The association of in-utero exposure to ambient fine particulate air pollution with low birth weight in India

A growing body of research indicates that in-utero exposure to ambient fine particulate matter (PM2.5) is a risk factor for low birth weight (LBW). However, research on India, where the high and rising level of ambient air pollution is a significant health concern, is limited. In this study, we analyze the association between ambient PM2.5 and LBW in India. We match data on birth weight from the National Family and Health Survey (NFHS) conducted in India in 2015-16 with high-resolution spatial data on annual ambient PM2.5 concentration to calculate in-utero exposure based on the residential location of each child. We estimate the association of in-utero exposure to ambient PM2.5 with birth weight and LBW, after adjusting for child level, maternal, and household level characteristics that predict birth weight. In our sample (n = 149 416), in comparison to the reference category of in-utero PM2.5 level less than 26.7 µg m-3, the adjusted OR of LBW increases non-linearly from 1.098 (95% CI: 0.954, 1.263) for children in the exposure band 39.3-44.7 µg m-3 (i.e., the fourth octile) to 1.241 (95% CI: 1.065, 1.447) for those in the exposure band 44.7-51.6 µg m-3 (i.e., the fifth octile) and 1.405 (95% CI: 1.126,1.753) for those with in-utero PM2.5 level greater than 77.3 µg m-3 (i.e., the last octile). Our findings show that exposure to ambient PM2.5 is strongly associated with LBW in India and suggest that policies that improve air quality may be necessary for achieving the World Health Assembly target of 30% reduction in LBW by 2025.