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Taxi drivers face highest level of black carbon exposure

Taxi drivers in London experience the highest exposures to black carbon compared to other professional drivers.

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New research has found that taxi drivers in London experience the highest exposures to black carbon compared to other professional drivers such as couriers, truck drivers, waste removal and emergency service workers. Black carbon is the sooty black material emitted predominantly from diesel engines in the urban environment.

In a recent study, researchers from King’s and Queen Mary University of London recruited 140 professional drivers from a range of different occupations working in the heart of London. The drivers were asked to carry black carbon monitors for 96 hours, which were linked with GPS trackers. 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 down or air vents open.

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.”

On average, the results showed that professional drivers were exposed to 4.1 micrograms of black carbon per cubic metre of air (µg/m3) while driving, around four times higher than their exposure at home or levels experienced in offices. During the same period, researchers found that pollution levels at Marylebone Road were 3.1 µg/m3 on average and, away from the roadside, the average level in London was 0.9 µg/m3.

“Our study suggests that professional drivers are exposed to high levels of traffic pollution while at work. Because these levels are higher than those we find at the roadside, this suggests that being inside a vehicle doesn’t necessarily offer any protection, in fact the opposite may be true: that air pollution can get trapped inside the vehicle for extended periods of time”, Mr Lim said.

From the study group of 140 drivers from different professions, taxi drivers had the highest levels of exposure on average (6.5 µg/m3). Emergency services workers had the lowest levels of exposure on average (2.8 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. On the other hand, emergency services can avoid congestion when they are attending an incident.– Shanon Lim, Department of Analytical, Environmental and Forensic Sciences

The results also showed that keeping car windows closed halved the levels of black carbon for professional drivers, while the type of vehicle and choice of route could also lower exposure.

Mike Hedges, a taxi driver for almost 30 years and a Masters student at King’s studying Global Air Pollution and Health said: “As a London taxi driver driving in the most polluted streets in London, I have always wanted to improve the air quality in London. I became involved in helping successive London Mayor's develop their air quality strategies for London's taxis and engaging with taxi drivers in helping them understand their own personal air pollution exposures through Unite, my trade union.

“Through research funded by the Institution of Occupational Safety and Health, I worked with taxi drivers to facilitate them carrying personal monitors to record their personal exposure, showing them the realities of the air, they are breathing every day."

Although the air pollution hasn't had any impact on my health, many of my colleagues have been affected and I think tackling London's air quality should be a priority to protect taxi drivers, who are the most exposed group of occupational drivers.– Mike Hedges, taxi driver and Masters student at King’s

Mr Hedges, who used to drive diesel taxis most of the time, switched to an electric taxi one and a half years ago.

Next steps in this research include investigating possible strategies for protecting drivers, such as the use of air filters. Mr Lim said: “This is vital to help employers, occupational safety and health professionals and individual workers reduce exposure and minimise work-related health risks.”