Subway stations near river tunnels have the worst air quality

If you’re concerned about what you’re breathing into your lungs underground—in subway platforms and stations—there’s something to your apprehension.

Last year, we reported that NYU Langone researchers found that the New York region’s subway system is the worst for air pollution in the Northeast—from D.C. to Boston. Out of 300 air samples from 71 stations taken in the morning and evening rush hours in Boston, New York City, Philadelphia and Washington, DC before the pandemic hit, New York’s subway system had the most severe levels of contamination. Hazardous metals and organic particles were found in the air.

The PATH train platforms in particular had the highest airborne particle concentration at 392 micrograms per cubic meter. To put that into perspective, the Environmental Protection Agency advises that you shouldn’t be exposed to concentrations of more than 35 micrograms per cubic meter on a daily basis, otherwise there could be serious health hazards.

In comparison, the air quality in some stations was comparable to sooty air contaminated by forest fires or building demolitions.

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Well, in a new study from NYU Langone’s Center for the Investigation of Environmental Hazards, the worst air quality across NYC subway stations are actually those near river tunnels—both MTA and PATH stations adjacent to subway tunnels that travel beneath the two rivers on the East and West sides of Manhattan.

Specifically, underground stations close to seven MTA subway tunnels that travel beneath the East River and service eleven subway lines (e.g. A, C, E, F, M, 4, 5, R, N, W, and L) in NYC were found to have higher concentrations of hazardous particles. Researchers looked at more than 100 air samples from 54 stations in total taken during rush hour.

Stations adjacent to a river-tunnel actually had 80–130% higher PM2.5 concentrations than more distant stations, the report states. Moreover, distance from a river-tunnel was the strongest PM2.5-influencing factor. They were elevated “severalfold” over ambient levels in more than 30 stations.

What is in the air? Carbon and metals like iron, manganese and chromium. These metals are likely to come from the brakes, wheels, rails and electrical power conduits in these tunnels. Ventilation, train frequency, depth below the surface and how often these tunnels are cleaned contribute to the concentration of particles, the researchers state. This finding has been called the “river-tunnel effect.”

All this being said, the health impact of these metal and carbon-rich particle mixtures on subway commuters and workers is not known. But according to past research, high levels of particles have been linked to lung and heart disease as well as an overall higher risk of death.

“Now that our results have identified key contributors to poor air quality in New York City’s underground subway stations, we have a better idea of where to improve conditions in the most contaminated areas of the transit system,” says study senior author Terry Gordon, PhD. “Increasing ventilation and scrubbing the tunnel walls and floors to remove continually recycling debris may make stations safer for riders and transit workers,” adds Gordon, a professor in the Department of Medicine at NYU Langone Health.

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