Manganese in Minnesota's Groundwaters Emphasizing the Health Risks of Manganese in Drinking Water

Manganese is a naturally-occurring element in the groundwater that is well known for causing aesthetic problems with drinking water. Much of Minnesota's soil, bedrock, and groundwater commonly contains manganese. Water professionals recognize that water supplies containing more than ~50 micrograms per liter (ug/L) dissolved manganese can be a household nuisance because atmospheric oxygen causes manganese in these water supplies to precipitate in water mains, leading to stained laundry and fixtures, and distinct aesthetic effects such as discoloration, odor, or taste (Figure 1). More than 60% of ambient groundwater measurements in Minnesota exceed 50 ug/L, suggesting that many water supplies contain excess manganese. There is increasing recognition of human health effects caused by manganese. Acute neurological effects resulting from inhalation of manganese have long been recognized, and recent studies indicate that ingestion of excess manganese also poses a potential health risk. These studies demonstrate that although manganese is essential for body functions, subtle decreases in memory, attention, and motor skills are positively correlated with drinking water manganese concentrations, especially above 100 ug/L (Figure 2). Infants relying on powdered formula mixed with drinking water containing high levels of manganese are at highest risk; they are unable to excrete excess manganese and they absorb ingested manganese more readily than adults and children.