03:11pm Tuesday 19 September 2017

Every Breath You Take

Common sense says that living near a highway means the air you breathe isn’t all that good. What is less well known is exactly how polluted that air really is, and how the health of people who live nearby is affected.

A team of Tufts researchers is closer to answering some of those questions now that they are more than halfway through a five-year project that will provide a wealth of information for three communities that border I-93, the highway that runs through Boston.

A key component of the study—monitoring the air quality—is nearing completion, and researchers now know, for example, that the highest levels of pollutants occur on weekday mornings in winter, says John Durant, an associate professor of civil and environmental engineering.

“A staggering percentage of Americans live within a very short distance of highways; on the order of 30 million people live within 200 meters of one,” Durant says. “We’re trying to figure out if there are specific health impacts of living close to the highway that are associated with a particular suite of traffic-related air pollutants .”

The $2.5 million Community Assessment of Freeway Exposure and Health (CAFEH) study, funded by the National Institute of Environmental Health Sciences, involves monitoring air quality and studying the health of more than 150 people each in Somerville, Dorchester/South Boston and Chinatown, as well as an additional 150 people in control groups.

Study participants answer a lengthy questionnaire about health status, diet, exercise and cardiovascular disease. Participants also have their blood analyzed for markers of exposure to contaminants. “Relatively little work has been done to study the effects of exposure to pollutants near highways on cardiovascular health,” which this project includes, Durant says. “Most of the previous research has focused on respiratory problems such as reduced lung function and asthma.”

The principal investigator on the study is Doug Brugge, a professor of public health and community medicine and director of the Tufts Community Research Center at the Tisch College of Citizenship and Public Service. Brugge leads an array of researchers, including field workers and scientists from Tufts, Harvard, local hospitals and community groups. Four community groups are involved in CAFEH, which is an example of a community-based participatory research project. Brugge said not all the data has been collected or analyzed and that he hopes to be able to report on connections between air pollution and health problems within the next year.

40,000 Pieces of Data for Every Trip

Durant is in charge of monitoring air quality in the three neighborhoods, where he and his students are measuring seven specific contaminants. While previous near-highway research has relied on data from a small number of stationary sites, Durant’s work is different: he uses a van equipped with fast-response air pollution monitoring equipment.

Every week over the past year, the van has patrolled the same neighborhoods, driving the same circuit of roads for five or six hours at a time. The drivers are graduate and undergraduate students from the School of Engineering, as well as members of the communities being studied. The van travels its route one or two days a week.

“Each time we go out, we get about 40,000 data points,” says Durant. “That’s the beauty of mobile monitoring; you get a tremendous amount of data that allows you to characterize variation in both time and space.” It’s important to collect information throughout the year, Durant says, as well as on weekends and weekdays and at different times of the day to get a complete understanding of what’s going on.

It turns out that many things affect air pollution levels: proximity to the highway, wind speed and direction, traffic volume, the day of the week and the season. The highest concentration of pollutants tend to be found closest to the highway during winter weekday mornings.

Why winter? On cold mornings, Durant explains, a car’s catalytic converter has not had a chance to warm up, so it doesn’t work as efficiently to convert the pollutants in the exhaust. Also, on early winter mornings the atmospheric conditions are relatively stable, meaning pollutants are less likely to be diluted by wind. Thus, the combination of higher than average emissions rates and low mixing results in high concentrations of pollutants.

Among the pollutants being monitored are polycyclic aromatic hydrocarbons, nitrogen oxides, black carbon—a component of airborne particles that is also a factor in global warming—as well as ultrafine particles, fine dust particles less than 100 nanometers in diameter.

“A lot of the pollutants we’re studying have been looked at for a long time by the health community, and some are regulated by the Environmental Protection Agency,” says Durant. But ultrafine particles are not regulated because there is not enough data to convince regulators of the severity of the problem or to enable them to set air quality standards for these particles.

“These are the smallest particles out there, ranging from a few nanometers to a few microns in size,” he says. “Every time you take a breath of air near a highway, you’re exposed to tens of millions of particles per lung volume. They are so small that they can cross into the bloodstream.”

While air quality monitoring has been completed in two neighborhoods, work is still going on in Boston’s Chinatown neighborhood. One of the benefits of the study, says Durant, is that much of the research involves both graduate and undergraduate students from the School of Engineering. Some are even using the material for thesis work. Other researchers at the medical school are at work studying the blood samples.

Next, Durant and one of his graduate students, Allison Patton, E13, will develop a model that will be able to predict study participants’ potential exposure to a particular pollutant over time, taking into consideration where they live and traffic volume, as well as wind speed and direction. Doug Brugge’s team will then be able to look for epidemiological associations between exposure predictions and health effects.

“Once you have enough data to show that an environmental insult is associated with a particular health effect, people in the public-policy arena can make better decisions,” such as regulating those fine particles or minimizing exposures, says Durant. For example, people who live near highways could be provided with subsidized air filtration systems for their homes, and policymakers could require better exhaust systems for cars, provide incentives for people to use public transportation or modify people’s driving schedules.

Marjorie Howard can be reached at marjorie.howard@tufts.edu.


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