EPA issued a drinking water health advisory for MTBE, a guidance document for water utilities and the public, in 1997. The Agency first listed MTBE in 1998 as a candidate for development of a national Maximum Contaminant Level (MCL) standard in drinking water. As of 2020 EPA has not announced whether it will develop an MCL. EPA uses toxicity data in developing MCLs for public water systems.
California established a state-level MCL for MTBE in 2000.