Occurrence of MTBE and other gasoline oxygenates in CWS source waters

Results from two national surveys indicate that the gasoline oxygenate methyl tertiary butyl ether (MTBE) is one of the most frequently detected volatile organic compounds in source waters used by community water systems in the United States. Three other ether oxygenates were detected infrequently but almost always co-occurred with MTBE. A random sampling of source waters across the United States found MTBE in almost 9% of samples. In geographic areas with high MTBE use, the compound was detected in 23% of source water samples. Although MTBE concentrations were low (<1 µg/L) in most samples, some concentrations equaled or exceeded the drinking water advisory of 20 µg/L set by the US Environmental Protection Agency. The frequent detection of even low concentrations of MTBE demonstrates the vulnerability of US source waters to anthropogenic compounds, indicating a need to include MTBE in monitoring programs to track the trend of contamination.