Commuters who use public transport are exposed to up to eight times the level of pollutants as motorists, a study has found.
Researchers discovered that passengers are exposed to cancer-causing particulates, which come from dust in the air and vehicle fumes, when windows are kept open on buses and trains for ventilation. Those in cars are insulated from this by closed windows and air conditioning systems.
The report, by scientists at the University of Surrey, found those who travelled on the London Underground experienced the worst quality air levels. This is because trains on deep lines kick up harmful dust, which becomes concentrated in the air, and use open windows for ventilation.
After the Tube the next highest level of exposure to pollutants came on buses, due to the length of journey and similar reliance on open windows for ventilation.
While those who drove diesel cars into work were typically exposed to the least pollution, the study found that per person they added six times the amount of particulate matter to the environment compared with those who take the bus.
The study also found that because those from areas of greater affluence were more likely to have access to a car, they would in turn experience less pollution to those living in more deprived areas who relied predominantly on the bus or other forms of public transport to get to work.
Poor air quality is estimated to cost Britain’s economy £3.7billion a year, and contributes to 9,400 deaths annually in London alone.
Academics assessed air pollution levels on typical commuting routes, checking hundreds of journeys by commuters using buses, cars and Tube.
Because bus journeys were 17-42 minutes longer than car journeys, it meant that bus passengers were exposed to higher levels of pollution for longer periods of time.
As such, the levels of PM that commuters using the bus were exposed to were up to five times higher than those who travelled in the car.
Dr Prashant Kumar, of the University of Surrey, who led the study, said: ‘There is an interesting trade-off of pollution exposure between different modes of transport.
‘For example, commuters travelling to work on Underground trains are exposed to the highest levels of large-sized particles while being exposed to the highest level of black carbon and ultrafine particles during commute in buses.
‘The relatively new airtight trains with closed windows showed a significant difference to the levels of particles people are exposed to over time, suggesting that operators should consider this aspect during any upgrade of Underground trains, along with the ways to improve ventilation in underground tunnels.’
‘We found that there is definitely an element of environmental injustice among those commuting in London, with those who create the most pollution having the least exposure to it.’
Typically, those who travelled into work by car left their windows up and so the driving cabin was sealed from outside pollutants. Those who used the bus, while exposed to pollutants through the open windows, also experienced the pollution at each bus stop when doors opened to allow passengers off.
The study comes as Sadiq Khan, the Mayor of London, is to introduce a £10 daily charge on any pre-2005 diesel car driving in central London, while encouraging diesel drivers to buy cleaner alternatives with calls for a national scrappage scheme.