They are effectively shielded by thin layers of metal or plastic and are again only considered hazardous if a beta emitter is ingested or inhaled. Gamma emitters are associated with alpha, beta, and positron decay. X-Rays are produced either when electrons change orbits within an atom, or electrons from an external source are deflected around the nucleus of an atom. Both are forms of high energy electromagnetic radiation which interact lightly with matter. X-rays and gamma rays are best shielded by thick layers of lead or other dense material and are hazardous to people when they are external to the body.
Neutrons are neutral particles with approximately the same mass as a proton.
Because they are neutral they react only weakly with material. They are an external hazard best shielded by thick layers of concrete. Neutron radiation will be discussed in more detail in the discussion of nuclear power.