Is ambient air pollution a risk factor for Parkinson's disease? A meta-analysis of epidemiological evidence

Current evidence shows inconsistencies about ambient air pollution (AAP) exposure as a risk factor for Parkinson’s disease (PD). We performed meta-analyses to estimate the pooled risk of PD due to AAP exposure. We performed a systematic search in PubMed, Google Scholar, The Cochrane Library, and J-GATEPLUS databases for peer-reviewed epidemiological studies reporting the risk of PD due to exposure to PM2.5, PM10, O3, CO, NO2, NOX and SO2; from the beginning until October 2021. The pooled odds ratio (OR) for the effect of NO2 (per 1 μg/m3) and O3 (per 1 ppb) on PD was 1.01[95% CI: 1.00,1.02; I2 = 69% (p = .01)] and 1.01 [95% CI: 1.00,1.02; I2 = 66% (p = .03)], respectively. The ORs for the effects of PM2.5 (per 1 µg/m3) and CO (per 1 ppm) on PD were 1.01 [95% CI: .99,1.03; I2 = 40%] and 1.64 [95% CI: .96,2.78; I2 = 75% (p = .01)], respectively. The study showed the adverse roles of NO2, O3, PM2.5, and CO in increasing the risk for PD.