Ionizing Radiation

Radiation can generally be defined as being ionizing or non-ionizing. Ionizing radiation consists of high-energy waves that are able to penetrate cells and can cause ionization in different parts of the cell. Ionization is the development of a positive charge in a molecule (group of atoms) that is normally neutral (without a charge). Ionized molecules are unstable and quickly undergo chemical changes. This can lead to the formation of free radicals that can damage the molecule or other molecules around it.

One type of molecule that is sensitive to ionizing radiation is DNA, the part of the cell that contains the genes (blueprints) for each person's characteristics. Ionizing radiation can lead to a mutation (change) in a cell's DNA, which could contribute to cancer, or to the death of the cell. All cells in the body can be damaged by ionizing radiation. The amount of damage is related to the dose of radiation received by the cell. While the process of cellular change from radiation takes only a fraction of a second, other changes such as the beginning of cancer may take years to develop.

Types of ionizing radiation include x-rays, gamma rays, cosmic rays, and particles given off by radioactive materials such as alpha particles, beta rays, and protons. These forms of radiation have different energy levels and can penetrate cells to different extents, but all are capable of causing ionization.

People may be exposed to 3 main types of ionizing radiation:

* Natural background radiation comes from cosmic rays from our solar system and radioactive elements normally present in the soil. This is the major contributor to worldwide radiation exposure.

* Non-medical synthetic radiation occurs as a result of above ground nuclear weapons testing that took place before 1962 as well as occupational and commercial sources.

* Medical radiation comes in the form of diagnostic x-rays and other tests, as well as from radiation therapy. Radiation therapy is currently used to treat some types of cancer and involves dosages many thousand times higher than those used in diagnostic x-rays.