Traffic Pollution Linked to Birth Defects

BY ON May 6, 2013

Pregnant woman standing in front of a red car

Children and cars do not mix well. What comes out of tailpipes has been linked to stroke, heart attacks, and increased hospital admissions in adults, but children seem to be particularly vulnerable traffic pollution, possibly because their organs are still developing and are therefore more vulnerable to the health impacts of pollution.

For one thing, traffic pollution triggers asthma attacks among children who already have the disease. For another, scientists are amassing evidence that traffic pollution actually causes chronic asthma to develop –14% of chronic childhood asthma in Europe was attributed to traffic pollution in a recent study.

A new study suggests that traffic pollution may also harm babies before they are born.

Moms in California’s polluted San Joaquin Valley who breathed traffic pollution early in their pregnancies were more likely to have babies with birth defects compared to moms who breathed less traffic pollution, according to a recent study in the American Journal of Epidemiology. Amy Padula, a postdoctoral fellow at Stanford University’s School of Medicine and the lead author of the study, used air quality data collected by the EPA to estimate the traffic pollution exposure of more than 800 moms who had babies with birth defects, and compared those moms with more than 800 others who had babies without birth defects.

What led Padula to look at birth defects? In prior research, Padula had looked at the links between air pollution and low birth weight. Those links are strong and compelling – many large studies have shown that air pollution, in particular fine particles, or soot, can reduce birth weight. Padula wondered if there might be a link with other “adverse birth outcomes,” to use the researcher term for harm to babies.

The researchers looked at where the mom lived at the beginning of her pregnancy, which is when neural tube defects such as spina bifida and cleft palate occur. They then linked detailed air pollution data, including traffic density, to these locations.

The study found an increased risk of neural tube defects associated with specific air pollutants. As Padula wrote in an email, “carbon monoxide was associated with spina bifida, nitrogen oxide with anencephaly, and both with nitrogen dioxide.”

Padula was quick to note that the results to do not prove that traffic pollution causes neural tube defects, and that more studies are needed. But she admitted the importance of the finding, because, as she wrote, “If this association is confirmed by other studies, it will represent a potential target for intervention to reduce birth defects.”

In other words, we could actually reduce some neural tube defects – which affect some 3000 babies born each year, according to the March of Dimes – by reducing traffic pollution.

The pollutants implicated in Padula’s study, carbon monoxide and oxides of nitrogen (NOx), are both slated to be slashed under EPA’s proposed standards for cleaner gasoline and car engines, also called Tier 3. When the proposed standard is fully implemented, car emissions of carbon monoxide would be reduced by 30%, and those of NOx would be reduced by 25%.

Carbon monoxide exposure during pregnancy was also recently linked to the development of childhood cancers, including leukemia, in research presented at a scientific meeting.

With the Tier 3 standards, we have the chance to reduce pollution known to increase the risk of heart disease and asthma attacks, and suspected of increasing the risk of neural tube birth defects and childhood cancer, all at a cost of less than a penny per gallon of gasoline. The Tier 3 standards are supported by a broad coalition of stakeholders, including auto manufacturers and health professionals, and are opposed by just one group: Big Oil. Tell the EPA to put our children’s health first, and finalize the Tier 3 standards.


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TOPICS: Clean Air Rules and Regulations, Pollution