A population-based cohort study of traffic congestion and infant growth using connected vehicle data

Abstract

More than 11 million Americans reside within 150 meters of a highway, an area of high air pollution exposure. Traffic congestion further contributes to environmental pollution (e.g., air and noise), but its unique importance for population health is unclear. We hypothesized that degraded environmental quality specifically from traffic congestion has harmful impacts on fetal growth. Using a population-based cohort of births in Texas (2015-2016), we leveraged connected vehicle data to calculate traffic congestion metrics around each maternal address at delivery. Among 579,122 births, we found consistent adverse associations between traffic congestion and reduced term birth weight (8.9 grams), even after accounting for sociodemographic characteristics, typical traffic volume, and diverse environmental coexposures. We estimated that up to 1.2 million pregnancies annually may be exposed to traffic congestion (27% of births in the United States), with ~256,000 in the highest congestion zones. Therefore, improvements to traffic congestion may yield positive cobenefits for infant health.

Fig. 1.. Conceptual diagram of the different components contributing to increased traffic-related environmental pollution exposures.

Most studies to date quantify only road proximity and traffic volume.

Fig. 2.. A comparison of traffic characteristics in Houston, Texas, 2016.

Displayed data show road segments by traffic volume and percent of total greenhouse gas (GHG) emissions due to congestion.

Fig. 3.. Restricted cubic splines of the association between metrics of traffic delay and term birth weight.

The solid line is the prediction for mean term birth weight, and the shaded area is the 95% CI band. Models contain a covariate for total VMT within the respective buffer of the residence. On the basis of the data distribution, splines were fit with six knot points at the following percentiles: 0, 5, 25, 50, 75, and 95.

Fig. 4.. Adjusted associations between the highest quartile of total delay within 500 m of mother’s addresses and term birth weight for different sensitivity analyses.

Model 1 contained a covariate for VMT within the respective buffer of the residence. Model 2 contained the following covariates: County of maternal residence at delivery (indicator for each county), birth year, birth month, maternal age, infant sex, maternal race, maternal ethnicity, maternal educational attainment, method of payment for delivery, maternal cigarette usage, month of prenatal care initiation, prepregnancy body mass index, infant gestational age, and total VMT within the respective buffer of the residence. Model 3 contained the covariates from model 2 with the addition of the following: Area deprivation index (state ranking for Texas), transportation noise, previous year concentration of PM_2.5, previous year concentration of NO₂, previous year concentration of ultrafine particles, and green space within 500 m of the residence (measured by NDVI). All restricted models use the covariates from the fully adjusted model (i.e., model 3), except for the covariate related to the restriction that is removed if included in fully adjusted model specifications.