Manganese compounds used by potters are inorganic, like manganese dioxide, oxide and manganese carbonate; they do not penetrate the body via the skin as compared to some organic compounds. Metallic applications account for most manganese consumption, with about 90% used in steelmaking. Manganese is an essential mineral for humans and animals. It is necessary for normal bone formation. It has been estimated that a normal 70-kg man has a total of 12mg to 20 mg in his body.
Inhalation of dust or fume is the major route of entry in occupational manganese poisonning. Also inhaled large particles are ingested after mucociliary clearance from the lungs. Gastrointestinal absorption is generally low (10%). Very few poisonings have occured after ingestion. Tricarbonyls (organic) of manganese can be absorbed by the skin.
The primary target organs of manganese toxicity are the brain and the lungs.
- Neurological symptoms (chronic manganese poisoning) are caused by inhalation of fumes or dusts of manganese. Exposure to heavy concentrations of dusts or fumes for as little as three months may produce the condition, but usually cases develop after 1-3 years of exposure. The symptoms may simulate progressive bulbar paralysis, postencephalitic Parkinsonism, multiple sclerosis, amyotrophic lateral sclerosis(Lou Gerhig’s disease) and progressive lenticular degeneration(Wilson’s disease).
- Toxicity to the lungs is manifested as increased susceptibility to bronchitis or, in more severe cases, manganic pneumonia.
According to Robert R. Lauwerys ( probably the best occupational toxicologist in the world) in ‘Toxicologie Industrielle et Intoxications Professionnelles, 1999’, the best way to diagnose, at an early stage, manganese intoxication is neurological examination. A standardized questionnaire of neurological symptoms is helpful. Workers exposed to manganese should have a medical examination every 3 to 6 months (Shunk; Tanaka et Lieben).
Experts still differ about the precision of urinary and/or blood measurements of manganese as good indicators of exposure and intoxication. Among workers kept away from their job on a temporary basis, and from exposure to manganese dioxide, a good correlation was observed between urinary and blood levels and the index of cumulative exposure, on an individual basis (Lucchini and al.). A correlation was also found between these tests and different neurobehavioral tests. But let us not forget that human data are insufficient for proposing a a blood standard for manganese. Best thing to do is to treat a patient not a lab test (an old saying in medicine).
I have heard of 2 cases of Parkinson -like syndrome among unskilled workers making clays and glazes for a local pottery supplies store (Montreal) that happened in the 70’s or 80’s before Quebec passed its laws in Occupational Health and Safety. I was personnally involved in this process. The important thing is your exposure to inorganic manganese, it may vary if you are a pottery factory worker, a teacher, a full-time studio potter or a part-time. It certainly depends also on the amount used over a given period of time in clays and glazes. In the wet state, as in moist clays and glazes, these compounds are certainly much less hazardous than as dust. Factories can afford the monitoring of manganese exposure but it is not the same for artists and craftpersons.
So good house keeping of your studio is important. Avoidance of processes generating unnecessary dust is also important and the wearing of an approved dust mask when the exposure seems hazardous.
- Occupational Medicine, Carl Zenz, last edition.
- Occupational & Environmental Medicine, Joseph LaDou, last edition.
- Chemical Hazards of the Workplace, Proctor & Hughes, last edition.
- Industrial Chemical Exposure, Lauwerys & Hoet, last edition.
Many thanks to Edouard Bastarache for this further contribution to ceramic toxicolgy.