Prenatal Exposure to PM2.5 in a Birth Cohort of Mexico City: The Influence of Season of the Year at Time of Conception

摘要

Background. Due to well established relevance of season on air pollution assessment, we estimated prenatal PM2.5 (particulate matter < 2.5 microns) exposure by season of the year at different gestational ages. Methods. 944 pregnant women were georeferenced by home addresses between 2007 and 2011 in Mexico City. Prenatal exposure to PM2.5 was estimated using methods of (ⅰ) proximity; (ⅱ) proximity with imputed data; and (ⅲ) hybrid satellite model. Non parametric Wilcoxon signed-rank tests were used to compare exposure methods, and root mean square error to measure the magnitude of differences. Results. Average exposure to PM2.5 during all pregnancy ranged from 20.4 to 22.9 μg/m3 No differences were found between methods for assigning exposure (p <0.05). Pregnancies that started in cold-dry season had a higher average concentration throughout the gestation period (25.7 to 26.3 μg / m3) compared to pregnancies that started during the rainy season (18.1 to 19.7 μg / m3). Conclusion. Variations in prenatal exposure levels were attributed to seasonal differences and not to the methods for assessing exposure. These results provided information about how changes to exposure based on season of conception are relevant to adverse birth outcomes.