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 chi(2) 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.