Interrelationship of residential greenness and traffic-related air pollution with kidney function in adults

Residential greenness has been associated with improved renal function, whereas traffic-related air pollutants such as PM 2 . 5 and NO 2 have been linked to declines in renal function. However, their interrelationship remains unclear. This study examined whether PM 2 . 5 and NO 2 mediate the association between greenness and renal function. We combined the nationwide dataset of the Taiwan Biobank between 2008 and 2020 with the information on residential greenness and air pollutant exposures based on township levels of each participant’s residential address. A total of 113 164 eligible adults, aged 30–70 years, were included in the analysis. Renal function was evaluated using the Taiwan-specific estimated glomerular filtration rate (eGFR_Taiwan) while exposure variables included residential greenness, quantified using the normalized difference vegetation index (NDVI), and concentrations of PM 2.5 and NO 2 , estimated through land-use regression models employing machine learning techniques. Multiple regression and causal mediation analyses were applied. Higher NDVI was significantly associated with increased eGFR_Taiwan (estimate = 0.17, p < 0.0001). Conversely, PM 2 . 5 and NO 2 exposures were linked to reduced eGFR_Taiwan (estimates = −0.17 and −0.15, p < 0.0001 and p < 0.001, respectively). PM 2 . 5 partially mediated the NDVI-eGFR_Taiwan association, accounting for 30.8% of the total effect. Beyond its direct association with renal function, residential greenness has also been associated with better renal health, potentially through the reduction in ambient concentrations of PM 2 . 5 .