Pitt study shows buses main source of diesel pollution

Although public transportation like Pittsburgh’s Port Authority reduce the total number of vehicles on the road, the emissions from its buses are still a leading contributor to air pollution Downtown, a study released Tuesday found.

The study, which came from the Allegheny County Health Department and Pitt’s School of Public Health, said public buses could be contributing more to air pollution in Downtown Pittsburgh than the other vehicles that drive there.

The two-year study monitored diesel pollution levels at 36 sites across Downtown,  including sites near Point State Park, the Gateway Center and Steel Plaza. At each monitoring site, researchers measured spatial variation in pollution levels — or how the pollution level differed in parts of Downtown — and patterns based on time of day. The next two papers in the series of studies will be released within six months to a year.

Jane Clougherty — the lead researcher of the study and an associate professor in Pitt’s Public Health Department — said that although the results pointed to buses as a contributor to the diesel pollution, buses should not be dismissed. These vehicles reduce the number of cars on the road, which could lead to an overall reduction in emissions.

“Each bus can take 50 cars off the road,” Clougherty said. “On a per person basis, buses are still a great thing.”

Adam Brandolph, Port Authority’s public relations representative, agreed, adding that Port Authority is also investing in “an aggressive bus-replacement schedule,” which replaces older vehicles with more environmentally-friendly buses.

“We have also been looking into the purchase of alternative-fuel vehicles and plan to do so as soon as we have the infrastructure built to support them,” Brandolph said in an email.

In an effort to decrease bus contribution to the city’s pollution, Port Authority is working to replace their entire bus fleet by 2020, and they expect to update most buses with new technology that produces less diesel emission by next year, according to Claughtery.

Areas of “transit bus activity” — places where several bus stops are close to each other and several bus lines run through — tend to be areas of high diesel pollution levels. Bus activity was a more reliable predictor of diesel pollution than car, truck and train usage, according to the study. Delivery trucks and parking garage activity followed behind buses as predictors of high pollution levels.

According to the World Health Organization, air pollution can increase risk for stroke, heart attack, cardiovascular disease, respiratory diseases and lung cancer. Clougherty said there is also new research indicating air pollution can have a negative impact of neurocognitive processes.

According to Clougherty, the Allegheny County Health Department asked Pitt to help conduct the study because of the health risks associated with diesel pollution.

Clougherty recommended that the best way to avoid the health risks of air pollution was to avoid contributing to the problem by utilizing public transportation or biking rather than driving.

The people that are most susceptible to the effects of air pollution are generally young children who are developing lungs, older individuals or people whose immune system is already compromised.

Clougherty said that the health effects of air pollution are cumulative, and exposure as a college student could increase risk for illnesses later in adulthood.

“Don’t smoke,” Clougherty said. “Avoid secondhand smoke as much as possible, because that’s air pollution.”

Clougherty’s team at Pitt and the Allegheny County Health Department are also looking into potential policy interventions that could reduce the amount of pollution, such as changing bus routes or bus stop configurations. Clougherty said that these are only options they have discussed as potential solutions and no formal plans have been decided upon or made.

The study found that diesel pollution levels did not vary greatly across seasons but did vary by location with a higher pollution concentration in the center of Downtown than on the outskirts.

Just as Downtown has pockets of high and low emission, the rest of Pittsburgh also shows variation in pollution levels. Clougherty said this could be due to the topography — or three-dimensional aspects — of the city that creates areas where pollution can be trapped. These trappings, she said, could be one reason the center of Downtown had the highest concentration of diesel particles.

According to a release from the Allegheny County Health Department, results suggested that rush hour traffic was also a large contributor to high levels of diesel particles.

Overall, Clougherty said, the results show a large variation in distribution of diesel particles across location and time frame, although the pollution levels fell within the range seen across the country.

“The concentrations that we observed Downtown in Pittsburgh are not out of line with concentrations we’ve observed in other U.S. cities,” Clougherty said. “That said, there certainly is a substantial exposure to air pollution in our region.”