Jean Rodier: History of Manganism in Morocco.

Jean Rodier (1920-2003), distinguished researcher and scientist, directed the Toxicology Department of Hygiene Institute of Rabat under the French Protectorate. From 1946, he developed numerous lines of research in occupational health, in particular on Manganism, a neurological disorder that impacted miners in his home country of Morocco. His many papers on Manganism, only one of which was published in English, describe field and laboratory research studies that focused its prevention and management.

The early history of manganese and the recognition of its neurotoxicity, 1837-1936.

The history of the biomedical recognition manganese-caused neurotoxicity mirrors changing technologies as much as it does the ontology of parkinsonism. The initial 1837 report of manganese-induced neurologic injury was made by John Couper, a university-based physician in Scotland. He made clear that the outbreak occurred among workers at the Charles Tennant bleach manufactory in the environs of Glasgow. The relatively new technology of chlorine generation using manganese accounted for the novel exposure involved. At the time, this factory was the largest hypochlorite bleaching powder producer in the world. As the 19th century progressed, technological change in steel fabrication requiring higher manganese content greatly increased demand for the metal. Nonetheless, more than six decades elapsed before the next reports of manganese neurotoxicity emerged. Two unrelated outbreaks (both on Continental Europe) were reported within weeks of each other in 1901, one by von Jaksch and the other by Embden. All the cases were heavily exposed to manganese-containing dust. By the eve of the First World War, a total of 9 patients with manganese-caused neurologic illness had been reported in five separate Continental European publications. Meanwhile, new technology led to another exposure source. Magnetic separation techniques allowed the extraction of zinc from mixed ore also containing iron and manganese, leading to exploitation of a unique source of high manganese-content ore found in New Jersey. Not long after that technology's introduction, in 1912 Casamajor reported the first U.S. cases of manganism, detailing classic findings. Additional cases from the same cohort were reported a few years later, with continued exposure driven by First World War-driven demand for manganese to be used in armaments. The nosology of chronic manganese neurotoxicity remained in flux, with considerable emphasis on shared attributes with Wilson's disease, a syndrome only then recently described. A landmark 1924 primate study by Mella showed manganese-induced basal ganglion damage; human autopsy study data in the years following further supported the view that manganese toxicity represented a parkinsonian syndrome. As the 1937 centenary of Couper's first report approached, newer technologies (electric arc welding and battery making) were being linked to manganese-caused disease, even as mineral extraction was expanding as a global source of exposure.

Original footage of the Chilean miners with manganism published in Neurology in 1967.

Manganism has captured the imagination of neurologists for more than a century because of its similarities to Parkinson disease and its indirect but seminal role in the "l-dopa miracle." We present unpublished footage of the original case series reported in Neurology® in 1967 by Mena and Cotzias depicting the typical neurologic signs of manganism in 4 Chilean miners and their response to high doses of l-dopa.

State-of-the-science review: Does manganese exposure during welding pose a neurological risk?

Recent studies report that exposure to manganese (Mn), an essential component of welding electrodes and some steels, results in neurotoxicity and/or Parkinson's disease (PD) in welders. This "state-of-the-science" review presents a critical analysis of the published studies that were conducted on a variety of Mn-exposed occupational cohorts during the last 100 yr, as well as the regulatory history of Mn and welding fumes. Welders often perform a variety of different tasks with varying degrees of duration and ventilation, and hence, to accurately assess Mn exposures that occurred in occupational settings, some specific information on the historical work patterns of welders is desirable. This review includes a discussion of the types of exposures that occur during the welding process--for which limited information relating airborne Mn levels with specific welding activities exists--and the human health studies evaluating neurological effects in welders and other Mn-exposed cohorts, including miners, millers, and battery workers. Findings and implications of studies specifically conducted to evaluate neurobehavioral effects and the prevalence of PD in welders are also discussed. Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., "manganism") in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity. The available data might support the development of reasonable "worst-case" exposure estimates for most welding activities, and suggest that exposure simulation studies would significantly refine such estimates. Our review ends with a discussion of the data gaps and areas for future research.

Manganese intoxication.

Manganese plays an important role as a cofactor in many enzymatic reactions in humans but in excess amounts can cause irreversible nervous system damage. Although manganism is a rare condition, it can be the cause of complex nervous system symptoms, especially in the setting of environmental exposure. Specifically, manganese is a well-known cause of dystonic parkinsonism. This article highlights several historical descriptions of the clinical manifestations, pathological changes, and attempted therapeutic intervention in manganese intoxication.