Manganese & compounds: Health effects
Description
Manganese is an essential element for humans, in fact for all living organisms including animals, plants and bacteria. Its naturally occurring concentrations are hardly toxic and relatively large doses can be tolerated without adverse effects. It is found in all human tissues, with the highest manganese concentrations in the liver, pancreas, intestinal tract and kidneys. Food is the major natural source of manganese intake and the amount of manganese in a normal diet is enough to meet daily needs with no ill health effects. Its absorption can be influenced by dietary level of manganese and iron, the type of manganese compound, iron deficiency and age. Occupational exposure to manganese can be substantial. In its acute form, manganese poisoning has an effect characteristic of other heavy metals, leading to 'metal fume fever' if dust or fume is inhaled in sufficient quantity. An airborne concentration thought to be immediately dangerous to life or health is in the order of 10,000 milligram/m3. Chronic exposure to manganese can express itself in two major ways, namely bronchitis/pneumonitis after inhalation of manganese dust, and 'manganism'. Manganism may also result from inhalation. However, the airborne manganese concentration which gives rise to these effects is different. Manganism is the effect of chronic manganese poisoning. This disease, which arises from damage to the central nervous system (CNS), usually begins with psychological symptoms such as hallucinations, emotional instability and disturbances in behaviour. These may be followed by neurological symptoms such as muscular weakness, speech disturbances and headaches, as well as symptoms resembling those of Parkinson's disease (tremors, stiffness, motor dysfunction). If exposure is terminated soon after the neurological symptoms appear, the individual generally recovers, but some speech and balance problems may remain. Individual susceptibility to the adverse effects of manganese varies considerably. The minimum dose that produces effects on the CNS is not known, but signs of adverse effects may occur at manganese concentrations ranging from 2 to 5 milligram/m3 in air. Deficiencies in the diet may predispose workers to anaemia, thus increasing susceptibility to manganese. An increased incidence of pneumonia has been reported among individuals exposed to manganese. A common effect in men who are exposed to high levels of manganese dust in air is impotence.
Entering the body
Manganese can be inhaled or ingested. Absorption of inorganic manganese through the skin appears to be negligible. However, with organo-manganese compounds there can be significant absorption through the skin.
Exposure
Most exposure will be associated with drinking water and consuming foods containing manganese. Exposure to manganese and its compounds may also occur during mining and processing of the ore, manganese smelting, ferrous and non-ferrous alloying, welding/brazing processes (either from electrodes/rods or parent material), battery (dry cell and alkaline) manufacture, and production and use of manganese chemicals and fertilisers, for those involved in these industries.
Health guidelines
Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996):
Health: Maximum of 0.5 mg/L (i.e. 0.0005 g/L)
Aesthetic: Maximum of 0.1 mg/L (i.e. 0.0001 g/L)
Worksafe Australia has set the exposure standard for manganese dust, fume, and compounds (as manganese) to 1 mg/m3 (TWA). The recommended short term exposure level (STEL) for manganese fume should not exceed 3 mg/m3.
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