Subway Air Pollution Worse in Stops Near Underwater Tunnels

It turns out we would be wise to keep wearing masks in the subways, no matter what happens to the Covid-19 virus.

Because as resilient as that virus is, it is only one of the hazards of breathing while riding the subways, a new study reminds us. The study confirms earlier research that subway air is heavy with tiny particles of metal and other pollutants, and for the first time tracks much of this grit to the deep tunnels under the river.

“A key health burden question for commuters and transit workers is whether subway air is safe to breathe,” the researchers, from NYU’s Grossman School of Medicine, wrote in a journal called Transportation Research.

Like a hurried strap-hanger at rush hour, The MTA pushed back. “We have conducted previous air quality testing in the subway system and found no health risks,” said a spokesperson, Michael Cortez, “However, we will thoroughly review this study as the safety of customers and employees is always our highest priority.”

At issue are pollutants know as PM 2.5. That is, inhalable particulate matter smaller than 2.5 micrometers, about 30 times smaller than the width of a human hair. The grinding of steel wheels on steel rails, electric transmission rails and brake shoes spew these particles into subway air.

The new study suggests these particles pool in the tunnels under the rivers and are then pumped by passing trains into the system, with the closest stations getting the heaviest doses.

“Exposure to fine particles can cause short-term health effects such as eye, nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath,” according to the New York State Health Department, which warned it “can also affect lung function and worsen medical conditions such as asthma and heart disease.

Scientific studies, the health department said, have also linked increases in daily PM2.5 exposure with increased respiratory and cardiovascular hospital admissions, emergency department visits and deaths, reduced lung function and increased mortality from lung cancer and heart disease.

That’s the bad news. The good news is that reduction in PM2.5 in the air we breath has been one of the triumphs of modern environmental regulation. Cleaner cars and lower emissions from furnaces and factories-- and even more mass transit use -- have produced a 37 percent reduction in PM2.5 nationwide since 2000, 43 percent in the Northeast.

This has brought exposure levels above ground consistently below the federal standard of an average of 12 micrograms of particulates per cubic meter of air over the course of a year and 35 micrograms per cubic meter in any 24 hour period.

“New York city is cleaned up,” said Professor Terry Gordon of NYU’s Grossman School of Medicine.

But Professor Gordon and colleagues at the Center for the Investigation of Environmental Hazards have been looking at how particulate pollution still builds up in poorly ventilated corners of the city, from hookah bars to food carts and restaurant kitchens.

Studies he has conducted of mass transit in a number of cities, including New York, found levels of PM2 in most subway systems considerably higher than the federal standards, although also widely varied from station to station within the systems.

Indeed, one of the most polluted stations in the entire world, said Dr. Gordon, was beneath Cristopher street in Greenwich Village, a stop on the PATH line from New Jersey. At the other end of the Hudson River tunnel its counterpart Newport stop in New Jersey was just as bad.

“We couldn’t believe it was so high,” Gordon recalled.

A light went off, Gordon said. Maybe it was the stations proximity to the Hudson River Tunnel? “If Newport and Christopher, which are on each side of the river, were the worst, is there something going on with the tunnels underneath the rivers?”

So Dr. Gordon and his team went back into the subways to monitor particulate matter at stations on either side of the East River Tunnels.

“Stations neighboring river tunnels had 80% to 130% higher concentrations of potentially dangerous particles in the air compared with stations only two or three stops further away from rivers,” the researchers reported.

Lex and 59th St R Train Stop Among Worst

For example, Lexington Avenue and 59th street on the R train just before it heads to Queens had a PM2.5 reading of 224 micrograms per cubic meter. First avenue on the L arriving from Brooklyn was 108. Bowling Green on the Lexington 4 and 5 lines was 233 and Fulton Street on the A and C was 231. At Lexington Ave and 53d St before the E heads to Queens the count was 203. East Broadway on the F train measured 114.

These numbers are all far above the federal standards, but the MTA rejected any comparison. “This study tested a hypothesis by only taking samples for short periods, at the most active time of day, which is not an accurate comparison to EPA standards for daily exposure limits,” the MTA spokesman said.

“The question is, does the short term exposure to really high concentration affect people?” said Dr. Gordon. “I’m still going to ride the subway when I need to. I would wonder if someone with asthma or cardiovascular disease might be more susceptible to effects of these high particulate concentrations.”

Transit workers, of course, spend far more time exposed to the air in the subways. “Nothing is more important that the safety of our members,” said a spokesman for local 100 of the Transport Workers Union. “We are evaluating the report and consulting with experts.”

The MTA could reduce particles in the air by cleaning tunnels and improving ventilation, although Dr. Gordon is skeptical they would undertake such efforts giving their denial of the problem and the systems pressing fiscal shortfalls.

“If someone asked me what can an individual commuter do? I think a mask is about the only thing they can do,” Dr. Gordon said. “So wearing the mask for Covid has the additional co-benefit that it is going to protect you from the particles in the air that I’m studying.” A snug N-95 mask filters out 95% of those particles, Dr. Gordon said, and even a surgical mask stops 40 to 70 percent of particles. “So they work,” he said.

“The long term goal,” he added, “might be for riders, straphangers to get together to put pressure on the transit authorities of the major cities to clean up the air.”