ABSTRACT
In 1999, California’s Department of Health Services (DHS) proposed a 13 micrograms per liter (mg/L)or 13 ppb primary maximum contaminant level (MCL) for MTBE.3 A contaminant’s primary MCL indicates the concentration that is not to be exceeded in statewide public water supplies. The secondary MCL for MTBE has been set at 5 mg/L. This secondary MCL for MTBE is known as the taste and odor threshold — this threshold also indicates a concentration that is not to be exceeded in statewide public water supplies.
