Clinical Information

Manganese (Mn) is an essential trace element with many industrial uses. Mn is the 12th most abundant element in the earth's crust and is used predominantly in the production of steel. These industrial processes cause elevated environmental exposures to airborne Mn dust and fumes, which in turn have led to well-documented cases of neurotoxicity among exposed workers. Mining as well as iron and steel production have been implicated as sources of exposure.

Inhalation is the primary source of entry for Mn toxicity. Signs of toxicity may appear quickly or not at all; neurological symptoms are rarely reversible. Mn toxicity is generally recognized to progress through 3 stages. Levy describes these stages. "The first stage is a prodrome of malaise, somnolence, apathy, emotional lability, sexual dysfunction, weakness, lethargy, anorexia, and headaches. If there is continued exposure, progression to a second stage may occur, with psychological disturbances, including impaired memory and judgment, anxiety, and sometimes psychotic manifestations such as hallucinations. The third stage consists of progressive bradykinesia, dysarthria, axial and extremity dystonia, paresis, gait disturbances, cogwheel rigidity, intention tremor, impaired coordination, and a mask-like face. Many of those affected may be permanently and completely disabled."(1)

 

Few cases of Mn deficiency or toxicity due to ingestion have been documented. Only 1% to 3% Mn is absorbed via ingestion, while most of the remaining Mn is excreted in the feces. As listed in the United States National Agriculture Library, Mn adequate intake is 1.6 to 2.3 mg/day for adults. This level of intake is easily achieved without supplementation by a diverse diet including fruits and vegetables, which have higher amounts of Mn than other food types. Patients on a long-term parenteral nutrition should receive Mn supplementation and should be monitored to ensure that circulatory levels of Mn are appropriate.