Makers and retailers of cycling-specific anti-pollution facemasks have a tough time with scientific studies – some academics say it's drivers who ought to be the ones wearing the masks, others say, no, it's definitely cyclists.
A Google search for the term "motorists breath in more pollution that cyclists" brings up studies that show, for example, that motorists – and their passengers – breathe in nine-times more polluted air than cyclists, even taking air-conditioning into consideration.
Many of those studies – and, boy, there are a lot of them – examine exposure. However, a new study – conducted in a leafy English town, not London – looks at what is actually breathed in.
A team from the University of Surrey’s Global Centre for Clean Air Research (GCARE) and North Carolina State University (NCSU) in the USA conducted the study to understand how four types of commuters — cyclists, drivers, pedestrians and bus-riders — were affected by small pollutant particles (from fuel combustion in engines) and large particles (from non-exhaust sources such as brake and tyre-wear).
The study was conducted in Guildford during peak commuting hours in the morning and evening, and during off-peak hours in the afternoon. The results revealed that cyclists breathed in more polluted air. This was measured via respiratory deposition doses (RDD) — this is a method that predicts the number of pollutant particles left in someone’s respiratory system.
The RDD for cyclists – and pedestrians – for finer particles was 20 per cent higher than bus passengers and 2.5 times higher than car drivers (if they have windows closed and air conditioning systems on).
The study's lead author Professor Prashant Kumar of the University of Surrey said: “Our study suggests that respiratory deposition doses need to be considered for the management of commuting exposures — and not just exposure concentration — for curtailing adverse health effects related to commuting. Even though bus riders have the highest average exposure to large particles for all times of the day, it’s pedestrians that have the highest amount of those dangerous particles trapped per unit time in their respiratory system. This story is mirrored when we talk about finer particles.
He added: “Cycling and walking benefits the health of people due to increased physical activity. However, the increased physical activity also means increased inhalation rates and hence the intake of more polluted air. Even though some cyclists experience low concentrations of particulate matter (PM), they have significant potential dose when inhalation rates and trip duration are taken into consideration."
Professor Chris Frey, co-investigator of the study from the North Carolina State University, said: “Knowledge of actual exposure to air pollution helps individuals make better choices regarding transport modes, timing and location of outdoor exercise. In the long-run, this information can help planning organisations and governments promote healthier living by including exposure prevention as a criteria for land-zoning and the built environment.
Professor Kumar added: “Better planning by moving pedestrian and cycling paths as far away as possible from roads, adding green barriers between the vehicles and passers-by to trap pollution and, wherever possible, removing cars from busy places where people walk and cycle can improve the health of many citizens."