1:32 Last year, the Wisconsin Department of Natural Resources found elevated levels of manganese in public water supplies in counties across northern and western parts of the state. That includes Oneida, Iron and Marathon counties. Because of this, the Oneida County Health Department is encouraging Northwoods residents to get their well water tested. “The Oneida County health department just wants to make private well owners aware that there is a potential for manganese exceedances in their well,” Todd Troskey, an environmental health specialist with the health department, said. Manganese can cause discoloration in sinks, showers and toilets where water runs. But it doesn’t just affect appliances. It can also affect your health.