Objective:

To assess the relationship between environmental exposure to airborne metals and Parkinson disease (PD) risk.

Background:

Several heavy metals are neurotoxic and biologically plausible risk factors for PD.

Design/Methods:

In the Multiple Air Pollutants in PD (MAP-PD) study, a population-based case-control study using Medicare data, we examined PD risk in relation to 11 airborne metals at the residential 9-digit zip code two years before diagnosis/selection in 2009 (51,991 incident cases and 13,177,274 controls with complete metals data). We obtained census tract-level estimates for air concentrations of antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium from all sources as modeled by the EPA. We used logistic regression to estimate the relative risk (RR) of PD in relation to each metal, adjusting for age, sex, race, smoking, and healthcare utilization. We also examined the effect of adjustment for other metals, diesel and fine particulate matter, and trichloroethylene.

Results:

Most metals were positively associated with PD in the demographics-adjusted model, but only manganese remained significant in all sensitivity analyses. With adjustment for particulate matter, the RR of PD in relation to manganese was 1.007 (95% CI: 1.001-1.012) greater for each standard deviation increase in exposure. We found a possible association between PD and beryllium (RR=1.008, 95% CI: 0.999-1.017) and nickel (RR=1.006, 95% CI: 0.997-1.014) of similar magnitude. The associations for manganese and nickel were linear with markedly greater RR for PD at the highest manganese exposure levels. The association for manganese was significant for most sources: major point sources (RR=1.006, 95% CI: 1.001-1.012), area non-point sources (RR=1.009, 95% CI: 1.001-1.016), and on road mobile sources (RR=1.011, 95% CI: 1.0001-1.022) for each standard deviation increase in exposure.

Conclusions:

Residential exposure to airborne manganese, and possibly beryllium and nickel, might increase risk of PD.