If you regularly ride the tube, it won't surprise you to find out the entire thing is filthy. But what might interest you is that there's a pretty big difference in how dirty different tube lines are.
New research from Dr Ed has revealed the most bacteria ridden tube lines and stations, with the Northern Line taking the filthy crown.
The survey involved swabbing 60 surfaces in 10 busiest tube lines and stations and tested the samples bacteria levels for colony-forming units (CFU), which means the number of viable bacteria cells that thrive in every 10 centimetres.
Sadly if you have to brave the Northern Line to work, it has nearly three times the number of germs as the Central Line, which comes in a number two, followed by the Bakerloo Line, Waterloo and City Line, the DLR, the Victoria Line and the Jubilee Line.
And the cleanest you ask? The Hammersmith and City Line by a long way.
Infographics from Dr Ed also reveal some uncomfortable truths about places which are cleaner than the filthy tube. Your toilet, for one.