Cyclists (in Guildford) breathe in more polluted air than motorists finds study

A new study carried out in Guildford, Surrey, found that cyclists breathed in more pollution than motorists travelling on the same roads.

BikeBiz reports that researchers looked at four types of commuters — cyclists, drivers, pedestrians and bus-riders — to see how much they were exposed to fine and coarse particulate matter.

While they found that pollutant exposure was greater for bus passengers and motorists, the inhalation rates of cyclists and pedestrians meant that respiratory deposition doses (a measure of the number of pollutants left in someone’s respiratory system) were higher.

Past studies indicate deposition to be three or more times greater under moderate activity than when at rest.

The study found that respiratory deposition doses for cyclists for finer particles was 20 per cent higher than for bus passengers and 2.5 times higher than for car drivers (if they have windows closed and air conditioning systems on).

A ten-day study carried out last year found that exposure to fine particulate matter on Bath’s London Road was greater for a taxi driver than for a cyclist.

While high nitrogen dioxide levels were experienced by the cyclist, levels of small particulate matter from diesel fumes – associated with respiratory and cardiovascular conditions – were consistently higher for the taxi driver.

For six of the ten days, the taxi driver involved in the experiment was exposed to pollution in excess of the World Health Organisation’s (WHO) recommended limits, whereas the cyclist’s exposure always remained below.

Professor Gavin Shaddick of the University of Bath explained: “Being in a car is not like being in a sealed box.

“Winding up your windows may give you the perception that the air isn’t coming through the windows and that you might have reduced your exposure to air pollution, but the intakes for the car’s air system are at the front of the car. And the problem is, they’re generally at the level of the exhaust pipe of the car in front of you.”

However, the new study’s lead author Professor Prashant Kumar of the University of Surrey points out that exposure is not the full story.

“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, they have significant potential dose when inhalation rates and trip duration are taken into consideration."

The researchers point out that private car commutes contribute to the highest emissions per passenger, thus contributing to increased exposure of those commuting using cleaner modes.

They also suggest that pedestrian and cyclist exposures “could be further reduced by routing pedestrian and cycling paths away from heavily trafficked roadways.”

A 2016 study carried out by scientists at the University of Cambridge and the University of East Anglia modelled the risks and benefits of walking and cycling in varying levels of air pollution around the world. That study found that only in the worst one per cent of polluted cities would the ill effects of poor air quality outweigh the benefits of exercise.

According to a recent report, more than 40 towns and cities in the UK are at or have exceeded air pollution limits set by the WHO.