Perinatal exposure to particulate matter, environmental tobacco smoke and respiratory symptoms in Mexican children

Abstract

Background: Particulate matter <2.5 microns in diameter (PM2.5) and environmental tobacco smoke (ETS) are associated with respiratory morbidity starting in utero. However, their potential synergistic effects have not been completely elucidated. Here, we examined the joint effects of perinatal PM2.5 and prenatal ETS exposure on respiratory outcomes in children. Methods: We studied 514 mother-child dyads in the Programming Research in Obesity, Growth, Environment and Social Stressors study in Mexico City. Exposure to PM2.5 was estimated using residence in pregnancy and child’s first year of life and a satellite-based spatio-temporal model. ETS exposure was assessed by caregiver’s report of any smoker in household during second or third trimester. Outcomes included report of ever wheeze, wheeze in the past 12 months (current wheeze) and ever diagnosis of asthma assessed at 6-7 year visit in separate models. Associations were modeled using distributed lag models with daily PM2.5 averages for pregnancy and the first year of life, adjusting for child’s sex, birth weight z-score, mother’s age and education at enrollment, maternal asthma, season and stratified by prenatal ETS exposure (yes/no). Results: Exposure to ETS was reported in 178/514 participants (34.6%). We found significant associations between higher perinatal PM2.5 exposure and higher cumulative odds of ever wheeze(OR:3.72, 95%CI [1.37, 10.10] per 5 µg/m3) and wheezing in the past year at age 6 (OR:6.98, 95%CI [1.30, 37.50] per 5 µg/m3) only in children with ETS exposure. We did not find any evidence of an association between perinatal PM2.5 exposure and report of ever diagnosis of asthma or effect modification of the association by ETS exposure. Conclusions: Exposure to prenatal ETS modified the association between perinatal PM2.5 exposure and respiratory outcomes at age 6-7 years. It is important to consider concurrent chemical exposures to more comprehensively characterize children's environmental risk.