By Claire Davenport

The New York City subway turned 120 last month. But while that longevity is cause for some celebration, a recent study out of New York University indicates the subway’s age also gives reason for worry about a little-noticed issue: the air quality on subway trains and in underground stations.

The report’s title is bland: “Exposure to fine particulate matter in the New York City subway system during the home-work commute.” But here’s the bottom line from one of the study’s coauthors, Shams Azad, a postdoctoral researcher at Columbia University’s Climate School: “The majority of underground stations and platforms are highly polluted.”

Azad said the pollution is due to iron-based particulate matter that accumulates in the subway system over time. It’s especially high, he told the Rag in an interview, on older, underground lines like the 1 train, which runs through the Upper West Side and Washington Heights. “These stations are deep underground – the particles are trapped and can’t get out,” Azad said.

The study, published in August, is based on measurements taken by Azad and his colleagues between October 2021 and March 2022. They measured the air quality on 19 different subway lines and in 429 of the 472 subway stations in the city, using handheld monitors to calculate the particle concentration in the air. The researchers rode the train lines from one end to the other, then rode the same lines in the opposite direction, getting off at every station for 10 to 15 minutes to collect air samples.

Based on their measurements, they were able to calculate how long different commuters were exposed to the polluted air. Some of the city’s most polluted stations by particulate matter concentration are the stations at West 72nd Street, 168th, and 181st on the 1 line.

“It’s not a surprise to hear,” said Rey Marte, a commuter the Rag spoke with at the 96th Street station on the 1 line. “I’ve been riding the subway since I was 16, and I can tell that the air quality is getting worse.”

Marte estimates that he spends about eight hours a week on the subway and wishes the trains and stations had more ventilation. “In the summer I ride my bike, but in the winter I have no choice but to take the train,” he said. “The city could do more to make it a nice environment.”

So should commuters worry about the quality of the air they are breathing on the subway? It’s unclear how much. According to the World Health Organization (WHO), the recommended limit for particulate matter exposure is a daily concentration of 15 micrograms per cubic meter. New Yorkers who frequently ride the subway are exposed to levels over ten times that amount.

The WHO guidelines on exposure are not specific to iron-based particle inhalation. Still, that doesn’t mean there aren’t concerning health implications, according to Scott Weichenthal, associate professor in the Department of Epidemiology, Biostatistics, and Occupational Health at McGill University, who researches the health effects of air pollution.

It’s clear, said Weichenthal, that iron-particulate matter exposure can have a negative effect on the body; less clear is the level of that effect.

“It’s sort of like comparing pollution on the subway versus from a forest fire,” he explained. “We know they’re both probably bad for you; we just don’t know the relative toxicity.”

Weichenthal said metal particulates can cause “oxidative stress.” “Our body has a sort of natural capacity to deactivate harmful chemicals,” he said. “And when you have high levels of PM 2.5 and high levels of metals like iron and copper in those particles, you’re tipping the scale in favor of more of that damage happening.”

Asked about the findings in the August report, MTA communications director Tim Minton said: “This recycled study based on years-old ‘data’ draws no conclusions on potential health issues regarding air in any subway system. Every serious person knows transit is the antidote to climate change.”

Minton also said that particles that rest on tunnel floors are cleaned by vacuum trains that rotate nightly through the system and by the mobile wash crews that clean the stations; he argued that particles in subway cars are mitigated by air filtration.

“Given that we collected data in 2021 and 2022, their comment about it being ‘recycled, based on years-old data’ is incorrect,” said Azad. “The steps taken by the MTA so far are clearly not sufficient to improve air quality effectively,” he said.

Azad suggested that commuters who are concerned by these findings can protect themselves by wearing N95 masks, which have 98 percent particulate-matter-filtration rates. He also said riders can be cognizant of higher-risk moments – air-particulate-matter concentrations are not as big a concern in above-ground stations and transit lines, and concentration increases during train arrivals and departures.

For a longer-term solution, Azad said the MTA would need to install stronger filters in train cars and ventilation at stations. Until recently, the agency’s budgeting shortfalls and Governor Kathy Hochul’s suspension of congestion pricing appeared to make such changes unlikely, though Hochul and the state are now moving forward to reinstate a congestion pricing program with a lower fee.

If you want to check your exposure to iron-based particulate matter, you can use this interactive platform Azad and his team put together.

Subscribe to West Side Rag’s FREE email newsletter here.