Radiation and the Effects on the Human Body 

Mr. Wizard !!!!!

Alpha - Large particles so it has a hard time piercing the thinest material (including skin). Little to no danger

Beta - A forth the of the size of alpha particles, so it has a much better rate of penetration. As you can see in the video 1/2 inch of plywood was sufficient to block almost all of the particles. Could do major damage (depending on the concentration and duration of exposer) to the epidermis but internal organs are still fairly safe

Gamma- Photon (light radiation) little to no problem piercing the human body.  In addition carries a large amount of energy in a very small package.  Can be very, very dangerous.

I would certainly not handle a source with my bare hands

  So examining the dangers of radiation, the larger the particle the least dangerous it is.  The alpha particle is of little concern to us it can't even penetrate a signal piece a paper, not to mention layers and layer of skin.  

   Beta on the other hand is far more dangerous as some level of penetration ability.  Beta particles also have a great deal of energy compared to the larger alpha particle

Gamma is the most dangerous type of radiation, with both very high energy and strong penetration, gamma radiation has the capability to penetrate most of the internal organs on the human body.  Protective clothing only provides a limited protection and only true method of avoiding radiation sickness or death is to limit the length of exposure. 

The Not So Hidden effect of radiation