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Traffic-Related Air Pollution and Children’s Health

Expectant mother and child on a balcony

Traffic-Related Air Pollution and Selected Health Outcomes

Traffic-related air pollutants are defined as those primarily emitted by mobile sources due to combustion of fossil fuels by passenger cars, diesel trucks and buses, and “non-road” equipment (e.g., recreational vehicles, lawn and garden equipment, etc.). Traffic-related air pollution contributes significantly to ambient air pollution, especially in urban settings. Children represent a subpopulation that is sensitive to air pollution, and there is increasing evidence that exposure to traffic-related air pollution may impact pregnancy outcomes and several facets of development, including neurological function. The NTP is currently conducting two systematic reviews to evaluate the evidence for an association between exposure to traffic-related air pollution and 1) hypertensive disorders of pregnancy and 2) neurological disorders and adverse neurobehavioral outcomes during development.

The systematic reviews were proposed as a nomination to the NTP in July 2012 to evaluate emerging children’s health issues associated with exposure to ambient air pollution, including traffic-related air pollution, and the scope was narrowed to focus on traffic-derived air pollutants. The reviews will consist of evidence evaluated from human, experimental animal, and mechanistic studies (where applicable), and traffic-related air pollution will be characterized by direct traffic measurements (e.g., distance to main roads, traffic volume, etc.) and measurements of traffic-related air pollutants (e.g., CO, NOx, PM2.5, etc.).

NTP’s Systematic Review on Traffic-Related Air Pollution

Hypertensive Disorders of Pregnancy

Hypertensive disorders of pregnancy complicate up to 10% of pregnancies worldwide and are a leading cause of maternal and fetal morbidity and mortality. These disorders are defined by hypertension (> 140/90 mmHg), usually during the second half of pregnancy, and range in severity from hypertension alone to multi-organ dysfunction and seizures in the mother. Of direct relevance to children’s health, infants born to mothers with hypertension during pregnancy are at higher risk for preterm delivery, low birthweight, being small for gestational age at birth, and an array of prematurity-related neonatal diseases. Although associations between traffic-related air pollution exposure and adverse cardiovascular outcomes in susceptible sub-populations are less studied, there is a growing body of evidence suggesting that traffic-related air pollution may adversely impact maternal blood pressure, ultimately leading to increased risk for adverse health outcomes in the infant.

Neurological Development

Neurological disorders, such as attention deficit/hyperactivity disorder and autism, and neurobehavioral outcomes (e.g. intelligence quotient, language, and motor skills) can be impacted by environmental chemicals. There is evidence that traffic-related air pollutants can enter the circulation and reach the brain in children, and it is hypothesized that induction of oxidative stress and inflammation and modification of neurotransmitters and other biochemical signals by air pollutants may impact neurobehavioral outcomes during development.

Documents

  • Protocol for ongoing systemic review (June 2016)
    • Proposed NTP Evaluation on Traffic-Related Air Pollution Concept (April 2014)
    • Presentation (April 2014) NTP Board of Scientific Counselors (April 16-18, 2014)
    • Request for Information on Nomination (Federal Register notice for nomination-July 13, 2012 PDF HTML)