Acute Effects of Particulate Matter and Black Carbon from Seasonal Fires on Peak Expiratory Flow of Schoolchildren in the Brazilian Amazon

Background: Panel studies have shown adverse effects of air pollution from biomass burning on children's health. This study estimated the effect of current levels of outdoor air pollution in the Amazonian dry season on peak expiratory flow (PEF). Methods: A panel study with 234 schoolchildren from 6 to 15 years old living in the municipality of Tangara da Serra, Brazil was conducted. PEF was measured daily in the dry season in 2008. Mixed-effects models and unified modelling repeated for every child were applied. Time trends, temperature, humidity, and subject characteristics were regarded. Inhalable particulate matter (PM10), fine particulate matter (PM2.5), and black carbon (BC) effects were evaluated based on 24-hour exposure lagged by 1 to 5 days and the averages of 2 or 3 days. Polynomial distributed lag models (PDLM) were also applied. Results: The analyses revealed reductions in PEF for PM10 and PM2.5 increases of 10 mu g/m(3) and 1 mu g/m(3) for BC. For PM10, the reductions varied from 0.15 (confidence interval (CI) 95%: -0.29; -0.01) to 0.25 l/min (CI95%: -0.40; -0.10). For PM2.5, they ranged from 0.46 (CI95%: -0.86 to -0.06) to 0.54 l/min (CI95%: -0.95; -0.14). As for BC, the reduction was approximately 1.40 l/min. In relation to PDLM, adverse effects were noticed in models based on the exposure on the current day through the previous 3 days (PDLM 0-3) and on the current day through the previous 5 days (PDLM 0-5), specially for PM10. For all children, for PDLM 0-5 the global effect was important for PM10, with PEF reduction of 0.31 l/min (CI95%: -0.56; -0.05). Also, reductions in lags 3 and 4 were observed. These associations were stronger for children between 6 and 8 years old. Conclusion: Reductions in PEF were associated with air pollution, mainly for lagged exposures of 3 to 5 days and for younger children.