Effects of exposure to biomass combustion in respiratory function

Background: The biomass use for cooking and heating is widespread in many developing countries. This indoor air pollution differs from outdoor in terms of primary pollutants concentration and secondary oxidants. The effects of common air pollution are largely investigated. Although some studies tried to evaluate de impact of the indoor pollution there are still discordant data, especially on respiratory symptoms and functions according to the studied population. We aimed to evaluate respiratory symptoms and function in individuals exposed to biomass and butane gas (GLP) combustion in Brazil.

Methods: We evaluate 1.402 individuals in 220 houses in a rural comunity in the northeast of Brazil. Questionnaires were applied to evaluate respiratory symptoms, social and economic conditions. Black carbon (BC) was analyzed in filters located near the cook stove for three days, using reflectance levels, in three groups (GLP, indoor biomass [IB] and outdoor biomass [OB]. In 50 houses the amount of particulate matter (PM2.5) was quantified. Lung function tests, with and without bronchodilator, were applied in 120 individuals paired for smoking, age and fuel.

Results: BC correlated directly to the amount of PM2.5 (r²=0.901, p<0.001) and was used to evaluate the indoor pollution exposure. There were a significant increase in black carbon index in filters exposed to BC, compared to GLP (p<0.001); there were no differences between IB and OB. The analysis of symptoms between BC and GLP corrected for smoking showed increased odds ratio (OR) for cough (OR=1,42, p=0.002), wheezing (OR=1.6, p=0.001) and dyspnea (OR=1.7, p<0.001). Lung function tests showed that either smokers using GLP and non-smokers using biomass have %predicted FEV1 smaller then non-smokers using GLP (p=0.022 and p=0.002), but no differences between them both where observed (p=0.982).

Conclusion: Exposure to BC may have deleterious effects on respiratory health, either symptoms and function.