To investigate the relationship between air pollutant concentrations (µg/m³) and the dopaminergic system in patients with Parkinson’s disease (PD).

All data used in analyses were obtained from the Parkinson’s Progression Markers Initiative (PPMI) dataset. Average annual air pollutant concentrations from 2005–2018 were retrieved from the National Environmental Public Health Tracking Network () using participants' residential ZIP codes. A composite air toxicity score was created by averaging the total pollutants’ z-scores for both PD and HC groups. Spearman correlations assessed the relationship between composite air toxicity score and DaT-SPECT specific binding ratios while controlling for age. 

221 PD patients and 70 HCs with available DaT-SPECT and environmental data were included in the analysis across 40 states and 160 cities. In PD patients, significant negative correlations were found between the composite air toxicity score and DaT-SPECT in the putamen (r=-0.20,p<0.01) and a non-significant negative correlation in the caudate (r=-0.13, p=0.06). Benzene and 1,3-butadiene showed significant negative correlations with the putamen (r=-0.21, p<0.01; r=-0.17, p=0.01, respectively). In the caudate, only benzene had a significant negative correlation (r=-0.17, p=0.01), while 1,3-butadiene showed a non-significant trend (r=-0.12, p=0.08). Formaldehyde and acetaldehyde both showed non-significant negative associations with the putamen and caudate (p>0.05). No significant associations were observed in the HC group for any variables.