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.

Background: Many low- and middle-income countries are experiencing high and increasing exposure to ambient fine particulate air pollution (PM _2.5). The effect of PM _2.5 on infant and child mortality is usually modelled using concentration response curves extrapolated from studies conducted in settings with low ambient air pollution, which may not capture its full effect. Methods: We pool data on more than half a million births from 69 nationally representative Demographic and Health Surveys that were conducted in 43 low- and middle-income countries between 1998 and 2014, and we calculate early-life exposure (exposure in utero and post partum) to ambient PM _2.5 using high-resolution calibrated satellite data matched to the child's place of residence. We estimate the association between the log of early-life PM _2.5 exposure, both overall and separated by type, and the odds of neonatal and infant mortality, adjusting for child-level, parent-level and household-level characteristics. Results: We find little evidence that early-life exposure to overall PM _2.5 is associated with higher odds of mortality relative to low exposure to PM _2.5. However, about half of PM _2.5 is naturally occurring dust and sea-salt whereas half is from other sources, comprising mainly carbon-based compounds, which are mostly due to human activity. We find a very strong association between exposure to carbonaceous PM _2.5 and infant mortality, particularly neonatal mortality, i.e. mortality in the first 28 days after birth. We estimate that, at the mean level of exposure in the sample to carbonaceous PM _2.5 - 10.9 μg/m ³ - the odds of neonatal mortality are over 50% higher than in the absence of pollution. Conclusion: Our results suggest that the current World Health Organization guideline of limiting the overall ambient PM _2.5 level to less than 10 μg/m should be augmented with a lower limit for harmful carbonaceous PM _2.5.

Pregnant mothers in Bangladesh are exposed to very high and worsening levels of ambient air pollution. Maternal exposure to fine particulate matter has been associated with low birth weight at much lower levels of exposure, leading us to suspect the potentially large effects of air pollution on stunting in children in Bangladesh. We estimate the relationship between exposure to air pollution in utero and child stunting by pooling outcome data from four waves of the nationally representative Bangladesh Demographic and Health Survey conducted between 2004 and 2014, and calculating children’s exposure to ambient fine particulate matter in utero using high resolution satellite data. We find significant increases in the relative risk of child stunting, wasting, and underweight with higher levels of in utero exposure to air pollution, after controlling for other factors that have been found to contribute to child anthropometric failure. We estimate the relative risk of stunting in the second, third, and fourth quartiles of exposure as 1.074 (95% confidence interval: 1.014-1.138), 1.150 (95% confidence interval: 1.069-1.237, and 1.132 (95% confidence interval: 1.031-1.243), respectively. Over half of all children in Bangladesh in our sample were exposed to an annual ambient fine particulate matter level in excess of 46 μg/m³, these children had a relative risk of stunting over 1.13 times that of children in the lowest quartile of exposure. Reducing air pollution in Bangladesh could significantly contribute to the Sustainable Development Goal of reducing child stunting.