Researchers using a rodent model of childhood manganese exposure have found that too much manganese early in development causes lasting attention deficits and other impairments. Manganese is an essential element, required by the body in trace amounts...The most common source of exposure to excess manganese is drinking water from wells, because groundwater in some areas is naturally high in manganese. Soy-based infant formulas also have much higher levels of manganese than breast milk.