USGS: Chemicals Remain in Public Drinking Water After
Treatment
WASHINGTON, DC, December 9, 2008 (ENS)
Low levels of manufactured chemicals remain in public water supplies even
after they have been treated in selected community water facilities across
the country, according to new research conducted by the U.S. Geological
Survey and released today.
Water from nine selected rivers used as sources for public water systems was
analyzed for the study. The populations in communities served by these water
treatment plants vary from 3,000 to over a million.
Testing sites include the White River in Indiana; Elm Fork Trinity River in
Texas; Potomac River in Maryland; Neuse River in North Carolina;
Chattahoochee River in Georgia; Running Gutter Brook in Massachusetts;
Clackamas River in Oregon; Truckee River in Nevada; and Cache La Poudre in
Colorado.
Scientists tested water samples for about 260 commonly used chemicals,
including pesticides, solvents, gasoline hydrocarbons, personal care and
household products, disinfection by-products, and manufacturing additives.
The Harry Nice Bridge crosses the Potomac River at Morgantown, Maryland.
(Photo by Geoff Greene)
Low levels of about 130 of the chemicals were detected in streams and rivers
before treatment in the source water at the public water facilities. Nearly
two-thirds of those chemicals were also detected after treatment.
The most commonly detected chemicals in the source water were herbicides,
disinfection by-products, and fragrances. Most of the chemicals found were
at levels equivalent to one thimble of water in an Olympic-sized pool.
"Low level detection does not necessarily indicate a concern to human
health, but rather indicates what types of chemicals we can expect to find
in different areas of the country," said USGS lead scientist, Gregory Delzer.
"Recent scientific advances have given USGS scientists the analytical tools
to detect a variety of contaminants in the environment at low
concentrations; often 100 to 1,000 times lower than drinking-water standards
and other human-health benchmarks," he explained.
Delzer said that chemicals included in this study serve as indicators of the
possible presence of a larger number of commonly used chemicals in rivers,
streams, and drinking water.
Many of these chemicals are among those often found in ambient waters of 186
rivers and streams sampled by USGS since the early 1990s, and are correlated
with the presence of upstream wastewater sources or upstream agricultural
and urban land use.
About 120 chemicals were not detected at all.
Measured concentrations of chemicals detected in both source water and
treated water were generally less than 0.1 part per billion.
More than 75 percent of source water and treated water samples in this study
contained five or more chemicals.
"The common occurrence of chemical mixtures means that the total combined
toxicity may be greater than that of any single contaminant present," the
USGS said in a statement accompanying the report.
The USGS report identifies the need for continued research because the
additive or synergistic effects on human health of mixtures of man-made
chemicals at low levels are not well understood.
"Most of the man-made chemicals assessed in the USGS study are unregulated
in drinking water and not required to be monitored or removed," says Tom
Jacobus, general manager of the Washington Aqueduct, which provides drinking
water for one million people in the District of Columbia, Arlington County,
Virginia, and the City of Falls Church, Virginia,
"These findings are not surprising and they will be important in helping
regulators and assisting water utility managers arrive at decisions about
future water treatment processes," Jacobus said.
This study did not look at pharmaceuticals or hormones nor did it examine
the implications of the findings to ecosystems or aquatic health.
Although potential human-health effects and risk were not assessed in this
study, the USGS said that adverse effects to human health are expected to be
"negligible" based on comparisons of measured concentrations and available
human-health benchmarks.
Click here for the full source-water quality assessment and listing of
chemicals.
The USGS National Water-Quality Assessment Program is planning to complete
as many as 21 additional surface-water assessments through 2013. A companion
study is scheduled for release in 2009 that summarizes the occurrence of the
same chemicals in high-production wells and the associated treated water in
13 states.
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