People who cycle through London and other major cities have higher levels of black carbon in their airway cells, claims new research, presented at the European Respiratory Society’s Annual Congress in Amsterdam yesterday. The study suggests that cyclists inhale more black carbon than pedestrians. Motorists were not included in the study.
There is increasing evidence that inhalation of black carbon particles is associated with a wide range of health effects – including heart attacks and reduced lung function.
The researchers, led by Professor Jonathan Grigg from Barts and the London School of Medicine, aimed to identify whether the way adults commute to work affects their exposure to black carbon. Specifically, they tested the hypothesis that cyclists have higher personal exposure to black carbon.
To test this theory the study compared the lung dose of black carbon in cyclists and pedestrians. To measure lung dose the researchers sampled a lower airway cell called the airway macrophage – a specialised cell that sits on the airway surface and ingests foreign material.
The researchers collected sputum samples from five adults who regularly cycled to work in London and five pedestrians and analysed the amount of black carbon found in their airway macrophages. All participants in the study were non-smoking healthy urban commuters aged between 18 and 40 yrs.
The results showed that in this (scientifically tiny) sample, cyclists have 2.3-times more black carbon in their lungs when compared with pedestrians.
Dr Chinedu Nwokoro, one of the researchers of the study and an active cyclist, said: “The results of this study have shown that cycling in a large European city increases exposure to black carbon. This could be due to a number of factors including the fact that cyclists breathe more deeply and at a quicker rate than pedestrians while in closer proximity to exhaust fumes, which could increase the number of airborne particles penetrating the lungs. Our data strongly suggest that personal exposure to black carbon should be considered when planning cycling routes.”
This may be one conclusion: another might be for cities to limit the amount of motorists allowed to pollute at any one time.
And motorists should not assume that closed windows and air-conditioning systems are protection from noxious gases and particulates created by driving. Other studies have shown that motorists inhale motorised traffic pollution, and don’t exhale it as fast or as deeply as those exercising, such as pedestrians and cyclists.
One study said:
"It has frequently been claimed that cycling in heavy traffic is unhealthy, more so than driving a car. To test this hypothesis, teams of two cyclists and two car drivers in two cars were equipped with personal air samplers while driving for 4 h on 2 different days in the morning traffic of Copenhagen. The air sample charcoal tubes were analysed for their benzene, toluene, ethylbenzene and xylene (BTEX) content and the air filters for particles (total dust). The concentrations of particles and BTEX in the cabin of the cars were 2–4 times greater than in the cyclists’ breathing zone, the greatest difference being for BTEX. Therefore, even after taking the increased respiration rate of cyclists into consideration, car drivers seem to be more exposed to airborne pollution than cyclists."