California Adopts MCL for Hexavalent Chromium

California has adopted a new hexavalent chromium (Chromium 6) maximum contaminant level (MCL) of 10 parts per billion (ppb) for drinking water. This is the second time the state established the MCL for Chromium 6. The first MCL in 2014 was invalidated through a court ruling for not adequately documenting economic feasibility. California is the only state to set its own MCL for Chrome 6 and to previously set an MCL of 50 ppb for total chromium that was lower than the federal total chromium MCL of 100 ppb.


The state will use a phased approach for compliance monitoring based on the number of water system service connections. For the largest water systems with 10,000 or more service connections, compliance monitoring will begin in two years. For more information, visit the California Water Boards website.