Respiratory Emergency Department Visit Associations with Exposures to Fine Particulate Matter Mass, Constituents, and Sources in Dhaka, Bangladesh Air Pollution.

Rationale: To date, there is no published local epidemiological evidence documenting the respiratory health effects of source-specific air pollution in South Asia, where particulate matter ⩽2.5 µm in aerodynamic diameter (PM2.5) composition is different from past studies. Differences include more biomass and residue crop-burning emissions, which may have differing health implications. Objectives: We assessed PM2.5 associations with respiratory emergency department (ED) visits in a biomass-burning-dominated high-pollution region and evaluated their variability by pollution source and composition. Methods: Time-series regression modeling was applied to daily ED visits from January 2014 through December 2017. Air pollutant effect sizes were estimated after addressing long-term trends and seasonality, day of week, holidays, relative humidity, ambient temperature, and the effect modification by season, age, and sex. Results: PM2.5 yielded a significant association with increased respiratory ED visits (0.84%; 95% confidence interval, 0.33-1.35%) per 10-µg/m3 increase. The PM2.5 health effect size varied with season, the highest being during monsoon season, when fossil-fuel combustion sources dominated exposures. Results from a source-specific health effect analysis were also consistent with fossil-fuel PM2.5 having a larger effect size per 10 µg/m3 than PM2.5 from other sources (fossil-fuel PM2.5: 2.79% [0.33-5.31%], biomass-burning PM2.5: 1.27% [0-2.54%], and other PM2.5: 0.95% [0.06-1.85%]). Age-specific associations varied, with children and older adults being disproportionately affected by the air pollution, especially by the combustion-related particles. Conclusions: This study provided novel and important evidence that respiratory health in Dhaka is significantly affected by particle air pollution, with a greater health impact by fossil-fuel combustion-derived PM2.5.