A new study shows subway users in New York City are exposed to dangerous levels of pollution while commuting.
What's happening?
Researchers found that the air at NYC subway platforms has, on average, four times the level of fine particulate matter (PM2.5) as would be deemed safe by the Environmental Protection Agency over a 24-hour period, the Guardian reported. The level of pollution exposure is also nine times more than the suggested limit set by the World Health Organization, per the news outlet.
While these guidelines by the EPA and WHO refer to exposure over a 24-hour period, and commuting time is only part of a day, commuters receive a significant portion of their daily exposure to PM2.5 while riding the subway, the Guardian detailed.
Per the report, communities of color and low-income commuters are disproportionately affected by the dangerous air quality. Many jobs in NYC are located in the financial districts, which are farther from low-income communities and majority Black and Hispanic communities, causing workers from those communities to commute for longer periods.
Researchers found that the PM2.5 levels for Black and Hispanic employees were 35% and 23% higher compared to Asian and white people, per the Guardian.
The study also showed an extremely high concentration of iron present in the subway air particles, largely due to the friction among trains' metal wheels and brakes and rails.
In addition, pollution from the outdoors that enters the subway at "older, deeper, busier" stations with poorer ventilation becomes trapped and is recirculated, contributing to the high levels of PM2.5.
Why is particulate matter important?
While mass transit gets cars off the roads and hugely contributes to an overall reduction of particulate matter and other pollution that rises into the atmosphere, trapping heat that leads to climate change, it's still important that the air inside a subway system is safe enough to breathe.
Particulate matter is a mix of varying pollutants. The descriptor 2.5 indicates the individual particles are less than 2.5 microns in diameter. Particulate matter that is 10 micrometers or smaller is generally considered inhalable and can cause negative health effects, per the EPA, with PM2.5 posing the greatest risk.
"At that size, these particles penetrate the lung, and it's been shown that small particles cause issues with cardiovascular, respiratory and neurological diseases," Masoud Ghandehari, the lead researcher of the study and a professor of urban systems engineering at New York University, said, per the Guardian. "We have 5 million riders per day. Imagine the human impact one may be having in a single day in the New York City subway system."
The California Air Resources Board warns that infants and children inhale more air per pound of body weight compared to adults, putting them at higher risk of adverse health effects from exposure to PM2.5.
Particulate matter can also negatively affect the climate and ecosystems by contaminating water, soil, and plants, according to the CARB.
What's being done about air pollution?
MTA Communications Director Tim Minton said "particles that may rest on tunnel floors are mitigated by vacuum trains that rotate every night through the entire system" as part of a statement to The Cool Down to address the concerns, which he dismissed as making "no effort to wrestle with the reality that New York City ambient air" has its own starting particular matter.
"This recycled study based on years-old 'data' draws no conclusions on potential health issues regarding air in any subway system," he said. "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."
Minton also alleged that "the study itself is not authored by health experts and takes no position on health impacts," and that "particles in subway cars are mitigated by MERV-8 and MERV-9 filters in all train cars ... that turn over fresh filtered air every 3-4 minutes — filtration and turnover comparable to hospitals and offices."
Air pollution — in various forms — is a problem everywhere, but researchers around the world are devising new strategies to combat this issue.
In Texas, experts found a way to capture carbon from the atmosphere and store it. A team in Indiana developed technology to stop pollution at its source. And Bill Gates backed a startup that turns carbon pollution into delicious butter.
Editor's note: This story has been updated to add commentary from MTA Communications Director Tim Minton.
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