Manganese: A Blessing for Stainless Steel, But a Curse for Welders?

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Metals bring us many wonderful technologies and undoubtedly improve our quality of life but, occasionally, some can have previously unknown or unexpected side effects. One of those is low-level exposure to manganese, if research by Brad Racette, a neurologist at Washington University in St Louis, as reported in the Economist, proves correct.

Manganese ore is an ingredient in stainless steel as a treatment that prevents rust and corrosion.

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As the article points out, it’s been known for more than a hundred years that manganese-bearing ores carry risks to miners exposed to high levels of dust. The condition called Manganism causes slurred speech, loss of motor control and eventually psychosis and death. Recent research, though, has been aimed at workers exposed to low levels of manganese, such as welders who inhale it as welding fumes from manganese-bearing steels.

Possible Link to Parkinson’s Disease

Researchers found that symptoms resembling Parkinson’s disease (PD) were 15% more prevalent in welders than in other kinds of workers. In another, they found that in a small sample of welders who had not yet reported any neurological symptoms, brain scans showed signs of damage to a part of their brains called the striatum that coordinates movement and that gets damaged by Parkinson’s Disease.

In the case of Parkinson’s, it has been clearly shown that the first symptoms appear only after the striatum has lost more than half of its neurons. The article readily makes the point that these findings are controversial, not least of which is because the link to Parkinson’s is not proven yet by the research, but it suggests there could possibly be a causal link.

What is Known to Date

What IS clear is that high levels of manganese are not good for the brain and, more seriously, what constitutes a “high level of exposure” may need to be reappraised. The article states that as a trace element in people’s diet, manganese is essential to keeping organs, including the brain, healthy. The American standard for the airborne concentration of manganese dust is now 5 milligrams per cubic meter of air—a vast improvement on the doses of close to 1,000mg/m3 that some workers were exposed to only 60 years ago.

Last year, Robert Park, a statistician with the US-based National Institute for Occupational Safety and Health, published a review that concluded there was strong evidence of neurological effects at concentrations lower than 0.2mg/m3. Clearly this vital research should be heeded and expanded upon.

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