Air pollution at Philadelphia’s 15th Street subway station ‘considerably higher’ than EPA standard

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A report from scientists at Villanova University found that the air at Philadelphia’s 15th Street subway station exposes people to a significant amount of microscopic air pollutants, well above the established standard recently set by the Environmental Protection Agency.

Scientists at the university measured the air quality at the subway station near City Hall in 2022 and recently published their results. The researchers measured the levels of various kinds of air pollutants, including a particular kind called PM2.5, so named because these are smaller than 2.5 micrometers, meaning they can get deep into lung tissue or even the bloodstream. They are smaller than specks of dust or the diameter of human hair.

The bad news is that the underground air is not great.

The Environmental Protection Agency recently set a standard for exposure to these particles, and the levels in the underground parts of 15th Street station are more than 10 times that standard, so it’s “considerably higher than the standard,” said Kabindra Shakya, an environmental scientist at Villanova.

However, he stressed that does not mean people should stop taking the subway.

“I don’t want to scare the commuters to not … use the subway,” he said. “Subways are still helping to improve the air pollution in the outdoor air. We should still keep using the subways, but we should also protect the commuters and clean it.”

He explained that the air in the subway can be cleaned, filtered and ventilated. Comparatively, if more people drive instead, then the outdoor air will be polluted, which is much harder to address.

Shakya’s previous research shows that the air quality varies across different stations, with the 15th Street station almost always having the highest concentration of this particulate matter when they did their measurements in 2018 and 2019.

It’s also unclear what the health impact of being exposed to this polluted subway air is. That will be the next phase of their research, said Aimee Eggler, a biochemist at Villanova and a co-author of the recent paper. 

“We’re taking the whole particles off the filters, and we’re exposing them to lung cells,” she said. 

The goal is to study how much stress and damage these particles will cause in lung cells because that is a marker that underlies chronic illnesses, including lung diseases associated with inhaling these particles.

The Villanova researchers said they would also like to study how the air affects commuters and transit workers, who would presumably be exposed to the air for much longer.

That is something SEPTA is interested in investigating, said Anne Tyska, the transit agency’s corporate sustainability initiatives manager, who worked with the researchers. She added that they are particularly interested in working with outside researchers because SEPTA does not have a lot of resources and “we could take the help whenever we can.”

She said she’s also interested in figuring out what works in terms of cleaning the air in subway stations: whether it’s ventilation, the design of stations, the design of train cars or something else.

“If I could make recommendations at the design phase based on some of this research and the best practices for improving air quality, I would love to be able to do that on a regular basis and really make a big impact,” Tyska said.

That will be a complex question to answer, said Keith Van Ryswyk, senior air pollution researcher at Health Canada, Canada’s federal department of health. He worked with Toronto’s public transport agency to study air pollution in their subway system, and also surveyed research from around the world to come up with guidelines for improving subway air quality.

For instance, he found that the subways in Montréal and Barcelona constantly ventilate their systems because the rubber wheels on Montréal’s system get hot, and Barcelona has a very warm climate. The constant ventilation improves the air quality, but it is also expensive.

“Whenever you’re considering improving air quality for a subway system, there’s a lot of ideas out there, but really it’s a tailoring job for a specific subway system with all the subtleties of its own design understood and integrated in the application,” Van Ryswyk said.