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Can Highways Contribute to Asthma?

EPA scientists and partners team up to examine the link between road-related air pollution and susceptibility to asthma.

Overhead shot of a highway system

Can living near a highway make you more susceptible to asthma attacks? EPA scientists, together with partners from the University of Michigan, are examining this question through the Near Roadways Exposure to Urban Air Pollutants Study (“NEXUS” for short).

“Over the last 15 years, there's been a lot of public concern about the impact of roadways on community health,” said Dan Costa, National Program Director for EPA’s Clean Air Research Program. “So we’re trying to learn how exposure to traffic can worsen asthma in kids.”

Over the next year, study scientists will be conducting a comprehensive asthma trigger study, using data from more than 60 children living in Detroit who suffer from asthma. Study scientists will look at the mixture of pollutants that originate from Detroit-area highway traffic and how the pollution affects children with asthma. Data collected from air near major highways, as well as in homes and schools will shed more light on the mixture of air pollutants that affect asthma and overall health.

While there is a demonstrable link between roadway pollution and decreased respiratory function, scientists have yet to pinpoint what substances are primarily responsible. Air pollution near roadways can come from several sources: burning fuel, road dust, and tire and break wear, all of which have very different physical and chemical properties.

“We don’t have a really good understanding of which pollutants associated with roadways are especially bad for your health,” explained Alan Vette, an EPA scientist who is working on the current asthma study.

Vette is working with the University of Michigan’s Dr. Stuart Batterman and scientists from across several scientific fields to track air pollution over its entire lifecycle, from identifying its various sources to its ultimate effects on human health.

One of the first steps the scientists are taking is an examination of the composition of air pollution by source. Pollution produced by coal-burning power plants, for instance, has a different specific mix of chemical gases and particles than pollution associated with highways.

Building on lessons learned from past EPA-led research on near roadway air pollution, NEXUS will include studies of air pollutant sources, near-roadway air pollution levels and behaviors, and indoor air quality. During the study, scientists will also compare the toxicity of various air pollutants and conduct an epidemiological analysis of the health effects of air pollution. 

Air monitoring equipment

Air monitoring equipment

“We’re exploring whether pollutants from roadways make viral infections more common and more severe in sensitive populations,” said Dr. Stuart Batterman, who is leading the University of Michigan’s part of the study. Batterman explained that certain types of air pollution may make asthma sufferers more prone to respiratory viruses, which in turn can aggravate asthma symptoms.  

Researchers said Detroit, long the heart of the American automotive industry, presents an ideal study site for several reasons. First, the city has a complex air environment that allows scientists to examine a wide variety of pollution sources, levels, and types. In addition to Detroit’s many heavily-travelled highways, researchers will be able to look at pollution from other sources, including coal-fired power plants, metal refineries, and other heavy industries. They’ll also be able to examine the mix of airborne substances (including mold, pet dander, and tobacco smoke) in study participants’ homes and at several schools in order to compare those levels with the measurements taken at outdoor ambient air quality sampling sites.

Air pollutants sometimes behave differently when in the presence of other air pollutants, and scientists working on the NEXUS program will be examining how these interactions take place and their ultimate impact on health.

EPA scientists tout another good reason to conduct a study the Detroit area:  Community Action Against Asthma (CAAA) ― a participatory research partnership organized by the University of Michigan. The group includes leaders and members of many of Detroit’s communities and citizen groups and has acted as a partner in the NEXUS project from its inception. Davyda Hammond, an EPA scientist who has worked extensively with CAAA, said the group has helped community members engage with researchers in crafting the project’s design and methods.

“They’ve helped with recruitment, and with home visits,” Hammond said. “A lot of times, the residents will feel more comfortable talking with someone from their community.”

Hammond said the NEXUS project has created job opportunities for Detroit residents, employing community members in data-gathering efforts and participant interviews. She said the training they have received to prepare for this work will prepare them for future work in scientific research.

Furthermore, the families participating in the study are being given access to the data collected from their homes. As researchers gather biological data from the children enrolled in the study, they’re also working with CAAA to help the families gain access to health care when needed, and providing information to help reduce asthma triggers in their homes.

“Because of the strong community involvement, we can help them receive the treatment that they need,” Hammond said.

Next Steps

When NEXUS’ data-collection phase ends next year, scientists plan to look for epidemiological patterns: What pollutants are most strongly associated with asthma?

The data will also help scientists test and improve air quality models. By linking data from the ambient sites with data collected from Detroit homes and schools, scientists will be able to better determine how the ambient air is contributing to residents’ overall exposure to pollutants, and how to better predict health effects caused by air pollution. Knowing which chemicals are the most harmful will allow policymakers to make better-informed decisions about clean air policies in their communities – targeting specific chemicals, for example, makes it easier for industry to comply with new clean air regulations.

“Air pollutants all have their own set of causes and effects,” Costa said. “We have the capabilities within EPA to do the trans-disciplinary research necessary to develop a tool that can help decision makers understand how these are going to affect their communities.”

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