Long Term Exposure to Ambient Particulate Matter _2.5 and Kidney Function in Urban Indian Adults

Despite epidemiological evidence linking fine particulate matter (PM_2.5) to cardiometabolic diseases, links between PM₂.₅ and kidney function or chronic kidney disease (CKD) remain inconclusive.

In a population representative cohort of 12,271 adults (age ≥ 20 years) in 2 Indian cities (Chennai and Delhi), we investigated time-varying associations between annual average ambient PM_2.5 and estimated glomerular filtration rates (eGFR) calculated using CKD-Epidemiology Collaboration (EPI) 2009 equations, at 3 time points during 2010 to 2016. Ambient PM_2.5 exposures were assessed at residential geocodes using a national high-resolution spatiotemporal model for daily PM_2.5 at 1 km × 1 km. City-specific linear mixed effect models were employed, incorporating inverse probability-based weighting to account for loss-to-follow-up. Effect modification by sex, waist-to-hip ratio, hypertension, and diabetes status were assessed using stratified models.

Annual average PM_2.5 at baseline and 2 follow-ups in Chennai were 33, 37, and 30 μg/m³ whereas those in Delhi were 118, 123, and 130 μg/m³. Median eGFRs at baseline were 112 ml/min per 1.73 m² (interquartile range [IQR]: 101.9-121.0) in Chennai and 106.4 ml/min per 1.73 m² (IQR: 94.4-116.6) in Delhi. Over time, a 5 ug/m³ increase in annual average PM_2.5 was associated with a significant decline in eGFR in both cities as follows: -0.32 (95% confidence interval [CI]: -0.49 to -0.15) ml/min per 1.73 m² in Chennai and -0.42 (95% CI: -0.57 to -0.27) ml/min per 1.73 m² in Delhi.

Annual average PM_2.5 levels were associated with declines in eGFR. These data from a relatively young South Asian urban cohort underscore the need to further investigate the potential renal and cardiovascular impacts of sustained air pollution exposure.