Comparison of MCLs and PHGs for Regulated Contaminants in Drinking Water

This page compares maximum contaminant levels (MCLs) and public health goals (PHGs).


MCLs are adopted as regulations. They are health protective drinking water standards to be met by public water systems. MCLs take into account not only chemicals' health risks but also factors such as their detectability and treatability, as well as costs of treatment. Health & Safety Code §116365(a) requires a contaminant's MCL to be established at a level as close to its PHG as is technologically and economically feasible, placing primary emphasis on the protection of public health.

Along with the MCL, a regulated chemical also has a detection limit for purposes of reporting (DLR), the level at which the we are confident about quantification being reported.


PHGs are established by the Office of Environmental Health Hazard Assessment (OEHHA). They are concentrations of drinking water contaminants that pose no significant health risk if consumed for a lifetime, based on current risk assessment principles, practices, and methods. OEHHA establishes PHGs pursuant to Health & Safety Code §116365(c) for contaminants with MCLs, and for those for which MCLs will be adopted.

Public water systems use PHGs to provide information about drinking water contaminants in their annual Consumer Confidence Reports. Certain public water systems must provide a report to their customers about health risks from a contaminant that exceeds its PHG and about the cost of treatment to meet the PHG, and hold a public hearing on the report.

Review of MCLs in Response to PHGs

Once OEHHA establishes or revises a PHG for a contaminant with an MCL, we determine whether the MCL should be considered for possible revision. For a chemicals so designated, we subsequently conduct an in-depth risk management analysis to determine whether or not to propose a revision. For more information, see MCL review status.