Manganese
Manganese intoxication generally is caused by chronic exposure. Sources of inorganic manganese exposure include mining, metal working, smelting, foundries, and welding. Recent studies also suggest a possible link between an organic manganese fungicide (Maneb) and chronic neurologic toxicity. An organic manganese gasoline additive, methylcyclopentadienyl manganese tricarbonyl (MMT), has not yet been introduced in the United States because of public health concerns but is used elsewhere. Finally, parenteral exposure to inorganic manganese has occurred through injection drug abuse of potassium permanganate–adulterated substances and through manganese-containing total parenteral nutrition.
Mechanism of toxicity. The precise mechanism is not known. The CNS is the target organ, specifically regions within the basal ganglia.
Toxic dose. The primary route of exposure is inhalation, but there is evidence that absorption to the CNS through the olfactory system may play a role in toxicity. IV injection also leads to effective delivery of this toxin. Metallic inorganic manganese is poorly absorbed from the GI tract; potassium permanganate ingestion, however, can cause systemic toxicity. MMT can be absorbed across the skin. The OSHA workplace limit (permissible exposure limit—ceiling [PEL-C]) for inorganic manganese is 5 mg/m3
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