment Program from 1995 to
2007. The samples included only well water from crystalline rock aquifers found
in most of New England and small portions of northern New Jersey and southern
New York State.
Depending on concentrations and the
period of time someone consumes the water, among the potential health issues
associated with drinking water containing these contaminants at levels above
human health benchmarks include various types of cancer; reproductive and
developmental problems; kidney and blood diseases; diabetes; and a weakened
“This study confirmed many areas already
known to have ground water with high levels of arsenic and radiochemicals and
revealed for the first time, the potential fluoride hotspots in parts of the
White Mountain region of northern New Hampshire,” says Flanagan.
These hotspots are locations with
naturally occurring fluoride that can exceed drinking water standards.
“We also found that high concentrations
of many naturally occurring compounds in ground water were related to specific
bedrock formations,” adds Flanagan.
In addition to natural sources, human
activities affected the quality of ground water from New England’s crystalline
rock aquifers. The researchers found
sodium and chloride in water sources, both naturally occurring as well as that
from road salt; nitrates; MtBE (methyl tert-butyl ether) and chloroform; and,
rarely, pesticides. The concentrations of these contaminants were all below
levels of human health concern, but some, such as chloride, had the potential
to impact aquatic organisms.