Low birth weight at term and the presence of fine particulate matter and carbon monoxide in the Brazilian Amazon: a population-based retrospective cohort study

Background: Although studies have shown an association between air pollutants from anthropogenic sources and pregnancy outcomes, little is known regarding the association between low birth weight (LBW) and exposure to emissions of biomass burning. Methods: This population-based retrospective cohort study assessed the effect of exposure to particulate matter and carbon monoxide (CO) from biomass burning in the Amazon and cerrado (Brazilian savanna) biomes on term LBW (< 2500 g) in cities of Mato Grosso, Brazil. Data on births were obtained from the Information System on Live Births of the Ministry of Health. The exclusion criteria were a twin pregnancy, gestational age of less than 37 weeks, and congenital malformation diagnosed at birth. For exposure variables, we used a historical series of daily average concentrations of particulate matter with a diameter less than 2.5 m (PM2.5) and CO provided by Coupled Aerosol and Trace Gases Transport Model for the Brazilian Development of the Regional Atmospheric Modeling System developed at the National Institute for Space National Center for Weather Forecasts and Climate Studies, National Institute for Space Research. Maternal exposure was estimated by the average amount of pollutants for each trimester and for the entire period of gestation. The association between air pollutants and LBW was analyzed by multiple logistic regression, adjusting for the newborn's sex, mother's age and education, and prenatal care. Results: A total of 6147 full-term singleton live births were included in the study and 193 (3.1%) were LBW. In adjusted analysis, the number of prenatal visits and maternal education with 8 years or more were associated with LBW. The association between exposure to air pollutants and the risk of LBW was significant for the 4th quartile of PM2.5 concentrations in the 2nd trimester (OR = 1.51, 95% CI = 1.04 to 2.17) and in the 3rd trimester, and for the 4th quartile of CO concentrations in the 2nd trimester only, in adjusted analysis. Conclusions: This study provides further evidence of the effect of smoke from biomass burning on the occurrence of LBW in cities of the Brazilian Amazon.