Manganese in Drinking Water

• Division of Drinking Water requests OEHHA establish PHG for manganese – June 2, 2026
• Division of Drinking Water issues revised manganese notification and response levels – June 2, 2026

Manganese is the 12th most abundant element of the earth’s crust, which makes it ubiquitous in the environment. It can naturally occur in both surface water and groundwater sources.

Manganese is an essential nutrient and enzyme cofactor that is naturally present in many foods and available as a dietary supplement, but despite its nutritional benefits, adverse health effects can be caused by over-exposure. There is substantial evidence that demonstrates that exposure to manganese at high levels can pose a neurotoxic risk (ATSDR, 2012; US EPA, 2004; WHO, 2021). Occupational manganese exposure has been shown to cause a distinct neurologic condition known as manganism, a clinical syndrome of cognitive and motor dysfunction that resembles Parkinson disease.

The main route of manganese absorption is through the gastrointestinal tract, but absorption also occurs in the lungs following inhalation exposure of airborne manganese. There is little evidence that dermal contact with manganese results in significant absorption through the skin and dermal contact is not generally viewed as an important source of exposure (ATSDR, 2012).

Children, specifically formula-fed infants, may particularly be susceptible to possible effects of high levels of manganese exposure because they absorb and/or retain more manganese than adults (ATSDR, 2012).

Given the possibility of neurological impacts at high concentrations, particularly for formula-fed infants, attention to the response level of 0.20 mg/L is appropriate. Similar advisory levels for manganese have been established by the US EPA, which has a manganese health advisory level of 0.3 mg/L (USEPA, 2004), and the World Health Organization, which has a manganese provisional health-based guideline value of 0.8 mg/L (WHO, 2021).

The following documents are provided to assist water systems in responding to the updated notification and response levels of manganese, including templates to use when providing public notice to their customers:

• Manganese In California's Drinking Water Phase 1 - Communication Plan
• Manganese Frequently Asked Questions
• Templates for Public Notification Related to Manganese Secondary MCL, Notification Level, Response Level

Manganese is regulated by a 0.05-mg/L secondary maximum contaminant level (MCL) (see drinking water regulations). The secondary standard was established to address issues of aesthetics (discoloration), not health concerns. In California, secondary MCLs are enforceable. (USEPA's 0.05-mg/L federal secondary standard for manganese is a non-enforceable guideline.)

Secondary MCLs are enforceable standards in California but are applicable only to community systems. Thus, noncommunity systems, particularly nontransient noncommunity (NTNC) systems such as schools and workplaces, do not receive the benefits of the secondary standard.

Notes:

1. Average manganese source concentrations in 2020 (left) and median treated effluent manganese concentrations in 2020 entering the distribution system for sources with active manganese treatment (right).
2. Sources are active, standby, and proposed sources. Treated effluent concentration is the average manganese concentration after treatment. For water systems with more than one treatment plant reporting manganese effluent concentrations, the median of the average treated manganese concentrations was used (shown on the map).
3. Not all water systems are treating for manganese. Additionally, a water system with manganese treatment may not be treating all of its sources with manganese detections. In the map, it is assumed that if a water system has manganese treatment installed, the manganese concentrations entering the distribution system are the same as the median treated effluent concentration.
4. Treated manganese concentrations entering the distribution system are not representative of manganese concentrations at the consumer tap

• Agency for Toxic Substances and Disease Registry (ATSDR). (2012). Toxicological Profile for Manganese.
• U.S. Environmental Protection Agency (EPA). (2004). Drinking Water Health Advisory for Manganese.

• Information on Chemicals and Contaminants in Drinking Water
• Information for Public Drinking Water Systems
• Drinking Water Programs