Originally Posted by Scoop
tetanus of the lungs would be bad
Just thought I'd mention that tetanus, despite popular belief, is not a rust-related phenomenon. Tetanus is an anaerobic bacterium and is more likely to be found deep in soil and other environments deprived of oxygen. Anything that has managed to rust would prove quite inhospitable to the pesky germ since the very event of rusting depends on the presence of air.
So rust is merely oxidized iron. I imagine smoking with a rusted hookah would be completely safe, but if it imparts any flavor on the smoke... well, that'd be nasty. As for cleaning it, I'd suggest any of the rust cleaning products already mentioned to loosen the buildup followed by a stiff brush doped with an abrasive such as Brasso to get rid of the stubborn bits. Really, the best method would be to sand it off, but the nature of being a tube makes this kind of difficult. Perhaps a wooden dowel wrapped in sand paper? Of course, remember to clean well before use to remove these harsh chemicals completely and any debris.