AWWA JAW70993

Perchlorate, which appeared on the first Contaminant Candidate List in 1999, is not currently regulated, but the U.S. Environmental Protection Agency (USEPA) is continuing to look at available data in order to determine whether a maximum contaminant level (MCL) should be set. The occurrence of perchlorate is a key factor that could affect the outcome of USEPA's regulatory assessment. Brandhuber and colleagues compiled data from existing perchlorate surveys, those done for the first Unregulated Contaminant Monitoring Rule as well as state surveys done by Arizona, California, Massachusetts, and Texas. They found that perchlorate was detected in 26 states, Puerto Rico, and the Mariana Islands and in at least one source of approximately 5% of the large (i.e., > 10,000 people) public water systems in the United States. The results of a 2007 phone survey indicate that some 50 mgd of potable water production has been taken off line as a result of perchlorate contamination. When detected, perchlorate was generally present in low concentrations (< 12 µg/L). If the USEPA decided to set an MCL for perchlorate, approximately 1% of all systems would be affected by a 20-µg/L MCL and 4% would be affected by a 2-µg/L MCL. This study will help USEPA understand the extent of perchlorate occurrence in U.S. drinking water, and could reduce the likelihood that USEPA will set a national MCL for perchlorate. Includes 42 references, tables, figures.