Could cycling in a city be hazardous to your health?
Most cyclists have been there: peacefully pedaling one minute and sucking bus exhaust the next. In the moment, all you can do is keep riding and shrug off the blast of smoke. But now a growing body of research suggests breathing this pollution can have both short-term and long-term health consequences.
A team of researchers from Columbia University has started using a suite of state-of-the-art personal monitoring devices to gather more details about how air pollution affects cyclists’ health.
The new study—a joint undertaking by scientists in the Mailman School of Public Health and the Lamont-Doherty Earth Observatory—aims to show minute-by-minute health and pollution data.
The researchers have equipped volunteer bike commuters with a skintight biometric shirt, a mesh vest stocked with air pollution monitors, a location tracking system that liaises with smartphone GPS software, and a blood pressure monitor. Combined, the instruments will characterize exactly where a rider inhales pollution and how his or her lungs and heart respond.
“We’re really trying to quantify the health impacts of commuting by bicycle in a dense urban setting,” says Darby Jack, an environmental health scientist at Columbia University and part of the study’s brain trust.
In New York City alone, health officials estimate that fine particulate matter (known as PM2.5) contributes to nearly 2,000 premature deaths and more than 6,000 hospital visits per year. The young and old are particularly susceptible, as are people who suffer from asthma and other respiratory disorders or heart disease.
“We have internal combustion engines that emit particles, we put them out a tailpipe, and then we drive along our sidewalks. And we sort of emit this stuff right into our breathing zones,” says Arden Pope, a professor of economics and an epidemiologist at Brigham Young University who is not involved in the Columbia study.
As these particles—particularly the fine ones—spew from tailpipes, they are inhaled and accumulate in lungs. Most of these particles are black carbon, but vehicles also discharge nitrogen oxides and polycyclic aromatic hydrocarbons (PAH).
Research has shown that long-term exposure to these pollutants increases the risk of heart and lung disease, and short-term exposure can trigger heart attacks.
The problem is amplified by exercise. During workouts, respiration increases and more air enters the lungs. Jogging, for example, can increase the volume of air by three to four times, and strenuous exercise can push the volume even higher. All this extra air also brings more pollutants into the body.
This creates a conundrum for bike commuters in the city: At what point does exercise hurt your health more than help it?
It is generally thought that the benefits of exercise outweigh the hazard of air pollutants, and a recent study suggests this is true in “the vast majority of settings.” In a city like New York, with background PM2.5concentrations below the global average, a healthy person without heart or lung problems would need to cycle for hours and hours a day before the adverse impacts of pollution outweigh the health benefits of exercise. At that point, the only health effect you’re likely to suffer is a sore bum from riding all day.
However, Jack says looking at background concentrations alone may not tell the full story. “You can really underestimate the exposure for folks exercising in urban settings,” he says. Pollution varies by location—it is not static or evenly distributed. And as we move through a city, exposure differs depending on the setting.
“Using a single number for PM2.5 to represent an entire city isn’t really true exposure,” explains Patrick Ryan, an epidemiologist at the Cincinnati Children’s Hospital Medical Center who is not involved in the research. “We know that you interact with air pollution over the course of the day … and it really changes your exposure.”
Furthermore, exposure fluctuates based on our level of physical activity. Cranking up a hill behind a belching garbage truck is much different than a casual cruise on the Manhattan Waterfront Greenway.