Black "dust" on the Underground

[OCdude]

As any one here who frequently uses the London Underground knows, there's a "lovely" fine black dust that seems to coat everything (and is extra lovely when you get home and blow you nose, only to discover you're actually carrying about 1lb of it up there!)

Anyway i'm slightly curious as to what the hell it actually is.... I guess it could just be 'normal dust' (i.e. dead skin etc... ew) plus brick dust from the tunnels and other bits... but i've also read that (apparently) it's actually fine metal grindings, from where the wheels grind away at the track!?

Anyway - anyone have any ideas?

 

[OCdude]

Snort it and tell us what happens.

I do, at least twice a day

 

[OCdude]

I work on the cctv, so I spend most my time replacing camera's the stuff ruins, its mainly brake dust, dead skin, that sort of thing, its not the nicest thing in the world to be covered in (ive seen people come out black head to toe after opening a panel on the platforms).

Bakerloo is the worst for it (I swear theres a bloody coal factory at each end!)

3 lines which I've narrowed down as being the worst, are:

#1 Victoria
#2 Bakerloo
#3 Central