How Bad Is the Air Quality on the London Underground?

If you’ve traveled around London on public transit during the summer, you know how sweaty and stuffy the experience can be. But the lack of air conditioning is only one of the hazards. A 2017 study by the University of Surrey found that particulate levels in the London Underground system can be as much as eight times higher than what a car driver experiences on the city’s roads. The Tube pollution comes from “mechanical abrasion between rails, wheels and brakes” in its poorly ventilated subterranean environment.

Open windows let pollution in:

• Brake wear from trains in any subway system churns out particulate emissions, but the design of the London Underground, with narrow tunnels and very limited air conditioning, may be making things worse.
• On the Northern and Victoria Lines, where windows can be opened, particulate levels run higher. Riders open windows in summer because the trains’ ventilation system moves so little air.
• The study found that Londoners traveling by bus are also exposed to high particulate levels -- not because buses create more emissions, but because open windows allow more polluted air inside.