In occupational exposure, manganese is absorbed mainly through inhalation, but may also enter the gastrointestinal tract with contaminated food and water. If entering the body in sufficient quantities, this can lead to manganese poisoning, with its nervous disorders and possible disfiguration of the joints.
Intoxication by manganese is reported among workers in the mining and processing of manganese ores, and in the production of manganese alloys, dry cell batteries, welding electrodes, varnishes, and ceramic tiles. Mining of ore is still the major occupational hazard, with the ferromanganese industry as the next most important source of risk. The operations that produce the highest concentrations of manganese dioxide dust are those of drilling and shotfiring. Consequently, the most dangerous job is high-speed drilling.