06/03/2026
California State Water Resources Control Board (SWRCB)
Revised Drinking Water Notification and Response Levels for Manganese
On June 2, 2026, under the authority of the Deputy Director of the State Water Board’s Division of Drinking Water (Division), California issued revised notification and response levels for manganese.
The current notification and response levels for manganese are:
Notification Level: 0.05 milligrams per liter (mg/L) (Based on a running annual average)
Response Level: 0.20 milligrams per liter (mg/L) (Based on a single confirmed detection)
As the first step in establishing a manganese primary maximum contaminant level, the Division has requested the Office of Environmental Health Hazard Assessment establish a manganese Public Health Goal.
Background
Manganese is an essential nutrient and enzyme cofactor that is naturally present in many foods and available as a dietary supplement. Despite its nutritional benefits, adverse health effects can be caused by over-exposure. Formula-fed infants may be particularly susceptible to adverse neurotoxicological effects from manganese exposure because they absorb and retain more manganese than adults. Public health notification and related mitigation can protect formula-fed infants by notifying parents and caregivers that short periods of manganese exposure above the response level may lead to developmental impacts.
Notification and response levels are non-regulatory, health-based advisory levels established for contaminants in drinking water for which maximum contaminant levels have not been established.
Public Water System Notification Requirements
Within 30 days after a public water system learns of a confirmed detection exceeding a maximum contaminant level, notification and/or response level, the public water system must notify its governing body of the exceedance(s) and any relevant governing bodies of the areas it serves (Health and Safety Code section 116455).
Health and Safety Code section 116450, subdivision (e) authorizes the Division to require a public water system to notify its customers to avoid internal consumption of the water supply and use bottled water due to a chemical contamination problem that may pose a health risk. Health and Safety Code section 116450, subdivision (g), further requires certain customers (such as schools, rental properties, and businesses) to provide the same notice to those consuming the water.
The Division considers the exceedance of the manganese response level to pose a potential health risk to formula-fed infants and recommends notifying customers to use an alternative water supply (bottled water) when preparing formula for infants. Accordingly, pursuant to Health and Safety Code section 116450, to reduce public exposure following a confirmed response level exceedance a community water system must notify customers to use an alternative water supply (bottled water) when preparing formula for infants, or mitigate the exposure until exceedances cease (take source offline, provide treatment or provision of alternative water).
The Division may require the same notice as described in the paragraph above for non-community water systems that serve a vulnerable population, as determined on a case-by-case basis.
Community Water System Monitoring Requirements
Water systems must confirm their monitoring schedules are current and compliant. Specifically, community systems must test groundwater every three years and conduct quarterly monitoring if manganese exceeds the secondary maximum contaminant level. The Division is actively reviewing compliance. Contact District Office with any questions.
Funding for Manganese
See link below to Manganese Frequently Asked Questions
Additional information is available on the Division’s websites:
Notification Levels:
https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/NotificationLevels.html
Manganese Revised Notification and Response Level Issuance Document:
https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/docs/2026/manganese-nl-issuance-2026.pdf
Manganese:
https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/Manganese.html
Manganese Frequently Asked Questions:
https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/docs/2026/mn-faq.pdf
