The researchers recruited 140 professional drivers from a range of occupations working in central London. The drivers were asked to carry black carbon monitors, which were linked with GPS trackers, for 96 hours. The monitors measured exposure levels once every minute. Drivers were also asked about the type of vehicle they drive, their working hours and whether they drive with their windows or air vents open.
The results showed that, on average, professional drivers were exposed to 4.1 micrograms of black carbon per cubic metre of air (μg/m3) while driving, which was around four times higher than their exposure at home (1.1 μg/m3). Researchers say the levels recorded at home are similar to levels experienced by office workers at their desks. Professional drivers also experienced extremely high spikes in exposure to black carbon, often exceeding 100 μg/m3 and lasting as long as half an hour.
During the same period, researchers found that pollution levels at a busy London roadside (Marylebone Road) were 3.1 μg/m3 on average and, away from the roadside, the average level in London was 0.9 μg/m3.
We don't know for sure why taxi drivers fare the worst, but it might be because taxis tend to operate in the busiest and most polluted parts of the city where 'street canyons' restrict the movement of air
Taxi drivers had the highest levels of exposure on average (6.5μg/m3). Emergency services workers had the lowest levels of exposure on average (2.8 μg/m3).
The research, carried out in collaboration with researchers from Queen Mary University of London, was previewed at the European Respiratory Society International Congress on 29 September 2019. The full research findings with guidance and resources will be published in early 2020.
Lead researcher and King's PhD candidate Shanon Lim said: "We know quite a lot about the dangers of exposure to traffic pollution. However, there has been surprisingly little research on levels of professional drivers' exposure to pollution and its effects on their health. We believe there are around a million people working in jobs like these in the UK alone, so this is a widespread and under-appreciated issue.
"We don't know for sure why taxi drivers fare the worst," he added, "but it might be because taxis tend to operate in the busiest and most polluted parts of the city where 'street canyons' restrict the movement of air."
The next steps in this research include investigating possible strategies for protecting drivers, such as the use of air filters. Lim said: "This is vital to help employers, occupational safety and health professionals and individual workers reduce exposure and minimise work-related health risks."
