London’s air quality is an unmitigated disaster: It took just five days for the U.K. capital to surpass its pollution limit for 2017, and the city’s smog kills around 10,000 residents each year. Drivers are some of the principal culprits, causing most of the city’s pollution, but a new study from the University of Surrey found that they suffer almost none of their own consequences. Ironically, it’s the city’s Tube passengers who breathe in the most pollution, despite trying to do the environmentally friendly thing by taking public transportation.
Tube passengers were exposed to an average of 68mg of particulate matter on their commutes, whereas car passengers breathed in only 8.2 mg. Bus passengers, exposed to 37mg, fell in the middle. The discrepancy comes down to windows: Cars usually travel with windows closed, with the air coming in through efficient filtering systems. Passengers on the bus and Tube, on the other hand, often ride with their windows open. Tube cars get stuffy at the best of times, and in the summer, unairconditioned buses and rail cars are insufferable without a gust of “fresh” air.
While its indisputable that Tube passengers are the worst off when it comes to inhaling pollution, there’s a twist: Not all Tube lines are equal, because not all Tube cars have opening windows. Researchers found that trains with open windows leave their passengers far more exposed to PM than those with closed windows. The District line, for example, has trains with cars that have both sealed and opening windows. Passengers in open cars got more than double the dose of particulate matter than those in closed cars.
And there’s the fact that the Tube–or the London Underground, to use its official title–isn’t all underground. Many stations and lines are outside, and these also saw less PM than the network’s tunnels and underground stations, which trap the pollution created by the cars lurching blissfully unaware through the city’s streets above.
When the University of Surrey researchers embarked on the study, they intended to look at the difference in pollution exposure for various socioeconomic groups. They found that there is indeed a difference, but only because of the breakdown of transport type. Richer people tend to favor cars, whereas poorer people take the bus. London has good Tube coverage, but the further you get from the center, the more you have to rely on buses to get around.
But this doesn’t tell the whole story. Many high-paid city traders, for example, commute to work on the Tube, because–despite its overcrowding and iffy reliability–it’s the fastest and most convenient way to get around London. Consequently, the socioeconomic lines the researchers believed they would discover are not so clear-cut. The true injustice is perhaps put best by the lead researcher, Prashant Kumar, who told the University of Surrey media center: “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.”
The problem remains, as in every city, with cars, trucks, and delivery vehicles. Cities like London, which already have a comprehensive public transit system, have a built-in advantage when it comes to getting commuters off the roads. But when the alternative is to breathe air that is six times filthier than what you’d get in your comfy (albeit traffic-jammed) car, then it’s tougher to convince people to give up their private transport.
All the more reason, then, for cities to work on the “stick” part of the proverbial carrot-and-stick equation, and make it as difficult and unpleasant as possible to use a car. Getting vehicles off the road is the only clear-cut way to clean up the air–and freeing up the air at the street level will also clean it up down in the tunnels.