Association between ambient air pollution and childhood respiratory diseases in low- and middle-income Asian countries: A systematic review

Abstract Background Ambient air pollution has been associated with respiratory diseases in children. However, little is known about its impact on low- and middle-income countries (LMICs) in Asia. This systematic review investigates and summarises the associations between short- and long-term exposure to ambient air pollutants and childhood respiratory diseases. Methods We conducted a systematic search of peer-reviewed articles on PubMed, Scopus and Ovid MEDLINE. Observation study designs consisting of the cohort, cross-sectional, case-crossover, and time series study were included. The quality assessment was conducted based on the study designs, using the AXIS (Appraisal Tool for Cross-Sectional Studies), NOS (Newcastle-Ottawa scale) and the Mustafic criteria. Each of the included studies was appraised to evaluate the risk of bias using an adapted OHAT (Office of Health Assessment and Translation) assessment tool. Results A total of 41 articles with high and medium quality from 2015 to 2019 were included in this review. The studies reported exposure to a high concentration of ambient air pollution (PM10 n = 25, PM2.5 n = 22, SO2 n = 13, NO2 n = 24, CO n = 5, O3 n = 7) was significantly correlated with increased risk of childhood respiratory morbidity and mortality across different age groups and countries. However, the distribution of the studies did not cover all Asian LMICs. Due to the age group variation, it was impossible to identify specific groups susceptible to ambient air pollution's adverse effects. Conclusion Short- and long-term exposure to ambient air pollution is associated with increased childhood respiratory morbidity and mortality in Asian LMICs. There is a need for more studies focused on the relationship between ambient air pollution and childhood respiratory diseases, especially in Asian countries with poor air quality and rapid urbanisation.