Next time you pedal to work instead of driving or hopping on the subway, you might want to pick a longer route. Cycling on congested city streets or suburban thoroughfares -- even if faster -- boosts the amount of toxic chemicals absorbed by your body, according to a new study.
The study's authors are careful not to discourage urban cycling. Instead they suggest choosing routes away from busy traffic or industrial areas.
"It is still better to be bicycling to get the health benefits from physical activity, even with the amount of (air pollution) exposure," said Alex Bigazzi, professor of civil engineering at University of British Columbia in Vancouver. "However it is useful to know that your body levels of toxicants will be lower if you can chose a lower traffic route. You might have to go a little out of your way to do that."
Bigazzi and colleagues at Portland State University used special breath analysis devices on three cyclists riding the streets of Portland for 20 to 30 minutes daily. After compensating for ambient pollution levels, the cyclists rode through heavy traffic, light traffic and side streets or bike paths. Not only was the exposure two or three times greater for the cyclists on the busy roads, so too was biological uptake of volatile organic compounds, the kind spewed out by cars and trucks.
To estimate how these chemicals were getting into the subjects' bloodstream, Bigazzi used biomarkers of the compounds found in the subjects' breath. The study was published recently in the journal Environmental Science & Technology.
Even though Portland is a relatively clean place (all that rain) and has embraced bike culture more than most American cities, Bigazzi said the chemicals were worrisome.
"We are not exceeding (federal workplace health) standards, but they were high enough to see some negative impacts for repeated exposures," Bigazzi said.
The Portland study backs up similar results from a 2012 experiment in London. That study tested for particulate matter, tiny bits of carbon, dust and soot spawned by the combustion process that become lodged in the airways and can lead to asthma, heart attacks, stroke and other health effects.
"Exercising along heavily polluted roads will give you a higher dose of pollution," said Jonathan Grigg, professor of pediatric respiratory medicine and Queen Mary University of London. "But everyone should have a right to be in an area where you are not going to have that effect. We think it is good for you, if you chose to cycle. It should be your government to allow you to do that and not get exposed to a higher level of pollution."
Grigg's study measured carbon particles directly that become lodged in white blood cells coughed up from the cyclists lungs. His study compared 14 cyclists to 14 subjects who walked to work or took public transit.
Grigg said the Portland study is "interesting preliminary data" but needs to be expanded and use a more direct form of measuring pollution uptake by the body.
Janice Nolen, vice president for national policy at the American Lung Association, says that it's not only cyclists that are harmed by air pollution. So, too, are people who live near busy highways.
Passenger vehicles will get cleaner in 2017 model year, "but there are still a lot of them out there that are high polluters, diesel especially," Nolen said.
A 2013 study by MIT found air pollution causes about 200,000 early deaths in the United States each year. Emissions from road transportation are the most significant contributor, causing 53,000 premature deaths, followed closely by power generation, with 52,000.
"There's a lot of ways besides biking that you can get exposed to these high levels of pollution," Nolen added.