A new study from New York University Grossman School of Medicine found high levels of air pollution in subway stations belonging to some of the country’s largest transit systems.
The NYU researchers sought to assess the air quality in subway stations in major Northeastern cities. Conducted before the COVID-19 pandemic threatened the lungs of transit workers and commuters, the study looked at 71 stations across 12 transit lines in four cities — New York City, Boston, Washington, D.C., and Philadelphia.
They studied the composition and concentrations of minuscule, lung-damaging particulate pollutants known as PM2.5. According to the U.S. Environmental Protection Agency, one PM2.5 particle is at least 30 times smaller in diameter than a strand of human hair. This makes it easy to inhale deeply into the lungs and can lead to serious health problems such as heart attacks, aggravated asthma, and decreased lung function.
The NYU researchers monitored air quality at six underground stations along the Market-Frankford Line and eight stations along the Broad Street Line in 2015, during morning and evening rush hours.
They found the SEPTA lines had smaller average real-time concentrations of the pollutant than other transit lines, measuring the concentration of PM2.5 at 39.2 micrograms per cubic meter. The safety standard for a 24-hour period set by the EPA is 35 per cubic meter.
The PATH service, which serves New York City and part of northern New Jersey, had concentrations 10 times as high as Philadelphia at 391.9 per cubic meter. New York City Metropolitan Transportation Authority followed with 250.5 per cubic meter. The pollution levels found exceed recommended exposures, falling into an unhealthy range, according to the EPA.
Further analysis of air samples taken in stations revealed iron and organic carbon, a chemical produced by the incomplete breakdown of fossil fuels or from decaying plants and animals. Philadelphia was not included in this analysis, however.
Although iron is largely nontoxic, some forms of organic carbon have been linked to increased risk of asthma, lung cancer, and heart disease, the study authors wrote.
Terry Gordon, a professor in the Department of Environmental Medicine at NYU Grossman and a senior study author, said trying to eliminate the pollution completely is farfetched. Still, there is action agencies can take.
“Once you find out what the sources are, see if there’s something you can do,” he said. The professor suggested using maintenance trains powered by batteries instead of diesel, improving ventilation systems, or using different materials on their materials.
“You’re not going to get rid of the rails or the wheels or the electrification system, et cetera, but there are things they can do,” said Gordon.
Gordon said that further research is needed to assess potentially higher risks for transit workers who spend far longer periods of time in the stations than riders.
The study, published in the journal “Environmental Health Perspectives,” comes at a time when SEPTA is working to bring riders back to their systems after the COVID-19 pandemic led many riders to avoid the crowds of buses and trains. Gordon said the timing is coincidental and not intentional.
The authority announced in December a partnership with Drexel University aimed at improving efforts to stop the spread of COVID-19 on public transportation and kicked off a campaign last month that encourages riders to wear masks. They also delayed fare increases until at least July.
SEPTA spokesperson Andrew Busch said agency officials will review the research. “We’ll certainly take a close look at this study … to see if there’s things that we can learn,” he said.
Busch highlighted the authority’s ventilation improvement efforts and said SEPTA is always seeking technologies that will “improve the health and safety of our riders and employees.”