New USGS Study Finds Elevated Levels of Manganese in Private Wells

A new USGS study reports that about 7 percent of domestic (private) wells in the U.S. have concentrations of manganese at levels that present a potential human health risk. These wells provide drinking water for an estimated 2.6 million people.

The study found that elevated levels of manganese occur frequently in groundwater near rivers, where the water level is shallow, where the organic carbon levels in soil are high, or where nitrogen fertilizer has been liberally used. Areas with elevated levels of manganese in groundwater were concentrated along the Mississippi valley, the eastern coast up to Maine, and the Great Lakes area. All of these features can be mapped and Graphical Information Systems (GIS) are coming down in price, which helps local governments with mapping. These maps could be useful in determining where water wells should be drilled to avoid high concentrations of manganese.

For community water systems, manganese has been recognized with a secondary Maximum Contaminant Level (SMCL) of 50 micrograms per liter. The interest in manganese has increased somewhat over the past few years as manganese is included in the ongoing monitoring under the Fourth Unregulated Contaminant Monitoring Rule (UCMR), which continues until the end of 2020. The UCMR4 reporting limit is 0.4 micrograms per liter.