‘It’s Never Good!’: A Street-Level Look at New York City’s Air Quality

George Thurston stood at a bus stop on Manhattan’s east side, just a block from his office and the FDR Drive, a major highway in the city. He looked down at his large air monitor—a plastic tube jutted out of it, sucking in the surrounding air and measuring the amount of invisible particle pollution that surrounded him. 

Fine particulate matter, known as PM2.5, is among the most harmful pollutants, a nasty brew of chemicals and heavy metals with health impacts ranging from childhood asthma to cancer and heart disease. According to city data, long-term exposure to the pollutant contributes to an estimated 2,000 premature deaths a year, or 1 in 25 deaths in New York City.

Thurston knows all about it. A prominent air-pollution scholar, he is the director of the program in exposure assessment and human health effects at the New York University Grossman School of Medicine.

In 1987, Thurston and a colleague were the first to publish research connecting the pollutant to early death.

On a hot, humid day in mid-August, he took a walk around the city with Inside Climate News and discussed the risks that the average New Yorker is exposed to. 

Thurston’s curiosity about air pollutants extends well beyond fodder for academic research. He has carried around a small air monitor for so many years that his model has now been discontinued, he said. 

PM2.5 describes fine particles with diameters of less than 2.5 micrometers (millionths of a meter). Many of these fine particles are produced by vehicles, factories and power plants, which burn carbon-based fuels, worsening climate change—and by the wildfires, which climate change is intensifying. Some particles are so small that they can even be absorbed into the bloodstream. 

“Pedestrians waiting to cross the road are getting exposed,” said Thurston. He was standing as close as possible to the back of a bus to ensure that his air monitor could detect its emissions. Dutifully, the PM2.5 readings shot up to 27 micrograms per cubic meter. 

The World Health Organization’s air quality guidelines recommend that a person’s average exposure to PM2.5 in a 24-hour period shouldn’t top 15 micrograms. However, research suggests that even exposures below the World Health Organization’s guidelines can pose a risk. 

That’s why Thurston takes issue with the U.S. Air Quality Index, the Environmental Protection Agency’s tool for communicating health risks from outdoor pollution. The index, which incorporates measurements of many different pollutants in the air into its calculations, including PM2.5, determines that a value under 50 represents “good” air quality—illustrated by a fluorescent green color.

But according to Thurston, even when the city’s air quality shows up green on the index, “it’s never good!” 

“The bottom line is we shouldn’t be burning things. … Burning things for energy is barbaric,” said Thurston as he walked west on 23rd Street.

Air quality warnings, of which Inside Climate News counted 14 this past summer, also draw Thurston’s ire “because it gives you the impression that otherwise it’s fine.” Three of the air quality warnings this summer have been for PM2.5, largely due to the Canadian wildfires. 

One bit of good news: Thurston’s work shows that the increased PM2.5 from Canadian wildfires is less harmful than the particles emitted from the combustion of fossil fuels, the emissions pumped out of vehicles and coal or gas plants. 

While conducting research in Dhaka, Bangladesh, Thurston and other scientists found that PM2.5 from fossil fuel combustion can be much more harmful to the cardiovascular system than burning vegetation.

A more recent research paper from Thurston took an in-depth look at asthma-related hospitalizations during New York City’s so-called 2023 “smokepocalypse,” when Canadian wildfires turned the sky an alarming shade of orange. Thurston found that hospital visits occurred around the same frequency as they do on high-pollen days, which can also exacerbate asthma. A potentially important distinction is that Canadian wildfires tend to burn only vegetation, while California wildfires can also torch buildings and vehicles. 

“Wood-burning particles don’t have all the toxic [constituents],” said Thurston.  

Researchers at the Scripps Institution of Oceanography at the University of California San Diego found that wildfire-specific PM2.5 in heavily populated Southern California is up to 10 times more harmful to human health than the particles from other sources.  

Ultimately, Thurston said, people in New York City should be more concerned with their daily exposures to PM2.5 from urban pollution sources, rather than the occasional risk from Canadian wildfires. 

