The association of early-life exposure to ambient PM(2.5) and later-childhood height-for-age in India: an observational study

BACKGROUND: Children in India are exposed to high levels of ambient fine particulate matter (PM(2.5)). However, population-level evidence of associations with adverse health outcomes from within the country is limited. The aim of our study is to estimate the association of early-life exposure to ambient PM(2.5) with child health outcomes (height-for-age) in India. METHODS: We linked nationally-representative anthropometric data from India’s 2015–2016 Demographic and Health Survey (n = 218,152 children under five across 640 districts of India) with satellite-based PM(2.5) exposure (concentration) data. We then applied fixed effects regression to assess the association between early-life ambient PM(2.5) and subsequent height-for-age, analyzing whether deviations in air pollution from the seasonal average for a particular place are associated with deviations in child height from the average for that season in that place, controlling for trends over time, temperature, and birth, mother, and household characteristics. We also explored the timing of exposure and potential non-linearities in the concentration-response relationship. RESULTS: Children in the sample were exposed to an average of 55 μ g/m(3) of PM(2.5) in their birth month. After controlling for potential confounders, a 100 μg/m(3) increase in PM(2.5) in the month of birth was associated with a 0.05 [0.01–0.09] standard deviation reduction in child height. For an average 5 year old girl, this represents a height deficit of 0.24 [0.05–0.43] cm. We also found that exposure to PM(2.5) in the last trimester in utero and in the first few months of life are significantly (p < 0.05) associated with child height deficits. We did not observe a decreasing marginal risk at high levels of exposure. CONCLUSIONS: India experiences some of the worst air pollution in the world. To our knowledge, this is the first study to estimate the association of early-life exposure to ambient PM(2.5) on child height-for-age at the range of ambient pollution exposures observed in India. Because average exposure to ambient PM(2.5) is high in India, where child height-for-age is a critical challenge in human development, our results highlight ambient air pollution as a public health policy priority. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12940-019-0501-7) contains supplementary material, which is available to authorized users.