Life Cycle of Methyl tert-Butyl Ether in California Public Water Supply Wells

We have utilized the California Department of Public Health Water Quality Analyses database, with approximately 250000 results for methyl tert-butyl ether (MTBE), to evaluate the extent of MTBE in public water supply wells in California and how these impacts have changed over time. These data show that MTBE has never been detected in >98% of 13183 public water supply wells that have been tested for MTBE. The number of wells with first-time detections of MTBE peaked in 2000 and has decreased by 80% since that time. For the 188 wells in which MTBE has been detected at least once, MTBE was not detected in the most recent analysis of 142 of these wells. Tetrachloroethene, another common groundwater contaminant, has been detected more commonly, and new detections are declining more slowly. These results indicate that the impact of MTBE on public water supply wells has peaked and is declining.