Child Survival and Early Lifetime Exposures to Ambient Fine Particulate Matter in India: A Retrospective Cohort Study

BACKGROUND: Ambient line particulate matter [PM <= 2.5 mu m in aerodynamic diameter (PM2,5)[is a major health risk for children, particularly in South Asia, which currently experiences the highest PM2,5 levels globally. Nevertheless, there is comparatively little epidemiological evidence from this region to quantify the effects of PM2.5 on child survival. OBJECTIVES: We estimated the association between PM2.5 exposure and child survival in India. METHODS: We constructed a large, retrospective, and nationally representative cohort of children <5 years of age, horn between 2009-2016, from the publicly available, cross-sectional 2015-2016 Demographic Health Surveys in India. In utero and post-delivery lifetime average ambient PM2,5 exposures were estimated with data from satellite remote sensing, meteorology, and land use information (model R-2 = 0.82). We used Cox proportional hazards regression to estimate the association between both average in utero and post-delivery lifetime PM2.5 and all-cause child mortality, controlling for individual- and household-level covariates, seasonality, location, and meteorology. RESULTS: Over 7,447,724 child-months of follow-up, there were 11,559 deaths at <5 years of age reported by the children's mothers. The mean concentrations of 9-month in utero and post-delivery lifetime average ambient PM2.5 exposure were 71.1 mu g/m(3) (range: 20.9-153.5 mu g/m(3)) and 73.7 mu g/m(3) (range: 14.0-247.3 mu g/m(3)), respectively. Estimated child mortality adjusted hazard ratios were 1.023 [95% confidence interval (CI): 1.008, LOA and 1.013 (9.5% CI: 1.001, 1.026) per 10-mu g/m(3) increase of in utero and post-delivery lifetime PM2.5, with both exposures in the model. DISCUSSION: This study adds to the growing body of evidence about the adverse health effects of PM2.5 by demonstrating the association between exposure, both in utero and post-delivery, on child survival at the national level in India. Strategies to reduce ambient air pollution levels, including steps to minimize in utero and early life exposures, are urgently needed in India and other countries where exposures arc above recommended guideline values.