City cyclists breathe in twice as much soot: study

New York (Reuters Health) - Urban cyclists may be exposed to more than twice as much black carbon from vehicle exhaust as pedestrians, a small new study suggests.

By examining airway cells in sputum samples from ten people, researchers in London found black carbon levels were 2.3 times higher in the five cyclists compared to the five pedestrians.

Black carbon, a byproduct of gasoline and diesel fuel combustion, is associated with decreased heart rate variability, heart disease and asthma, among other adverse effects.

“We know that exercise provides a health benefit, but exercise in less polluted areas would be preferable,” researcher Dr. Chin Nwokoro from Barts and the London School of Medicine told Reuters Health by email.

“There is still uncertainty whether at-risk individuals, for example those recovering from a heart attack, should regularly cycle on heavily used roads,” Nwokoro said. “We will have more certainty about recommendations for this when our full study is published.”

Nwokoro and his colleagues presented their data at the European Respiratory Society’s annual congress in Amsterdam on September 25.

There was no statistically significant difference between cyclists and pedestrians in any other factor, including average age, distance from home to major roads, lung function or even the amount of time spent exercising.

The researchers’ working theory to explain the soot increase is that cyclists breathe more deeply and faster than pedestrians while they are riding in traffic.

“This is an interesting study,” said Dr. Daisy Janssen, a clinical researcher at Proteion Thuis in Haelen, the Netherlands, who was not involved in Nwokoro’s project. “Further studies are needed to identify the consequences of this finding and the need for low-pollution cycling routes.”