Take the Road Less Traveled — For Your Health

Black carbon exposure peaks may be lower on quieter streets than on main roads


When choosing your route to work, you may want to consider avoiding the busy streets.

A new study from England found that walking to work via quieter side streets rather than main roads may reduce the risk of exposure to peaks in harmful air pollution, especially black carbon (BC).

BC is a component of air pollution that is formed through the incomplete combustion of fossil fuels, biofuels, and biomass and is emitted as soot. Primary sources of BC include emissions from diesel engines, wood-burning stoves and fires.

Soot is made up of very fine particles, which can easily be inhaled. Inhalation of BC is linked to health problems like respiratory and cardiovascular diseases, cancer and even birth defects.

"We know that short-term exposure to black carbon is associated with increased hospital admissions due to respiratory symptoms, and that long-term exposure is associated with exacerbation and increased prevalence of asthma," said lead study author Lee Koh, a researcher at the Blizard Institute at Queen Mary University of London, in a press release. "Since London is one of the most polluted cities for black carbon in Europe, ways that people might be able to reduce their own exposure are of interest, and we wanted to see whether walking quieter, side-street routes might help to do this."

For this study, Koh used a hand-held monitor to measure BC levels while taking a walk through London's main roads. She then compared the results to readings taken while following a quieter route.

Walking the busy route six times yielded BC readings between 3,339 and 6,995 nanograms per cubic meter every five minutes.

By comparison, walking the quieter routes six times yielded BC readings between 2,555 and 5,854 nanograms per cubic meter every five minutes.

To put these figures in perspective, the UK's Daily Air Quality Index recommends not exceeding 35,000 nanograms per cubic meter of BC exposure in 24-hour period.

There was also a significant difference between the peaks of BC exposure between the two routes.

While there were no peaks in BC exposure on the quieter route, there were three occasions when BC levels exceeded 10,000 nanograms per cubic meter on the main route.

"The peaks are when much higher levels of pollution are present," Koh said. "For example, when you stop to cross a busy road and so you are subject to a higher level of pollution compared to when walking away from the traffic."

This study was presented Sept. 27 at the European Respiratory Society's 2015 International Congress. Research presented at conferences may not have been peer-reviewed.

Information on funding sources and conflicts of interest was not available at the time of publication.