Organic Compounds in Potomac River Water Used for Public Supply near
Washington, D.C., 2003–05Prepared as part of the National
Water-Quality Assessment Program, Source Water-Quality Assessment
By Michael J. Brayton, Judith M. Denver,
Gregory C. Delzer, and Pixie A. Hamilton
Organic compounds
studied in this U.S. Geological Survey (USGS) assessment (PDF in right column) generally are
man-made, including, in part, pesticides, solvents, gasoline
hydrocarbons, personal care and domestic-use products, and refrigerants
and propellants. A total of 85 of 277 compounds were detected at least
once among the 25 samples collected approximately monthly during 2003–05
at the intake of the Washington Aqueduct, one of several community
water systems on the Potomac River upstream from Washington, D.C. The
diversity of compounds detected indicate a variety of different sources
and uses (including wastewater discharge, industrial, agricultural,
domestic, and others) and different pathways (including treated
wastewater outfalls located upstream, overland runoff, and ground-water
discharge) to drinking-water supplies. Seven compounds were detected
year-round in source-water intake samples, including selected herbicide
compounds commonly used in the Potomac River Basin and in other
agricultural areas across the United States. Two-thirds of the 26
compounds detected most commonly in source water (in at least 20 percent
of the samples) also were detected most commonly in finished water
(after treatment but prior to distribution). Concentrations for all
detected compounds in source and finished water generally were less than
0.1 microgram per liter and always less than human-health benchmarks,
which are available for about one-half of the detected compounds. On the
basis of this screening-level assessment, adverse effects to human
health are expected to be negligible (subject to limitations of
available human health benchmarks).
Friends of the North Fork comment:
USGS Drinking Water Study:
The United
States Geological Survey (USGS) recently released a report entitled
Organic Compounds in Potomac River Water Used for Public Supply Near
Washington, D.C, 2003-2005. 26 compounds were identified in either or
both the source water (raw river water from the Potomac) and finished
(treated drinking water) water that scientists analyzed. Interestingly,
USGS detected some of the same herbicides in finished water that
Friends’ 2007 study found in water we analyzed from the North Fork in
2007 (River Health Report, 2008). Thus, agricultural herbicides, like
atrazine, are not being removed from drinking water during the water
treatment process in Washington area facilities. It is likely therefore
that these chemicals are not removed from drinking water in the North
Fork watershed in cases where the raw water is being taken from the
river. Notably, USGS did not analyze samples for hormones or
pharmaceuticals. While the amounts of most of the compounds identified
in the USGS study are quite low, human health benchmarks have not been
established for many of the chemicals and their synergistic and
cumulative effects on humans and animals have not been established.
Friends of the North Fork are currently developing a report on how best
to test for these chemicals in our drinking water supply and we will be
asking state and local officials to conduct the necessary testing so
that the citizens of the Valley are aware of what organic chemicals are
in their drinking water. The USGS study is part of an ongoing survey
of the Nation’s drinking water.
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