Seasonal Modification In The Effect Of Short-Term Exposure To Ambient Fine Particulate Matter On The Lung Function Of School Children In Dhaka, Bangladesh

Abstract

The objective of this study was to investigate the effect of short-term exposure to ambient particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) on lung function and modification of this association by season in school children in Dhaka, the capital of Bangladesh. A panel of total of 314 school children, aged 9-16 years from 3 schools located within 1km of three existing continuous air monitoring stations inside and around Dhaka were recruited. Lung function was assessed repeatedly using spirometry test during winter and summer season in 2013, yielding a total of 6 measurements per child. Daily PM2.5 data were retrieved from nearby air monitoring stations. Linear mixed effects models adjusted for potential confounders were used to examine the effect of the PM2.5 on lung function. To assess the effect modification of season, stratified analyses was performed by dichotomizing winter and summer season and then, the p-value was calculated by a multiple comparison test. The mean PM2.5 level was 88µg/m3 during the total study period. PM2.5 concentration varied greatly between seasons, with higher values observed in winter than in summer. In both seasons, lung function parameters were negatively associated with a 20 µg/m3 increase of PM2.5 on the previous day. In summer, the negative effect of PM2.5 on lung function parameters was stronger than in winter. Specifically, for peak expiratory flow (PEF), there was a - 4.17 (95% CI, -5.69 to -2.65) decrease in winter and -10.92 (95% CI, -15.73 to -6.12) decrease in summer for a 20 µg/m3 increase in PM2.5 on the previous day. This difference in estimates was statistically significant (p