Manganese is a mineral that naturally occurs in rocks and soil and is a normal constituent of the human diet. It exists in well water in Connecticut as a naturally occurring groundwater mineral, but may also be present due to underground pollution sources.
Manganese may become noticeable in tap water at concentrations greater than 0.05 milligrams per liter of water (mg/L) by imparting a color, odor, or taste to the water. However, health effects from manganese are not a concern until concentrations are approximately 10 times higher. The Connecticut Department of Public Health (DPH) recently set a drinking water Action Level (AL) for manganese of 0.5 mg/L to ensure protection against manganese toxicity. This AL is consistent with the World Health Organization guidance level for manganese in drinking water. The Connecticut AL provides guidance for prudent avoidance of manganese concentrations of potential health concern. Local health departments can use the AL in making safe drinking water determinations for new wells, while the homeowner in consultation with local health authorities makes decisions regarding manganese removal from existing wells.
This fact sheet is intended to help individuals who have manganese in their water understand the health risks and evaluate the need for obtaining a water treatment system.