The association between indoor air pollution and low birth weight in Delhi and Himachal Pradesh, India: a cross-sectional study

Abstract

Low birth weight (LBW) is a serious public health problem associated with increased risk for many diseases including cardiovascular, neurodevelopmental and multiple organ system disorders. India has the highest number of preterm births and newborn deaths globally. There are several risk factors associated with LBW, including indoor air pollution. Indoor air pollution has multiple causes, including use of solid fuels for cooking, which emit particulate matter polluting the indoor air. Tobacco exposure via maternal smoking or passive smoking can cause adverse health effects for the mother and the fetus, including LBW. Smoking inside households, absence of ventilation in households and use of polluting fire stoves significantly contribute to deterioration of indoor air quality. Aim: The aim of this study was to investigate the association between indoor air pollution (IAP) and LBW among infants born during 2014-2016 to mothers living in Delhi and Himachal Pradesh, India. Additionally, the study investigated the association between indoor exposure to tobacco smoke and LBW among the study sample. Methods: The National Family Health Survey-4 dataset was used to conduct secondary data analysis. All the analyses were weighted for sampling to ensure the representativeness of the study sample and reduce sampling error. The variables significantly associated with the outcome in the descriptive analysis were included in univariate regression analysis with the two independent variables to identify the confounders of the associations of interest, and on the basis of the results, the adjusted associations between the outcome of LBW and each of the independent variables – indoor air pollution score and exposure to second-hand smoke, were investigated by performing multivariable logistic regression analysis to control for the identified confounders of each association. Results: Women with LBW babies constituted 22% of the study sample. The study sample included 74% residing in Delhi and 26% in Himachal Pradesh. The mean age of women included in the sample was 26 years. Multivariable logistic regression analysis revealed an insignificant association between the IAP score and odds of having a LBW baby when adjusted for available confounders. A significant association was observed in the adjusted multivariable logistic regression analysis between second-hand smoke (SHS) exposure inside the household and odds of having a LBW baby. Women who were exposed to indoor SHS weekly or more frequently, showed a 42% higher odds of having a LBW baby as compared to those women who were exposed to indoor SHS monthly or less frequently. Conclusion: Interventions targeting reduction of SHS exposure to vulnerable groups like pregnant women could greatly decrease the LBW prevalence attributable to SHS exposure in India. The lack of association between IAP score and LBW could be due to some construct deficiencies of the score used in this study. Therefore, further research using particulate matter monitors to directly quantify the quality of indoor air in India is recommended to determine the true association between IAP and LBW.