A population-based cohort study of traffic congestion and infant growth using connected vehicle data
This study investigates the impact of traffic congestion on fetal growth, finding that increased congestion is associated with a reduction in term birth weight by 8.9 grams among a cohort of over 579,000 births in Texas. The research suggests that addressing traffic congestion could have significant benefits for infant health, potentially affecting up to 1.2 million pregnancies annually in the U.S.
College of Health researcher(s)
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.
Traffic Congestion and Birth Weight: Frequently Asked Questions
What is the main finding of the study?
This population-based cohort study found a consistent association between traffic congestion and reduced term birth weight, even after adjusting for factors like sociodemographic characteristics, traffic volume, and other environmental exposures. This suggests that traffic congestion may have a unique and harmful impact on fetal growth.
How was traffic congestion measured in the study?
The study leveraged connected vehicle data from the Texas' Most Congested Roadways database. This database utilizes information from vehicles and devices to calculate congestion metrics, such as annual delay per mile, for specific road segments. Researchers linked these metrics to maternal addresses at the time of delivery to estimate traffic congestion exposure.
What is the difference between traffic volume and traffic congestion?
While related, traffic volume and traffic congestion are distinct concepts. Traffic volume refers to the number of vehicles traveling on a given road, while traffic congestion is characterized by roads operating at lower than free-flow speeds due to an excess of vehicles. Congestion can significantly increase emissions and local air pollutant concentrations.
How does traffic congestion contribute to air pollution?
Traffic congestion exacerbates air pollution by increasing vehicle emissions. When vehicles are stuck in traffic, they idle and accelerate more frequently, leading to higher levels of pollutants like carbon dioxide, particulate matter, and nitrogen dioxide.
What are the potential health implications of traffic congestion?
The study highlights that traffic congestion, beyond just traffic volume, may be linked to adverse reproductive and infant health outcomes. Specifically, the study found an association between traffic congestion and reduced term birth weight. Other potential health impacts from congestion-related pollution could include respiratory problems and cardiovascular issues.
How many pregnancies in the United States might be affected by traffic congestion?
The study estimates that up to 1.2 million pregnancies annually in the United States may be exposed to levels of traffic congestion associated with reduced infant growth, with approximately 256,000 pregnancies in the highest congestion zones. This suggests a potentially significant public health concern related to traffic congestion.
What are the policy implications of the study's findings?
The study emphasizes that policies and infrastructure changes aimed at reducing traffic congestion could yield substantial benefits for infant health. Such interventions could include electronic tolling, congestion pricing, and improvements to public transportation. The authors argue that health impacts should be considered when evaluating the benefits of congestion-reducing policies.
What are the limitations of the study?
The study acknowledges several limitations:
- Traffic congestion data was at an annual scale, limiting the ability to examine trimester-specific effects.
- Vehicle fleet mixture variations couldn't be fully accounted for, potentially leading to exposure misclassification.
- Residential mobility during pregnancy wasn't captured in the birth certificate data, potentially introducing bias.
- The study lacked data on certain potential confounding factors, such as nutrition and lifestyle factors.
- Despite these limitations, the study's findings remain consistent across several sensitivity analyses, suggesting robustness in their main conclusions.