Radium 226 was used in radioluminescent paint until the 1970's. Ra-226 is an alpha emitter. As StainesFS rightly points out, a sheet of bog roll can stop alpha radiation.
An issue with Ra-226 in cockpits is that, although alpha radiation is stopped by pretty much everything, older paint formulations tend to flake and become dusty. If the dust is breathed in, then you have energetic alpha particles in direct contact with the lungs, with the associated genetic damage.
Illuminated dials are behind glass, so they're pretty safe for everyone except dial restorers. The threat is from unprotected paint on surfaces such as switches.
The half life of Ra-226 is around 1600 years. On consumer products, for a time Ra-228 was added, a beta-emitter with a half-life of under 6 years. It made dials look much brighter for their first 5 years of life.
But for big bits of tin flying through radioactive clouds, as already stated the solution is simply to hose the things down. Hosed down a couple of buildings last year for exactly that reason.
The US used Sr-90 in paint for deck markers for a while. Sr acts like Ca, so binds with bones. Of course, as with pretty much everything else, the biological half-life (the time any particular atom remains part of a human body) is around 70 days, so a single exposure is unlikely to do any harm.
Last edited by Bushfiva; 21st Dec 2012 at 02:18.
Reason: Removed pointlessly aggressive phrase