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 < 0.001) were observed in 37 municipalities in the vicinities of ferromanganese plants (324 cases among 77,708 residents; standardized prevalence 492/100,000; 95% CI: 442.80-541.20), compared to the other 169 municipalities of the province (2,353 cases among 826,289 residents, standardized prevalence 321/100,000; 95% CI 308.80-333.20). Row and Bayesian SMRs were associated with the concentrations of manganese in settled dust. Conclusion: Study results suggest that environmental exposure to manganese is associated with an increased prevalence of Parkinsonian disturbances. Since the highest prevalence rates were observed in a closed community of the pre-Alps where the industries are located, further research should address a possible interactive role of genetic factors.