Millions of New York City subway commuters could be exposed to "hazardous" levels of air pollution every day after new research revealed "concerning" amounts of fine particulate matter across the system.
Across all trains and stations, the average pollution levels were roughly 10 times higher than the daily exposure guidelines set by the World Health Organization (WHO). However, some platforms and lines saw higher levels of pollution than others.
"We studied the entire subway system—all lines, all platforms," Masoud Ghandehari, a professor in the Department of Civil and Urban Engineering at New York University's Tandon School of Engineering who led the study, told Newsweek. "Every one second we took a sample. And then we took the mean concentrations on the trains and the mean concentrations across all platforms."
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In total, the average on-platform pollution concentrations were 139 micrograms per meter cubed, and the on-train concentrations were 99 micrograms per meter cubed. "For reference, the WHO limit for fine particular matter is 15 micrograms per meter cubed," Ghandehari said. "That is concerning."
However, he added that the WHO limits are based on 24-hour exposure guidelines, while commuters tend to spend roughly an hour in the subway, with roughly 10 to 20 minutes spent on the platform.
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"Nevertheless, the concentration is so much higher than the WHO guidelines," he said.
While subway systems reduce air pollution on the roads by decreasing above-ground traffic, the pollution levels in the underground systems can cause their own problems.
"Fine particulate matter, in general, is hazardous because it is so small that it can enter our bloodstream, and it has been connected with cardiovascular, respiratory and neurological diseases," Ghandehari said.
"However, most studies done on fine particulate matter—namely PM2.5, which is anything smaller than two and a half microns in diameter—involve studying fossil fuel-based particles from gasoline and diesel vehicles because those are the particles we are normally exposed to outside."
In other words, most of the studies have been done on carbon-based particulate matter. However, the majority of the particles measured in the subway system were based on iron, which Ghandehari said was likely because of the abrasion of the train car's metal wheels, breaks and rails.
However, the map shows that some platforms have significantly higher pollution levels than others. Why might this be?
"This is something that we will be looking into, but I can imagine that some of the variables may include the depth of the platform—because that will determine how well it is ventilated—or perhaps it could be a function of braking distance or that the breaking of the train is more severe, leaving residues of iron at the bottom of the tunnel," Ghandehari said.
As well as studying the pollution levels on individual platforms and trains, the team estimated the average exposure for commuters traveling in from different areas around New York City.
"We calculated the exposure by determining the home-to-work commute of individuals at 30,000 or so census block levels around New York City," Ghandehari said. "From this census data, we were able to superimpose the typical concentrations along that route."
Noticeably, they found that individuals from lower-income working communities experienced a 35 percent increased pollution exposure compared to higher-income workers, while Black and Hispanic workers experienced 23 percent higher exposure, on average, compared to white and Asian workers.
"The disparity here is less about the pollution on one line or one platform compared to another, but rather it is mostly about the duration of exposure, because most people in lower-income communities live further away so they are having longer commutes and therefor higher exposure," Ghandehari said.
However, he added that because of the high concentrations of particulate matter across platforms, including in more affluent areas, richer communities were at risk of exposure, too.
"It's one of those things that everyone should be concerned about," he said.
Not everyone agrees with these findings, though. "This recycled 'study' based on years-old 'data' has long since been debunked," Metropolitan Transportation Authority Communications Director, Tim Minton, told Newsweek.
"Every serious person knows transit is the antidote to climate change, the one reason NYC is the greenest city around, and an engine of equity for people of all communities who need an affordable, safe way to get to jobs, schools and opportunities of every kind."
Going forward, Ghandehari plans to meet with New York City officials to discuss potential solutions to reduce pollution levels across the subway system. For the time being, though, he said that the best way to protect yourself during your commute is to wear a facemask.
The full study can be read in the journal PLoS One.
Is there a health problem that's worrying you? Do you have a question about pollution? Let us know via health@newsweek.com. We can ask experts for advice, and your story could be featured in Newsweek.
Update 08/08/2024 04:39 a.m. ET: This article was update to include comments from MTA Communications Director Tim Minton.
References
Azad, S., Ferrer-Cid, P., Ghandeharim M. (2024) Exposure to fine particulate matter in the New York City subway system during home-work commute. PLoS ONE 19(8): e0307096. https://doi.org/10.1371/journal.pone.0307096
