Study on Wheels

A new study investigates the dangers of air pollution for urban cyclists

March 30, 2015

With spring here, urban cyclists are back in the saddle, burning calories and enjoying the outdoors. Every year, more people join the pack, thanks to the proliferation of bike paths and bike-share programs like New York’s Citi Bike. But is cycling in the city as healthy as people think?

According to Darby Jack, assistant professor of Environmental Health Sciences at the Mailman School of Public Health, some city cyclists may be exposing themselves to unhealthy amounts of air pollution. To test his hypothesis, Jack is joining with WNYC Radio this spring to recruit riders for a study on wheels.   

The idea grew out of a pollution study in Ghana where Jack used a device called a micoPEM to measure tiny airborne particles from indoor cooking stoves. Pollutants from these stoves were linked to low birth weights, heart attacks, and lung cancer.  

Back in New York, he wondered if the same measurements could be applied in a different context. “As I was riding my bike around the city, I wondered how much air pollution I was taking in.”

Most methods to assess pollution exposure measure concentrations in the air. But even if the air monitoring equipment were attached to the bicycle, Jack still wouldn’t have the answer to his question. That’s because the method would measure concentrations in the air and not the actual dose of pollution inhaled by a cyclist. When we start to get tired, our breathing speeds up. The “inhaled dose” of pollution, in other words, is a function both of the concentrations of pollution and of the volume of air inhaled. Even Jack found that his breathing increased by a factor of ten while he was commuting from his home in Brooklyn to the Mailman School in Washington Heights. 

Sensors in Motion

To account for these factors and to assess how they affect the cardiovascular system, Jack and Steven Chillrud, a professor at Columbia’s Lamont-Doherty Earth Observatory, assembled a sophisticated blend of technologies: GPS to log speed and location; microPEMs to measure fine particles; microAeths to measure black carbon from fossil fuels; biometric shirts that record heart rate and breathing volume; and ambulatory blood pressure monitors to detect small changes resulting from air pollution exposure.  

In an initial testing phase, he recruited a small group of bicycle commuters to wear the gear on and off their bicycles to compare levels during high exertion with those at rest indoors.

For one of Jack’s volunteer commuters, Mailman School staffer Sean Campbell, this study inspired some high-tech consciousness-raising for a low-tech endeavor.

“Naturally I assumed I was healthier than the throngs of people taking the subway to work,” said Campbell. “I’m interested to find out if air pollution is putting my health at greater risk than riding the L train.”

Preliminary data points to the hazards of riding hard in Manhattan’s “street canyons,” where pollution from traffic can be high.  

By contrast, the Hudson River Greenway is relatively pollution-free, even though it’s only a few yards from the West Side Highway. “Even a small separation from traffic can make a substantial difference,” Jack explains.

No matter where you are, when there’s heavier traffic like at rush hour, you breathe in more pollution. “If you feel like you just got a big lung full of air pollution, you probably did,” said Jack.  

Recruiting on the Radio

In what may be a first for Mailman School research, Jack is working the data news team from WNYC to recruit “citizen scientists” for the first phase of a larger cycling study, supported by a grant from the National Institutes of Health. The cyclists will collect data all over the city for analysis by the Mailman team.

“We’ve been meeting with the data science team at WYNC and they’re keen to report on the research and also help with some data visualization. Our aim is to put the pieces together into a [pollution] map that can be useful to cyclists.”

The collected data has the potential to help New Yorkers plan their bike rides to steer around areas known to be extra-polluted.  What’s more, the research could help city planners decide where bike lanes are situated and inform the creation of amenities like the Greenway that minimize exposure, explains Jack. “We’re thinking of it as a policy input where this information leads to the design of safer infrastructure.”

As to whether urban cycling is bad for your health, Jack says it’s unlikely, even after accounting for air pollution levels seen in the U.S. “I expect you’d still see a huge net benefit to cycling.”

Time to saddle up, and hit the road.