ABSTRACT
Ionizing radiation occurs naturally from decay of radioactive materials or by the operation of x-ray emitting devices. A radioactive element spontaneously changes to a lower energy state and emits particles and gamma rays from its nucleus. X-rays result when highly energized electrons strike the nuclei of a targeted material. The electrons deflected from their path release energy as electromagnetic radiation or x-rays. Ionizing radiation occurs anytime an electron dislodges from its parent atom or molecule. Ionizing radiation’s ability to penetrate the body depends on wavelength, frequency, and energy of the material. Alpha particles do not penetrate the skin. An alpha particle cannot penetrate a thin layer of paper or clothing. Highly energized beta particles require shielding of some type of low-density material such as plastic, wood, water, or acrylic glass. Beta particles can travel a few centimeters into living tissue. Beta contaminants that remain on the skin for a prolonged period can cause injury. Beta emitting contaminants can also cause harm if deposited internally. Gamma and x-rays can penetrate human tissue. Radioactive materials that emit gamma radiation constitute both an external and internal hazard to humans. Gamma radiation frequently accompanies the emission of alpha and beta radiation. X-rays also possess longer wavelengths, lower frequencies, and lower energies than alpha or beta particles. The international community measures radiation using the System International (SI). The United States uses a conventional system of measurement depending on what aspect of radiation requires measurement (Table 14.1).
