Robust relationship between ambient air pollution and infant mortality in India

Ambient exposure to fine particulate matter (PM_2.5) is one of the top global health concerns. We estimate the associations between in-utero and perinatal exposure to PM_2.5 and infant, neonatal and postneonatal mortality in India. We evaluate the sensitivity of this association to two widely-used exposure assessments.

We linked nationally representative anthropometric data from India's 2015-2016 Demographic and Health Survey (n = 259,627 children under five across 640 districts of India) with satellite-based PM_2.5 concentrations during the month of birth of each child. We then estimated the associations between PM_2.5 from each dataset and child mortality, after controlling for child, mother and household factors including trends in time and seasonality. We examined if factors: urban/rural, sex, wealth quintile and state modified the associations derived from the two datasets using Wald tests.

We found evidence that PM_2.5 impacts infant mortality primarily through neonatal mortality. The estimated association between neonatal mortality and PM_2.5 in trimester 3 was OR: 1.016 (95% CI: 1.003, 1.030) for every 10 μg/m³ increase in exposure. This association was robust to the exposure assessment used. Child sex was a significant effect modifier, with PM_2.5 impacting mortality in infant girls more than boys.

Our results revealed a robust association between ambient exposure to PM_2.5 in the latter period of pregnancy and early life with infant and neonatal mortality in India. Urgent air pollution management plans are needed to improve infant mortality in India.