Toxic effects of manganese Manganese is a metal with a relatively low acute toxicity, but many adverse effects from prolonged excess exposure [1]. The brain is the primary target of its toxicity, but the lung, the cardiovascular and the endocrine systems are also affected. In addition, excess manganese has immunological, genotoxic and carcinogenic effects.
Manganese and iron are thought to share absorptive and metabolic pathways. Manganese can interfere with the absorption of dietary iron and long-term exposure to excess levels may result in iron-deficiency anemia. This can be one of the effects of industrial pollution, with workers in the manganese processing industry most at risk. Manganese poisoning has been found among workers making batteries. Symptoms of toxicity also mimic those of Parkinson's disease (tremors, stiff muscles) with hypertension in subjects older than 40 years. In this respect the toxicant effect of manganese is thought to be related to depletion of brain dopamine, with a syndrome of motor dysfunction and memory loss resembling Parkinson disease [12].
While excess manganese exposure can produce neurological symptoms similar to those of Parkinson’s disease, there are important differences between the two conditions: for example, Parkinson’s is associated with a persistent, resting tremor, whereas manganism is associated with an intentional or kinetic tremor. Blood pressure is also significantly higher in chronic manganese exposure than in Parkinson’s and there are other pathological differences between the two conditions [13]. However, exposure to excess manganese (or copper) is thought to increase the risk of developing Parkinson’s disease [14]
The carbamate pesticide “Mancozeb” is a wide spectrum anti-fungal containing manganese which may significantly increase the Mn content of ingested fruit and field crops [1]. Reported symptoms of human direct exposure to Mancozeb include skin rash, fatigue, headache, blurred vision and nausea [15].
Environmental exposure to airborne manganese has been associated with neurobehavioral deficits in adults and in children [16,17]. In exposed workers, neurobehavioral deficits have been shown to correlate with manganese deposition in the brain observed by magnetic resonance imaging [3].