This summer, most air quality warnings in New York alerted residents to high ozone pollution, which happens when pollutants emitted by vehicles, power plants or refineries chemically react in the presence of sunlight. Like PM2.5, it can be harmful, especially to people with chronic conditions such as asthma.

The pollution from vehicles, especially heavy-duty trucks, has declined considerably over the last few decades as the EPA has enforced stringent regulations on polluting diesel-powered vehicles. Trucks manufactured after 2007 must carry diesel particulate filters, among other pollution-reduction measures.

“The only reason our air has gotten so clean is because of regulations,” Thurston said. “But I know everybody hates them.” 

The regulations ultimately pay for themselves, he said, with the cost of lives saved. Truck traffic is a significant issue in New York City, where the destinations of high-emission vehicles are often in low-income neighborhoods and communities of color. 

As he continued down 23rd Street, Thurston was periodically “zapped,” as he put it, when passing food trucks, which emit high levels of PM2.5. Near one small food truck, the concentration of PM2.5 shot up from the low teens to 45 micrograms per cubic meter on Thurston’s monitor.

But his monitor registered the largest number of PM2.5 particles on the city’s greenest mode of travel—the subway. 

As he scurried cheerfully down the stairs at 23rd Street Station, PM2.5 concentrations rose from just below 20 to 40. Then they more than tripled, soaring to a whopping 133 micrograms per cubic meter as he waited for the 6 Train to Grand Central Station. 

“We don’t really know how harmful these particles are,” said Thurston. 

That’s because they’re not like your average PM2.5.

Last year, Thurston co-authored a study on particle pollution in the city’s subway system, finding that short-term PM2.5 concentrations in the stations were roughly four times higher than the U.S. EPA’s 24-hour average outdoor air standard of 35 micrograms per cubic meter.

But the study also questioned whether the EPA standards could be applied in this case, because the pollution composition included much higher levels of iron than in outdoor air—these standards are usually used to analyze PM2.5 pollution in the context of burning fossil fuels or vegetation. Much of the particle pollution in the subway comes from wear and tear on the metal rails, as well as the use of train brakes. 

Construction trains, used for maintenance and other tasks such as track replacement, are diesel-powered to ensure uninterrupted service in the event of power outages. That can contribute to underground pollution, though these trains are slowly being phased out by more environmentally-friendly locomotives. The stations are poorly ventilated, Thurston said, keeping the particles low to the ground. 

But the air inside the trains is usually purified. As Thurston entered the 6 Train, he saw real-time evidence of this. The PM2.5 concentration decreased quickly to below 30 micrograms per cubic meter. 

Outside, in the busy intersections that surround Grand Central Station, the concentration shown on Thurston’s air monitor stayed fairly steady at around 12 micrograms per cubic meter, going up slightly when the monitor was downwind of idling cars and buses at a traffic light. 

Idling, Thurston said, releases a lot of these particles. He worried aloud that the city’s regulations, which stipulate that no vehicle can idle for longer than three minutes while parking, standing or stopping, are not enforced often enough—and that people don’t understand the risks of constant exposure. 

Before heading back to his office, Thurston took a short detour up to 60th Street—the end of the city’s relatively new congestion pricing zone—to see if there was increased traffic, and thus higher levels of PM2.5. But he found little difference between the measurements there and near Grand Central Station. Congestion pricing has been shown to meaningfully reduce the amount of traffic in downtown Manhattan. 

By the time Thurston finished the 20-minute walk from the subway to his office, the sweltering heat was getting to him. The sun was beating down on this summer day, and Thurston had ventured out without a water bottle. Heat, he noted, can exacerbate the health impacts from air pollution. 

“It’s a stress on the body,” he said. 

When it’s humid, sweating doesn’t work as well because evaporation is harder when the air is already so full of water. 

But no matter the temperature, air pollution can have health impacts, and Thurston really wants people to be aware of that. In the city, residents face those consequences daily, even when there’s no air quality warning. 

“We’re surrounded by fossil fuel combustion,” he said. “It’s always somewhat of a risk.”