Ionizing Radiation

Higher frequency ultraviolet radiation begins to have enough energy to break chemical bonds. X-ray and gamma ray radiation, which are at the upper end of magnetic radiation have very high frequency --in the range of 100 billion billion Hertz--and very short wavelengths--1 million millionth of a meter. Radiation in this range has extremely high energy. It has enough energy to strip off electrons or, in the case of very high-energy radiation, break up the nucleus of atoms.

Ionization is the process in which a charged portion of a molecule (usually an electron) is given enough energy to break away from the atom. This process results in the formation of two charged particles or ions: the molecule with a net positive charge, and the free electron with a negative charge.

Each ionization releases approximately 33 electron volts (eV) of energy. Material surrounding the atom absorbs the energy. Compared to other types of radiation that may be absorbed, ionizing radiation deposits a large amount of energy into a small area. In fact, the 33 eV from one ionization is more than enough energy to disrupt the chemical bond between two carbon atoms. All ionizing radiation is capable, directly or indirectly, of removing electrons from most molecules.

Health Effects

The health effects of alpha particles depend heavily upon how exposure takes place. External exposure (external to the body) is of far less concern than internal exposure, because alpha particles lack the energy to penetrate the outer dead layer of skin.

However, if alpha emitters have been inhaled, ingested (swallowed), or absorbed into the blood stream, sensitive living tissue can be exposed to alpha radiation. The resulting biological damage increases the risk of cancer; in particular, alpha radiation is known to cause lung cancer in humans when alpha emitters are inhaled.

The greatest exposures to alpha radiation for average citizens comes from the inhalation of radon and its decay products, several of which also emit potent alpha radiation.

Protecting from external exposure to alpha radiation is easy, since alpha particles are unable to penetrate the outer dead layers of skin or clothing. However, tissue that is not protected by the outer layer of dead cells, such as eyes or open wounds, must be carefully protected.

The exposure pathways of concern are inhalation or ingestion of alpha emitters, which continue to emit alpha particles. Alpha emitting radionuclide's taken into the body release alpha particles directly to sensitive living tissues. As their high energy transfers directly to tissue, it causes damage that may lead to cancer.

The most significant way people come in contact with alpha emitters is in their home, school, or place of business. Radon, is a heavy gas and tends to collect in low-lying areas such as basements. Testing for radon in your home and taking any corrective action necessary is the most effective way to protect you and your family from alpha emitters.