Indoor exposure to particulate matter and acute lower respiratory infections in young children in urban Bangladesh

Background: Acute lower respiratory infection (ALRI) is the leading cause of death in children under 5 years of age in Bangladesh. Indoor exposure particulate matter (PM) has been consistently associated with increased risk of ALRI in children, but indoor concentrations of PM, their determinants, and association with ALRI in low-income communities remain poorly characterized. This study aimed to describe the seasonality and determinants of PM2.5 concentrations in a low-income, urban community in Mirpur, Dhaka, Bangladesh and to investigate the relationship between PM2.5 mum in diameter (PM2.5) and ALRI in children less than 2 years of age.;Methods: During January 2008 -- March 2011 children were enrolled at birth and followed-up in the home for signs or symptoms of ALRI twice weekly through their second birthday. Physicians diagnosed ALRI as respiratory illnesses with rapid respiration, chest indrawing, or crepitations. During May 2009 -- April 2010, PM2.5 concentrations were measured once per month in the children's sleeping spaces. Linear regression was used to estimate the effects of household characteristics and season on PM 2.5 concentrations. The association between PM2.5 concentrations and risk of ALRI was estimated with Poisson regression and a generalized gamma distribution model was used to calculate the relative age at the first ALRI episode associated with PM2.5 concentrations in the home.;Results: Two hundred and fifty-seven children were enrolled in the study and completed data collection. Time-weighted average PM 2.5 concentrations indoors were 190 mug/m3 (95% CI 170 -- 210). Households cooking with biomass had PM2.5 concentrations 75 mug/m3 (95% CI 56 -- 124) greater than other homes. PM2.5 concentrations were also associated with burning kerosene, indoor smoking, and ventilation, and were more than twice as high during winter than during other seasons. One hundred sixty-nine children (66%) experienced ALRI before 24 months of age; 25% by 3.3 months and 50% by 8 months. We observed 0.7 (95% CI 0.7 -- 0.8) episodes of ALRI per child per year and each hour that PM2.5 concentrations exceeded 100 mug/m3 was associated with a 7% increase in incidence of ALRI among children aged 0 -- 11 months (adjusted IRR 1.07, 95% CI 1.01 -- 1.14), but not in children 12 -- 23 months old (adjusted IRR 1.00, 95% CI 0.92 -- 1.09). Each hour that PM2.5 was >100 mug/m3 was independently associated with a 12% decrease in the age at first ALRI episode.;Conclusion: Time-weighted average PM2.5 concentrations in our study homes were approximately 7 times higher than the daily mean PM 2.5 guidelines recommended by the World Health Organization. Findings from our study suggest that interventions to reduce PM2.5 concentrations in study children's homes could meaningfully reduce the burden of ALRI among infants.