DRINKING WATER PROTECTION SERVICES Q. What is the legal maximum contaminant level (MCL) for arsenic allowed in California drinking water?
A. Prior to January 23, 2006, the Federal and State MCL for Arsenic were 50 parts per billion (ppb). On January 23, 2006, the U.S. Environmental Protection Agency (E.P.A.) adopted a more stringent Federal maximum contaminant level (MCL) of 10 ppb for Arsenic. On November 28, 2008, the State of California followed by also adopting the MCL standard of 10 ppb into the California Code of Regulations. The current legal MCL for potable water in California is 10 ppb.
