March 29, 2022, the State Water Resources Control Board (SWRCB) Division of Drinking Water (DDW) sent out a brief notice stating that DDW “….has initiated the process of developing revised notification and response levels for manganese. This process will result in proposed new notification level and response level concentrations for manganese.” At the present time no additional details are available.
The current Notification Level (NL) for manganese is 0.5 mg/L (the Response Level is 10 times the Notification Level).
Manganese also has a secondary Maximum Contaminant Level (MCL) of 0.05 mg/L.
Link to DDW web page with background information on manganese: