Pedestrians ‘at highest risk’ from air pollution

Cyclists and pedestrians are twice as likely to keep dangerous particles in their respiratory systems than car drivers, a new study by researchers at the University of Surrey has suggested.

Published in the journal Climate and Atmospheric Science, the study sought to understand how 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 on their daily journeys.

The study looked at the exposure of pedestrians, cyclists, car drivers and bus passengers

Carried out by researchers at the University of Surrey’s Global Centre for Clean Air Research (GCARE) in partnership with North Carolina State University (NCSU) the study was conducted in Guildford, Surrey, during peak commuting hours in the morning and evening, and during off-peak hours in the afternoon.

Results from the study have suggested that cyclists and pedestrians were more likely to be affect by air pollution than those travelling by bus or car. Previous studies have suggested that car drivers may face the most exposure to air pollution during daily travel. In 2015, a study led by the University of Surrey suggested that drivers were particularly at risk of harm from particulates when stopping and starting at traffic lights (see story).

However, during the latest study, researchers used respiratory deposition doses (RDD) – a method that predicts the amount of pollutant particles left in someone’s respiratory system – to measure the impact on each of the four groups.

According to the study, the incidence of finer particles was 20% higher in pedestrians and cyclists than bus passengers, and 2.5 times higher than car drivers if they had windows closed and air conditioning systems on.


Commenting on the results Professor Prashant Kumar, director of the GCARE at 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 is 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. Active travel (cycling, walking) benefits the health of people due to increased physical activity. However, increased physical activity also means increased inhalation rates and hence the intake of more polluted air.”

The Guildford study comes after similar research in London has highlighted how travel choices can affect commuters’ air pollution exposure (see story).


Prof 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.”

Co-investigator of the study, Professor Chris Frey from the North Carolina State University, added: “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 organizations and governments promote healthier living by including exposure prevention as a criteria for land zoning and the built environment.”

Responding to the research, Rachel White, senior policy and political advisor at the walking and cycling charity Sustrans, said: “Whilst the findings from the University of Surrey that pedestrians and people on bikes are twice as likely to keep dangerous particles in their lungs than car drivers are important, it is vital to remember that in this country the health benefits of being physically active by bike or on foot always outweigh any costs from exposure to air pollutants.

“As our Bike Life survey across seven major UK cities shows — 78% of people want more dedicated space for cycling even if that involves taking space away from other road vehicles. We need local authorities to act now to provide a mix of protected direct routes connected to quieter back streets with lower air pollution to achieve modal shift and realise real health benefits.”

Related Links
Dynamics of coarse and fine particles exposure in transport microenvironments


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