Critical windows of perinatal particulate matter (PM) exposure and preadolescent kidney function.

Air pollution exposure, especially particulate matter ≤2.5 μm in diameter (PM), is associated with poorer kidney function in adults and children. Perinatal exposure may occur during susceptible periods of nephron development. We used distributed lag nonlinear models (DLNMs) to examine time-varying associations between early life daily PM exposure (periconceptional through age 8 years) and kidney parameters in preadolescent children aged 8-10 years. Participants included 427 mother-child dyads enrolled in the PROGRESS birth cohort study based in Mexico City. Daily PM exposure was estimated at each participant's residence using a validated satellite-based spatio-temporal model. Kidney function parameters included estimated glomerular filtration rate (eGFR), serum cystatin C, and blood urea nitrogen (BUN). Models were adjusted for child's age, sex and body mass index (BMI) z-score, as well as maternal education, indoor smoking report and seasonality (prenatal models were additionally adjusted for average first year of life PM exposure). We also tested for sex-specific effects. Average perinatal PM was 22.7 μg/m and ranged 16.4-29.3 μg/m. Early pregnancy PM exposures were associated with higher eGFR in preadolescence. Specifically, we found that PM exposure between weeks 1-18 of gestation was associated with increased preadolescent eGFR, whereas exposure in the first 14 months of life after birth were associated with decreased eGFR. Specifically, a 5 μg/m increase in PM during the detected prenatal window was associated with a cumulative increase in eGFR of 4.44 mL/min/1.73 (95%CI: 1.37, 7.52), and during the postnatal window we report a cumulative eGFR decrease of -10.36 mL/min/1.73 (95%CI: -17.68, -3.04). We identified perinatal windows of susceptibility to PM exposure with preadolescent kidney function parameters. Follow-up investigating PM exposure with peripubertal kidney function trajectories and risk of kidney disease in adulthood will be critical.