When a London Underground train hits the brakes, its wheels grind against the tracks, throwing up tiny specks of metal and other particles. There’s concern that this ‘Tube dust,’ could be damaging the health of passengers and workers on the network.
Yesterday, the London Assembly’s environment committee met to discuss the issue, which first started gaining attention in the 1990s, but has been given new impetus by Sadiq Khan’s efforts to clean up the city’s air since taking over as Mayor in 2016.
Airborne particles are ranked according to their size, with those under 2.5 microns (classed as PM2.5) generally considered the most potentially damaging to health because they’re small enough to get deep into the lungs, and then into the bloodstream and internal organs. The levels of PM2.5 particles on the Tube are between 30 and 40 times higher than above ground, but that doesn’t necessarily mean it’s more dangerous.
Above ground, especially in London, the air is full of known carcinogens, nitrogen dioxide and carbon monoxide from exhaust fumes, which aren’t present below the surface. Down there, it’s more likely to be iron oxide – which may or may not be harmful.