A radiological hazard is defined as an unintentional exposure to materials that emit ionizing radiation. The primary radiological hazard is the health effects resulting from unintentional exposure to ionizing radiation. When radiation interacts with atoms, energy is deposited, resulting in ionization (electron excitation). This ionization may damage certain critical molecules or structures in a cell.

Ionizing radiation is emitted from molecular elements generally referred to as radio nuclides, and this radiation has the ability to alter in varying amounts the function of living processes at the cellular level. Types of ionizing radiation include Alpha particles, Beta particles, Gamma rays, X-rays, and Neutron particles.

Measuring Radiation
Radiation is measured in different ways. Measurements used in the United States include Roentgen, radiation absorbed dose (RAD), and roentgen equivalent man (REM). The term RAD is being replaced by the International System skin dose unit for radiation absorbed dose, the gray (Gy) which is a measurement of absorbed dose in any material. 1 Gy equals 100 RAD.

The nature and extent of damage caused by ionizing radiation depend on a number of factors including the amount of exposure (energy strength), the frequency and/or duration of exposure, and the penetrating power of the radiation to which an individual is exposed. Acute exposure to very high doses of ionizing radiation is rare but can cause death within a few days or months. The sensitivity of the exposed cells also influences the extent of damage. For example, rapidly growing tissues, such as developing embryos, are particularly vulnerable to harm from ionizing radiation.

Types of Radiation
Radiation effects fall into 2 broad categories:
  • Direct effect on cells (direct impact with a particularly sensitive atom or molecule in a cell)
  • Indirect effect on cells (interaction with water molecules in the body where the deposited energy in the water leads to the creation of unstable, toxic hyperoxide molecules which then damage sensitive molecules and afflict subcellular structures)
Nuclear power plants are a significant potential source of ionizing radiation. The health and environment impacts from the Three-Mile Island and Chernobyl, Russia disasters illustrate the potential hazards from nuclear power plants. Other sources of ionizing radiation include medical and diagnostic X-ray machines, certain surveying instruments, some imaging systems used to check pipelines, radioactive sources used to calibrate radiation detection instruments, and even some household fire detectors.