This is the first story in a three-part series on transportation-related air pollution in the Boston area. Read Part 2 here and Part 3 here.

Highways are crucial arteries of our transportation system, but the air pollution from all those vehicles could pose a serious health risk to anyone living, working or going to school near a highway.

New research from a number of Boston-area universities shows transportation-related air pollution may be even more harmful than previously understood, leaving some of society’s most vulnerable at greater risk for heart attack and stroke.

Ken Kimmell of the Union of Concerned Scientists raised the issue at a June press conference at the Josiah Quincy Upper School in Chinatown, when discussing a new air quality report.

"Right here where we're standing, our modeling indicates it is the most polluted, the most exposed transportation pollution site in all of the commonwealth," Kimmell said, standing on the school's basketball court. That's because just beyond the courts is the Mass Pike. And, just around the corner, the Pike intersects with I-93.

Students at the Josaiah Quincy School in Boston play on the school’s basketball courts after dismissal. The school, and its outdoor playing spaces, run alongside two major highways: the Massachusetts Turnpike and I-93. Meredith Nierman / WGBH News

Doug Brugge used to work in Chinatown as a public health professor at Tufts Medical Center. Before he left to go teach at the University of Connecticut, he wrote a book: “Particles in the Air: the Deadliest Pollutant is One You Breathe Every Day.”

"Most of the public, if they were asked to rank environmental concerns, would not understand that particulate matter air pollution should be — if you measure this by the number of people who die and are made sick, and by the economic impact — then particulate matter air pollution should be at the top of the list, and by a long shot," Brugge said.

Particulate matter comes in a variety of sizes — all of them small. Until recently, most research has focused on the health impacts of particles that are 2.5 microns in diameter — 20 times smaller than the width of a human hair. That kind of pollution is regulated by the EPA. But scientists are just now realizing it’s the smallest particulates — 0.1 microns or smaller — that we’re most exposed to, and may be having the most significant health impact.

"The ultrafine particles start out as gases and when they come out of the tailpipe they're heated, very hot gases, and then they begin condensing in the air," Brugge said. "And so that's why they're so tiny."

A team of Tufts researchers has been studying the impact of these incredibly small particles in Chinatown, Somerville and other communities for more than a decade. And they've shown that ultrafines are so tiny, they don't just affect the lungs. They're small enough to go directly into the bloodstream and cause inflammation, leading to the most common cause of death in the United States — cardiovascular disease.

"That is basically strokes and heart attacks," Brugge said.

Other research has linked ultrafine particles to autism, Alzheimers and neurological problems. Scientists at several universities in the area are eager to know where the highest concentrations of these tiny particles are, and how to reduce human exposure.

For John Durant of Tufts University, that means driving around in an electric Chevy Bolt, measuring air quality in Boston-area neighborhoods near the highways.

"It's pretty tight in here and a little bit noisy," Durant said as he navigated Somerville's roads in the mobile laboratory recently. The entire back of the car is full of computer equipment, and a fan pulls air in from the outside. A laptop in the passenger seat shows a moving bar graph, illustrating levels of traffic-related air pollution outside.

"And on the screen there you're seeing in real time the levels of carbon dioxide and ultrafine particles," Durant said.

John Durant of Tufts University measures air pollution in Somerville from a "mobile laboratory." Craig LeMoult / WGBH News

As the car headed closer to I-93, the laptop showed the bar graph jump. This and other research has shown ultrafines are at their highest concentrations near highways, and drop off considerably between 150 and 200 meters from roadways.

"OK, here's a little peak right there that just came up," Durant said as he monitored the results. He and his team have driven this mobile laboratory on the same route through the streets of Somerville hundreds of times for this study.

"Somerville is, for better or for worse, it's a perfect city to perform this kind of study because the highway was put in here right on top of existing neighborhoods back in the '60s," he said. "And I guess relatively little consideration was given to air pollution impacts on the surrounding communities."

This map shows the Massachusetts major highways (interstate, U.S. Highways and state highways) along with all schools and long-term care facilities. The orange area identifies exposure areas of concern within 200 meters. Source: MassGIS (Bureau of Geographic Information), Commonwealth of Massachusetts EOTSS. Credit: Kevin J. Lane PhD/Boston University School of Public Health

Jon Levy of Boston University says that's what happened in low income communities around the state. He leads a research team that's also studying where this pollution is and the inequity behind who's being exposed.

"The lower your income, in general, the higher your level of pollution exposure," Levy said.

Levy's research also found minorities in Massachusetts are breathing in more of this stuff than white people because of living in communities with greater exposure. And those with lower educational attainment have more exposure than more educated people. Massachusetts is currently working with eight other states to develop a policy for reducing the region's transportation emissions.

But even if the state can figure out how to do that, it's going to take some time. And some, like Somerville resident Ellin Reisner, said we need to limit exposure now.

"So we're standing literally, probably 30 feet from the highway right now," Reisner said as she stood in a residential neighborhood of Somerville bordering I-93. Reisner, who is the president of the Somerville Transportation Equity Partnership, said they'd like to see more 30-foot walls separating her community from 93. Those walls are designed to block the highway's noise, but Reisner points to EPA research showing they have a beneficial side effect.

"We know that the sound barriers would reduce the exposure because it pushes the ultrafine particulates up and over where people live," she said.

And once the pollution gets pushed up and over the neighboring communities, it becomes dispersed, reducing the health impact. For now, though, the state Department of Transportation, which is responsible for the barriers, said there's no plan to build any walls for the purpose of blocking air pollution.

Correction: A previous version of this story identified researcher John Levy as being at Harvard. Levy is a researcher at Boston University.

