New Leicester research has found that people who commute by car can be subject to higher levels of harmful gases than those who walk or cycle to work.

The study, conducted by researchers at the University of Leicester in partnership with Leicester City Council, is published in the Journal of Transport & Health.

Experts found that in-cabin levels of nitrogen dioxide (NO₂) — a key indicator of air quality and harmful when breathed in by humans — were higher for weekday morning commuters travelling by car, compared to their counterparts travelling by bike or on foot. However, the concentration of fine particulate matter (PM_2.5) was shown to be slightly lower for drivers.

Researchers studied four typical routes used by Leicester commuters between city suburbs and the city centre, and used air quality sensors in volunteer walkers’ and cyclists’ backpacks to measure the concentrations of NO₂ and PM_2.5. The same devices were also fitted in the cabin of a Nissan Leaf electric vehicle. An electric car was used in order to determine driver exposure to pollutants without interference from the car’s own exhaust.

Their findings show that NO₂ concentrations can be higher in car cabins (even electric car cabins) than alongside the road where people are walking and cycling. Some PM_2.5 can be removed, for example by pollen filters, meaning PM_2.5 might be slightly lower in car cabins than alongside the road, but NO₂ can be drawn directly into the cabin from the exhaust of traffic in front. This will change as more electric cars come into use, but provides evidence to support the benefits of getting out of a car and walking or cycling instead.

Dr Rikesh Panchal is a Research Associate within the University of Leicester’s Centre for Environmental Health and Sustainability, and lead author for the study. He said:

“Anecdotal evidence on public perceptions of air quality during commuting collected by Leicester City Council suggested that people believed that exposure to harmful pollutants was higher for active commuters than for car occupants.

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