Manganese in Drinking Water

Announcement

The Division of Drinking Water (DDW) has initiated the process of revising the current notification and response levels for manganese.

  More information can be found on the Drinking Water Notification Levels page.

Background Information

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, 2004). 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 are considered to be particularly susceptible to possible effects of high levels of manganese exposure because they absorb and/or retain more manganese than adults (ATSDR, 2012).

Attention to the potential health concerns of high levels of manganese in drinking water is appropriate, as the 0.5-mg/L notification level provides, given the possibility of neurologic effects at very high concentrations. 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 health guideline level of 0.4 mg/L (WHO, 2004).

Drinking Water Notification Level for Manganese

The current notification level for manganese is 0.5 milligram per liter (0.5 mg/L). When manganese is present in water served to customers at concentrations greater than the notification level, certain requirements and recommendations apply, as described below.

The notification level applies to all public water systems, regardless of being covered by the current regulation of manganese.

A health-based notification level for manganese is helpful in addressing high manganese levels in drinking water sources, in several ways:

  • It provides guidance and information to systems with manganese above the secondary MCL, as they deal with the regulatory requirements associated with exceeding the secondary standard (PDF), such as addressing costs associated with treatment.
  • It provides guidance to DDW staff in evaluating waivers from treatment requirements to meet the secondary MCL. Currently, consumers are to be surveyed about their acceptance of exceeding a secondary MCL. A notification level allows health-based considerations to enter into the consumer survey and waiver from treatment process.
  • It allows consumers of water from NTNC systems to be informed about the potential for health concerns associated with sources that have high levels of manganese.

When manganese is present in concentrations greater than the notification level, the following requirements and recommendations apply:

  • Systems with drinking water sources with manganese concentrations greater than the notification level are required to notify local city and county governing bodies, just as for other contaminants with notification levels and for contaminants that exceed MCLs.
  • Consumer notification is recommended at levels greater than the notification level. This may be handled through the water systems' annual consumer confidence reports. Other means could be used as well, if more appropriate, such as direct mailing, or posting a notice. These should be coordinated with the local DDW district office.
  • Source removal is recommended at ten times the notification level.

Monitoring for manganese is required within the framework of secondary MCL regulations, but generally not outside that framework. For sources not subject to the secondary MCL requirements, DDW recommends analyses of sources that are near other sources that have very high manganese levels.

For community systems subject to the secondary MCL monitoring and compliance requirements (22 CCR §64449) with manganese greater than the notification level, DDW recommends that information about the health concerns associated with high manganese exposures be provided to consumers as part of the required consumer dissatisfaction determination.

Current Regulation of Manganese

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.

Manganese Average Source Concentrations in 2020

Map on left shows average manganese source concentrations in 2020. Map on right shows median treated effluent manganese concentrations in 2020 entering the distribution system for sources with active manganese treatment.

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

Manganese Source Occurrences – Interactive Map (Tableau)

References

Other Information


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State Water Resources Control Board
Division of Drinking Water
Regulatory Development Unit

Mailing Address:
P.O. Box 100
Sacramento, CA 95812-0100

Street Address:
1001 I Street
Sacramento, CA 95814

E-mail us at DDWRegUnit@waterboards.ca.gov.