Research shows New York City subway riders are breathing dangerous air

Travelers on the New York City subway breathe dangerous air, with Black and Hispanic commuters exposed to higher levels of pollution, a new study finds.

Researchers from New York University discovered that the average subway platform four times fine dust pollution (PM2.5) exposure level considered safe by the Environmental Protection Agency over a 24-hour period, and nine times the World Health Organization exposure guideline.

The researchers note that although commuting accounts for only part of the day, subway travel accounts for a significant portion of daily PM2.5 exposure.

“At that size, these particles penetrate into the lungs, and small particles have been shown to cause cardiovascular, respiratory and neurological problems,” said Masoud Ghandehari, the lead researcher and a professor of urban systems engineering at New York University. “We have 5 million riders a day. Imagine the human impact one person can have in one day on the New York City subway system.”

The burden of air pollution falls disproportionately on low-income people and communities of color, both above and below ground. By looking at census block data for race and income, researchers found that low-income New Yorkers and those living in predominantly Black and Hispanic communities have longer, more frequent commutes. That, in turn, leads to higher exposure to dangerous air pollutants. The study found that Black and Hispanic workers endure PM2.5 levels that are 35% and 23% higher, respectively, than Asian and white commuters.

“Most of the jobs are in financial districts in New York City, (such as) midtown and downtown Manhattan,” Ghandehari said. “Those who are lower-income tend to live farther away from these job centers. So their commute time is ultimately longer, which means their exposure is going to be greater.”

The researchers found a staggering concentration of iron in the fine particles they analyzed. That’s largely due to wear and friction from the metal wheels, brakes and rails of trains, they said. Older, deeper, busier stations with poor ventilation had higher concentrations of PM2.5.

“All the pollutants brought in from the outside air are captured and recirculated,” said Kabindra Shakya, a assistant professor of geography and the environment at Villanova University who was not involved in the study. “Above ground, there’s more opportunity for dispersal, wind speed to carry it away and clean it, whereas (below ground) it collects with less ventilation.”

In 2020, Shakya and his team found it that air pollution levels in Philadelphia’s subway systems were about four times higher than above ground. They also found that stations with less direct access to the outside air had higher concentrations of particulate matter.

He described the risk to people on short journeys as “minimal”, but added: “I would stress that professionals, such as metro workers or the vendors who work (there), are at greatest risk.”