 When we are near a source of radiation, such as radioactive material, we can be exposed to the radiation emitted without becoming contaminated by the source. One way to think about exposure is to consider x-rays. When you have a chest x-ray, for example, you are exposed to radiation, but you don't become contaminated with radioactive material. We can reduce our exposure to radiation if we are shielded in some way. For example, by standing behind a concrete wall or keeping the radioactive source inside of a lead container. To become contaminated, radioactive material must get on the skin or clothing or inside of the body. For example, consider a dirty bomb that is a conventional explosive such as dynamite that is laced with radioactive material. When the device is detonated, people could not only be injured by the blast, but become contaminated. External contamination refers to radioactive material on the outside of the body. When a person becomes externally contaminated, simply removing the clothing can remove as much as 90% of the contamination. Gently washing the skin and the hair can remove most of that which remains. If a person ingests or inhales radioactive material, it can become incorporated in the organs of the body, and this is called internal contamination. Depending on the type of radioactive material which someone is contaminated with, certain medications can be administered to accelerate the rate at which the material is eliminated from the body. Examples of such medications include Prussian Blue and DTPA.