Tube cars cause severe air pollution in the London Underground; oar wheels have been found to produce particularly small metal particles. This was revealed by a study conducted by scientists at the Center for Risk Studies of the University of Cambridge. The researchers note that these iron oxide particles are often much smaller than a single red blood cell.
According to the researchers, the pollution can thus be easily inhaled and end up entering the blood of the five million passengers who inhabit it borrow every day the London Underground. Previous research has linked this type of exposure to a higher risk of serious problems like Alzheimer’s disease and bacterial infections.
Maghemite
A similar phenomenon should also be observed in other underground systems in other parts of the world. However, the London Underground is particularly poorly ventilated.
“Scraps are by-products of the repeated operation of train brake pads, anti-slip pads and motor brushes,” said Hassan Sheikh, research lead and risk specialist at the University of Cambridge.
“They can also be released by the friction caused by the interaction between the metal wheels of the system’s wagons and the steel rails. The end result of this process is maghemite, a magnetic mineral released by friction and thrown by the continuous passage of successive rail cars through the subway system. »
Previous studies had already shown that overall levels of air pollution in the London Underground exceeded the limits set by the World Health Organisation. These studies also revealed the presence of particles resulting from the interaction of wheels, tracks and brakes.
Samples were taken from the platforms, ticket offices and cockpits of trains on the main lines of the London Underground, and maghemite was present in abundance throughout the underground system.
Experts warn that the problem is not limited to the London Underground. A study by the U.S. National Institute of Environmental Health Sciences also identified poor air quality, especially inhalable particles, as a looming problem for U.S. public transit, which hosts tens of millions of commuters every day .
Solutions at your fingertips
Aaron Bernstein, director of the Center for Climate Health and the Global Environment at Harvard University in Boston, also acknowledges the problem, but says he wouldn’t advise travelers to avoid the subway.
“In fact, subways in large cities manage to significantly reduce road traffic and associated air pollution,” adds Bernstein. “Also, they often have shorter travel times than their surface counterparts. Studies show that air quality needs to be considered in subways. It’s also perfectly possible. »
In this regard, Hassan Sheikh sees solutions in the use of magnets. “These can be used to attract and hold floating particles of iron filings, preventing them from wandering into subway systems,” says Sheikh.
“At this stage there are conflicting indications on the harmfulness of this particular type of pollution, compared to the exhaust fumes of urban traffic on the surface and in the open air,” Sheikh points out.
“More research is needed to provide more insight into these risks. In the meantime, however, the use of the mask by commuters could reduce direct exposure to iron oxide present in the subway. »
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