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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 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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USGS Fact Sheet Washington Drinking Water |
