Low-Level Organic Chemicals in Rivers and Streams: Implications for Drinking Water

The nine community water systems tested are representative examples that serve populations of 3,000 to over a million. They include the Potomac River in the Maryland/Washington, D.C. area, the White River in Indiana, Elm Fork Trinity River in Texas, 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.

This briefing was held in cooperation with the USGS Office of Water Quality and its National Water-Quality Assessment (NAWQA) Program.

On December 5, the Environmental and Energy Study Institute (EESI) and the Water Environment Federation (WEF) held a briefing where the US Geological Survey (USGS) released new data collected at sources of public drinking water at nine sites across the country. The water was tested for more than 260 compounds, mostly man-made, including pesticides, solvents, gasoline hydrocarbons, personal care and household-use products, disinfection by-products, and manufacturing additives. Many of these chemicals have been found in surface water for years, but these studies specifically analyzed contaminants at drinking water intake locations, as well as the quality of the drinking water after treatment.

• USGS collected data from both source water and finished water on a monthly basis for at least one year.
• Results show that compounds such as herbicides, gasoline related compounds, personal care products, and other toxic compounds were found at drinking water intake sites. Concentrations were less than one part per billion (ppb) about 95 percent of the time.
• Of the 63 compounds found at concentrations greater than or equal to 0.1 ppb in source water, 36 have no Maximum Contaminant Level (MCL) regulations. For the compounds with regulated MCLs, the average concentrations never exceeded this benchmark level.
• Current water treatment systems are not designed to remove these compounds and in most cases, finished water contained the same concentration of contaminants as the source water.
• Water sources located close to agricultural or urban land had higher concentrations of contaminants than water sources surrounded by undeveloped land.
• More research is needed to evaluate the toxicity of the compounds without current data. More research is also needed to evaluate how mixtures of compounds interact. A mixture of compounds can have a different health effect in comparison to a number of compounds acting independently.