High prevalence of parkinsonian disorders associated to manganese exposure in the vicinities of ferroalloy industries

Objective To assess the prevalence of Parkinsonian disturbances in relationship to environmental exposure to manganese due to ferroalloy industries in the province of Brescia, Northern Italy. Methods Manganese concentrations were measured in settled dust collected in each of the 206 municipalities. Parkinsonian patients were identified using two sources: (1) clinical registers from local hospitals, specialized neurologists, and exemption from prescription payment; (2) L‐Dopa prescriptions. Standardized prevalence rates and raw and full Bayesian‐smoothed standardized morbidity ratios (SMRs) were calculated for the entire province and for each municipality. Results Manganese concentrations in settled dust were significantly higher in the surroundings and downwind from the industrial plants. A total number of 2,677 Parkinsonian cases were identified among 903,997 residents (crude prevalence, 296/100,000; 95% CI: 284.80–307.20; standardized prevalence, 407/100,000; 95% CI: 393.87–420.12). Significantly higher SMRs (Kruskal–Wallis χ2 1 df = 17.55, P