Estimating quantitative exposure-response relationships for fine particulate matter and maternal, child and adult respiratory outcomes: Experience from the rural -urban TAPHE cohort in Tamil Nadu, India

Abstract

Background: Air pollution in the household and ambient environment ranks among the leading risk factors contributing to the national burden of disease in India. We describe results from the Tamil Nadu Air Pollution and Health Effects (TAPHE) study that provided some of the first estimates of quantitative exposure-response relationships for air pollution and health in integrated rural-urban cohorts in India.Methods: We followed 1121 pregnant women, 948 (index) children and 1060 adults recruited from 110 villages (rural) and 10 municipal (urban) zones, to establish quantitative exposure -response relationships between fine particulate matter (PM2.5)exposures and birth weight, prevalence of acute respiratory infections (ARI) prevalence of chronic respiratory symptoms and lung function respectively.Results: After adjusting for relevant co-variates, a 10µg/m3 change in PM2.5 exposures was associated with a (i) 4 gm (95% CI: 1.38 gm,7.18gm) decrease in birth weight (ii) 0.3% (95%CI: 0.02%-0.69%) increase in the longitudinal prevalence of ARI among children <2 years of age and (iii) 10% (OR=1.10; 95% CI: 1.048, 1.153) increase in prevalence of respiratory symptoms, a lower FVC [17ml (95% CI:28ml, 5.9ml)] and a lower FEV1[15ml (95% CI:24ml, 4.9ml)] among adults. Mixed models that provided longer-term estimates of exposure consistently increased the effect size estimates for all outcomes.Conclusion: TAPHE methods and results have contributed to numerous follow up efforts across multiple states that are currently expanding the base of quantitative exposure-response response information for ambient and household air pollution. The study also provided important inputs for the household air pollution intervention (HAPIN) trial, one of the first multi-country randomized control trials involving the provision of liquefied petroleum gas (LPG) among pregnant women in biomass using rural households. The trial currently underway in India, Guatemala, Peru and Rwanda is expected to provide major inputs for air quality actions across multiple low and middle income countries.