I've always been lead to believe that carbon dust is very bad for one's health, but I think the residual smoke that seeps out of engines on turn arounds is probably just as bad. Jet fuel, turbine oil, hydraulic fliud, sealants, paints used in manufacture and repair are also nasty when contact is allowed.
I occasionally look up at the overhead and see a "high voltage inside " decal wondering how much electro magnetic radiation is being pumped out.
And I haven't even mentioned blue loo or worse- crew meals.