Air pollution now causes more than 4 million deaths a year. And it might be having a surprising impact on one group in particular: the 86,000 New Yorkers who commute by bike every day.

Equipped with a spandex biometric shirt and a vest holding two air quality monitors — one measuring black carbon, the other PM 2.5 — VICE News set off on a day of bike riding over New York City’s bridges, down its greenways and through its crowded rush-hour streets, to find out one thing: how much air pollution cyclists are actually inhaling.

We wanted to see what it was like to participate in “Biking and Breathing,” a Columbia University research project that aims to understand how air pollution affects cyclists’ health. Because cyclists are, on average, inhaling more air — they’re also breathing in more air pollution. The Columbia study is trying to figure out just how much more.

For the past three years, the researchers have collected data from more than 90 commuting cyclists over a period of six days. They’re measuring both air pollution as well as how much air a cyclist inhales, allowing them to estimate how much pollution reaches a cyclists’ lungs. They call this the “potential inhaled dose.”

“What really matters for health is dose, and dose is a function of two things. Number one how much air pollution is in the air. And number two how much you are breathing,” says Darby Jack, an assistant professor of Environmental Health Sciences at Columbia University.

New York City has made big strides since the 1960s, when its air was among the dirtiest in the country. But air pollution is still a leading environmental threat to the health of those in urban areas. And even low amounts of exposure to air pollution can have negative effects.

In New York, researchers aren’t trying to change the number of people commuting by bike. They ultimately hope that their findings will be used to help inform city policies on how to develop bike lanes on routes with less pollution or further away from cars.

“The best thing you can do for your health is to get a lot of exercise, and our results don't contradict that,” says Jack. “The real question from a policy point of view is — as individuals — can people make decisions that reduce risk? And can city governments put bicycling infrastructure in places that reduce air pollution concentrations and reduce risk?”

This segment originally aired July 17, 2018 on VICE News Tonight on HBO.