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By Catherine Clabby

Where we live determines many of the health risks we contend with. But no one possesses a map of all hazards near home.

With studies in Durham, a North Carolina Central University professor is filling some gaps relevant to older, poorer neighborhoods like those found in many small North Carolina cities and beyond.

John Bang helped lead a project that measured particle-pollution and ozone levels adjacent to a cluster of roads near his university’s campus. To deepen the view, the project documented weather, traffic and other conditions likely to affect the level of exposure.

One finding is that particulate pollution was highest in the winter months during morning commute times. That’s likely because layers of warmer air can trap colder air, holding airborne particles close to the ground during that time of year and preventing contaminants from dispersing.

Such findings produce needed insight into the implications of land use, the physician-scientist said.

“The question is what can you do about it?” he asked. “If we can’t change the layout of a neighborhood, what is the remediation we can do?”

Measuring risks

Bang has long been interested in how people with limited financial means frequently are exposed to more pollution than the wealthy.

At the University of Texas at El Paso, he studied really tiny, nano-scale particulate pollution in that US-Mexico border region. He observed that low-income people in the nearby Mexican city of Juárez would burn whatever they could find as cooking fuel, even old car tires, increasing their exposure to air contaminants.

Research shows that people who live or spend a lot of time near roads with dense traffic have increased incidence of asthma attacks and may be at greater risk of impaired lung function and cardiovascular disease.

Soot sizes and what particles can do:

  • Coarse particles (PM 10) – particulates ≤ 10 micrometers. For comparison, a human hair is about 70 micrometers wide. This is about the same size as some fine pollen.
  • Fine particles (PM 2.5) – particles with a diameter ≤ 2.5 micrometers. You could fit several thousand PM 2.5 particles on the period at the end of this sentence.
  • Ultrafine particles of diameters below 0.1 micrometer. These are small enough to fit in between the cells lining the lungs.
    Diagram credit: US EPA

Exhaust from petroleum-powered vehicles is one source of particulate pollution, a mix of solid particles and liquid droplets with known health risks. Some particles are small enough for people to inhale deep into their lungs. These “ultrafine” particles can gain  entry to our bloodstreams.

After joining NCCU as a researcher in 2005, Bang suspected that people living in older, sometimes closely packed homes lining busy roads near his campus might be encountering such particulate pollution from car and truck traffic that streamed by.

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Few studies have been conducted to assess pollution risks generated by busy roads in cities. “What we know is based on a lot of studies near highways,” Bang said.

He took detectors to the roads and the front doors of nearby homes. In an unpublished pilot study, he not only confirmed that the pollution existed but that planted shrubs – low-cost, natural barriers – reduced the level of pollution that floated from roads to homes.

Deeper dive

In the project measuring particulate pollution and ozone levels in Durham, Bang’s work was part of a larger study led by N.C. State University environmental researcher Christopher Frey, who has a track record for precisely measuring and making computer models of vehicle emissions.

This image shows variation in the particulate level the NC Central University team measured near campus, with the greatest density (in red) detected at points along Allston Avenue, the road near campus with the heaviest vehicle traffic.

Bang’s NCCU student research team and their collaborators made 1,447 measurements over two years of ultrafine particulate matter on high-traffic and quieter roads cutting through and bordering their campus.

Those findings were analyzed with measurements of ozone, wind directions, speeds and patterns, temperate humidity, and traffic density by Frey’s research team and others at N.C. State. All that data helped build a computer model intended to reliably predict when conditions might be most dangerous in such settings.

“The model shows that personal exposure to ultrafine particle concentrations increases if a person is closer to an intersection or a bus stop, if there is more traffic and more vehicle emissions, and if there is lower wind speed, lower temperature and lower humidity,” Frey said.

Such insights could be of use to people considering where to live and to city planners as they assess the environmental impacts of different land uses in a neighborhood.

“In some places, urban planning is outdated,” Bang said.

Seeing the local

Studies such as this are vital steps to better understanding air quality on the ground in a given community, said Calvin A. Cupini, citizen science program manager with Clean Air Carolina.

“Monitoring is usually done at a county or regional level. That means we have large data gaps when it comes to people’s exposure,” he said.

For instance, EPA’s AirNow network has only 23 air quality measurement stations in a state with 100 counties. Groups such as Clean Air Carolina are taking advantage of advances in technology that recently has allowed them to deploy portable air monitors to get a closer look.

Cupini said his organization wants to partner with Bang and others on a study that would funnel air quality data to people with asthma via a smartphone app.

It would assess whether participants will use such data to avoid conditions that might make them sick.

If it works, that may plug one more data gap.

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Catherine Clabby

Catherine Clabby (senior environmental reporter) is a writer and editor. A former senior editor at American Scientist magazine, Clabby won multiple awards reporting on science, medicine and higher education...

One reply on “Mapping Local Air Pollution”

  1. I also began as a direct provider of care services, (Lic Mental Health Counselor) for 15 years and developed a passion to be more effective on a macro-scale, working to inform and improve state systems to create and enhance treatment systems re: mental health & substance addiction treatment systems and services in MA.

    Thank you for what you do and what you report on. As my family is planning on our return to live in N.C. by 2020, your posts are informing me of areas of great importance to me and I expect will guide me to how I can most productively engage once we are back home.
    Sincerely, Mira Naanes, LMHC, LADC1

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