People commuting via subway systems in major US cities – particularly New York City, Philadelphia, Washington DC, and Boston (which are the four that make up the majority of the country’s underground transportation system) – are being exposed to unsafe amounts of air pollution. A research team led by the NYU Grossman School of Medicine found that the riders encounter particle quantities well above safe levels, with those from New York and New Jersey being subjected to the highest levels.
The study measured the air quality of 71 subway stations in those four cities during the morning and evening rush hours. Every city had stations with concentrations of airborne particles at least double that of the air outside. The researchers say the tiny airborne particles are probably caused by the friction between train wheels and rails or thrown up by train brakes.
David Luglio, the study lead author and a doctoral student at NYU Grossman School of Medicine, said in a statement:
Our findings add to evidence that subways expose millions of commuters and transit employees to air pollutants at levels known to pose serious health risks over time.
The most polluted subway system was New York City’s. The Manhattan station ‘Christopher Street,’ which helps connect New York with New Jersey, had the highest level: 1,499 micrograms per cubic meter. It was about 77 times higher than the air pollution outside (above-ground). That’s like breathing in the air surrounding a building demolition or a wildfire. The team calculated the health risk for someone commuting to and from Christopher Street regularly and found that it increases their chances of an adverse cardiovascular event by 10%.
Terry Gordon, a study co-author and professor at NYU Langone Department of Environmental Medicine told The Guardian:
As riders of one of the busiest, and apparently dirtiest, metro systems in the country, New Yorkers, in particular, should be concerned about the toxins they are inhaling as they wait for trains to arrive.
It was the worst pollution ever measured in a subway station, higher than some of the worst days in Beijing or Delhi. It just wasn’t believable. My colleague went down there, and his airways were feeling tight after an hour or so.
The Philadelphia subway system was the least polluted overall. Still, its 30th Street station was among the most polluted stations, along with Broadway in Boston and Second Avenue in New York City. And although Philadelphia was comparatively cleaner, it still breached the limit beyond which severe health hazards are risks.
Millions of people use the subway systems to get around. The country’s largest system, New York’s MTA, shuttled 5.5 million people across the country daily in 2019.
The MTA says the research isn’t through but that it’s looking at new air filtration systems for the subway anyway because its customers’ safety is its highest priority.
Tim Minton, the MTA’s communications director, said:
We have conducted previous air quality testing on subway trains operating in our system and found no health risks; however, we will thoroughly review this study as the safety of customers and employees is always our highest priority. The MTA is currently piloting technology solutions due to pandemic-related innovation, which will further enhance filtration in subway cars.
More research is essential to pinpoint the exact health impact upon riders and determine the pollution source. They also want to understand why certain stations are so much more polluted than others and the exact pollution sources – which can range from dust whipped up from the remains of dead rodents to the exhaust given by diesel locomotives.
