Prenatal Exposure to Traffic Pollution and Childhood Body Mass Index Trajectory

Abstract

Background: Limited evidence suggests an association between prenatal exposure to traffic pollution and greater adiposity in childhood, but the time window during which growth may be most affected is not known.Methods: We studied 1,649 children in Project Viva, a Boston-area pre-birth cohort. We used spatiotemporal models to estimate prenatal residential air pollution exposures and geographic information systems to estimate neighborhood traffic density and roadway proximity. We used weight and stature measurements at clinical and research visits to estimate a BMI trajectory for each child with mixed-effects natural cubic spline models. In primary analyses, we examined associations of residential PM2.5 and black carbon (BC) exposures during the third trimester and neighborhood traffic density and home roadway proximity at birth address with (1) estimated BMI at 6 month intervals through 10 years of age, (2) magnitude and timing of BMI peak and rebound, and (3) overall BMI trajectory. In secondary analyses, we examined associations of residential PM2.5 and BC exposures during the first and second trimesters with BMI outcomes.Results: Median (interquartile range; IQR) concentration of residential air pollution during the third trimester was 11.4 (1.7) μg/m3 for PM2.5 and 0.7 (0.3) μg/m3 for BC. Participants had a median (IQR) of 13 (7) clinical or research BMI measures from 0 to 10 years of age. None of the traffic pollution exposures were significantly associated with any of the BMI outcomes in covariate-adjusted models, although effect estimates were in the hypothesized direction for neighborhood traffic density and home roadway proximity. For example, greater neighborhood traffic density [median (IQR) 857 (1,452) vehicles/day x km of road within 100 m of residential address at delivery] was associated with a higher BMI throughout childhood, with the strongest associations in early childhood [e.g., per IQR increment natural log-transformed neighborhood traffic density, BMI at 12 months of age was 0.05 (−0.03, 0.13) kg/m2 higher and infancy peak BMI was 0.05 (−0.03, 0.14) kg/m2 higher].Conclusions: We found no evidence for a persistent effect of prenatal exposure to traffic pollution on BMI trajectory from birth through mid-childhood in a population exposed to modest levels of air pollution.

Prenatal Ambient Particulate Matter Exposure and Longitudinal Weight Growth Trajectories in Early Childhood

“…Beyond the sex-specific effects, our findings are broadly consistent with a growing literature linking air pollution exposures with childhood growth [19,21,22,52]. In a Boston-area pregnancy cohort, Fleisch et al (2015) found increased odds of weight-for-length > 95th percentile at 6 months of age in fourth quartile third-trimester PM 2.5 and distance to roadway < 50 m compared to the referent groups, though estimates were not statistically significant.…”

“…Inconsistent with our findings, this same study found each interquartile range increase in one-year average PM 2.5 concentrations prior to each measurement occasion was associated with lower BMI-z score and total and truncal fat mass in mid-childhood (average 8 years of age) [52]. Investigators also examined trimester-specific associations, finding no association between third trimester PM 2.5 and BMI outcomes [21].…”

“…Modelling weight as a longitudinal outcome-growth trajectories-is a more informative measure than weight modelled as a cross-sectional outcome to understand steps on the causal pathway between early-life air pollution exposure and morbidities later in life. Few studies have investigated the link between prenatal ambient air pollution exposure and infant and early-childhood growth trajectories [17][18][19][20][21][22].…”

Air pollution and childhood obesity

“…Longitudinal studies from the U.S. Project Viva cohort consistently reported that traffic density and roadway proximity during pregnancy or at delivery are associated with obesity parameters including body mass index (BMI) and fat mass in children aged 6 months to 10 years. [12][13][14] This study group also suggested a possible impact of prenatal air pollution exposure on reduced birth weight. However, other studies on the association between individual traffic-related air pollutants and childhood obesity have not verified this association.…”

“…Most cohort studies from the USA and Hong Kong reported a null impact of PM2.5 and PM10 exposure during pregnancy on obesity parameters in children and adolescents. [12][13][14]16,17) Only 2 cohort studies from Boston, Massachusetts, reported a weak association between PM during pregnancy and obesity parameters including BMI at 2-9 years of age and waist-to-hip ratio at 4 years of age. 18,19) Prenatal exposure to tobacco smoke, a representative source of household air pollution, is reportedly related to an increased risk of overweight at ages 3 and 7 years in large-scale national cohort studies from the USA and the UK.…”