A hot particle is a microscopic piece of radioactive material that can become lodged in living tissue and deliver a concentrated dose of radiation to a small area. A controversial theory proposes that hot particles within the body are vastly more dangerous than external emitters delivering the same dose of radiation in a diffused manner. Other researchers claim that there is little or no difference in risk between internal and external emitters.

The theory has gained most prominence in debates over the health effects of nuclear accidents, dirty bombs or fallout from atomic weapons, all of which can spread hot particles through the environment. The current ICRP risk model for radiation exposure is derived from studies of victims of external radiation, and detractors claim it does not adequately estimate the risk of hot particles.

 

Note:   The above text is excerpted from the Wikipedia article Hot particle, which has been released under the GNU Free Documentation License.