Research: in-vehicle exposure to traffic and road-generated air pollution

We spend around 6% of our time commuting, but this can account for about 30% of our exposure to some air pollutants. There is widespread scientific consensus that short- and long-term exposures to air pollution are associated with significant health burdens for the population. This evidence continues to strengthen and evolve as air pollution is associated with a broader range of adverse health outcomes across the life course.

One area of key focus has been emissions from road transport and its impact on the health of vulnerable urban populations. The major focus has been on tailpipe emissions, mainly from diesel vehicles. Still, as combustion-powered vehicles are phased out as the UK transitions toward its environmental and net zero targets, greater emphasis is placed on understanding potential health impacts associated with non-exhaust emissions from motor vehicles – tire and brake wear and the resuspension of road dust.

Traffic-related air pollution

Collectively, these traffic-derived contributions, both pollutant gases and particles, comprise what is referred to as traffic-related air pollution, or TRAP. A new report by Imperial College London summarizes the evidence that TRAP impacts health. Still, it emphasizes the groups often excluded from discussions of potential exposures, health impacts, and mitigation – the more comprehensive road users, including drivers.

As TRAP concentrations fall off rapidly from the center of the road, drivers, bus passengers, and cyclists are technically at the most risk concerning exposure and are thus the groups who will most immediately benefit from actions to reduce vehicle pollutant emissions.

This report provides evidence on the exposures across these groups, and for cyclists and pedestrians, contextualizes exposure against the health benefits associated with increased physical exercise.

Key findings

This is an emerging area, and the evidence base is not always complete or entirely consistent, but overall, several key messages emerge:

  • Drivers’ exposure to TRAP in traffic is often underestimated, and this is mainly an issue for individuals for whom driving is a significant component of their work. Car drivers in London are likely to be among the biggest beneficiaries of moves to penalize highly polluting vehicles in London.
  • Active transport modes remain beneficial even with high exposure doses, but better segregation from highly polluted road environments would be further helpful. All road users benefit from actions that reduce vehicle emissions.
  • With an eye to the future, more consideration will have to shift to tire and brake wear contributions, for which technological mitigation measures already exist or are in development.

While the extent of exposure depends on the car, the air-tightness of the cabin, any filters installed, and how the vehicle is used, drivers (taxi drivers are worst affected) can experience more of some of the most damaging forms of pollution than cyclists, bus passengers, or pedestrians, according to the report from Imperial College London.

The Imperial College researchers looked at findings from around the world on the exposure to air pollution from traffic among different types of road users. They found that cyclists were exposed to about 20% less PM2.5 pollution than car users, and pedestrians were exposed to about 40% less.

Source: Mayor of London

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