Once went on a day-trip with some friends to London, by coach.
We didn't do anything unusual or go anywhere obviously grubby, but I was shocked when I washed my hands later at the colour of the water running off them.
They were nearly as bad as as after a day at the club track. In fact steam-oil and coal dust would have been more hygienic in the pathogen stakes, though eating one's snap with engineering grime on your mitts is not best practice either.
The culprit? No more than lots of door-fittings, handrails and such like in public buildings and The Underground, plus airborne dust.
'
That trip, and those track experiences, would have been about half a century ago now, and I seem to be still here.
I should add the club now has not only a far better track, but also the proper facilities, "downstairs cloakroom" and all, it had lacked for decades!