Radiation injury is damage to tissues caused by exposure to ionizing radiation.
Large doses of ionizing radiation can cause acute illness by reducing the production of blood cells and damaging the digestive tract.
A very large dose of ionizing radiation can also damage the heart and blood vessels (cardiovascular system), brain, and skin.
Radiation injury due to large and very large doses is referred to as a tissue reaction. The dose needed to cause visible tissue injury varies with tissue type.
Ionizing radiation can increase the risk of cancer.
Radiation exposure of sperm and egg cells carries little increased risk of genetic defects in offspring.
Doctors remove as much external and internal (that which is inhaled or ingested) radioactive material as possible and treat symptoms and complications of radiation injury.
In general, ionizing radiation refers to high-energy electromagnetic waves (x-rays and gamma rays) and particles (alpha particles, beta particles, and neutrons) that are capable of stripping electrons from atoms (ionization). Ionization changes the chemistry of affected atoms and any molecules containing those atoms. By changing molecules in the highly ordered environment of the cell, ionizing radiation can disrupt and damage cells. Depending on the magnitude of the dose, organs exposed, and types of radiation cellular damage caused by ionizing radiation can cause acute illness, increase the risk of developing cancer, or both.
Ionizing radiation is emitted by radioactive substances (radionuclides), such as uranium, radon, and plutonium. It is also produced by devices, such as x-ray and radiation therapy machines.
Radiation Sickness
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Radio waves, such as from cell phones and AM and FM radio transmitters, and visible light also are forms of electromagnetic radiation. However, because of their lower energy, these forms of radiation are not ionizing, and thus public exposure to these common sources does not damage cells. In this discussion, “radiation” refers exclusively to ionizing radiation.
Measurement of radiation
The amount of radiation is measured in several different units. The roentgen (R) is a measure of the ionizing ability of radiation in air and is commonly used to express the intensity of exposure to radiation. How much radiation people are exposed to and how much is deposited in their body may be very different. The gray (Gy) and sievert (Sv) are measures of the dose of radiation, which is the amount of radiation deposited in matter, and are the units used to measure dose in humans after exposure to radiation. The Gy and Sv are similar, except the Sv takes into account the effectiveness of different types of radiation to cause damage and the sensitivity of different tissues in the body to radiation. Low dose levels are measured in milligrays (mGy, 1 mGy = 1/1000Gy) and millisieverts (mSv, 1 mSv = 1/1000Sv).
Contamination vs. irradiation
An individual''s radiation dose can be increased in two ways, contamination and irradiation. Many of the most significant radiation accidents have exposed people to both.
Contamination is contact with and retention of radioactive material, usually as a dust or liquid. External contamination is that on skin or clothing, from which some can fall or be rubbed off, contaminating other people and objects. Internal contamination is radioactive material deposited within the body, which it may enter by ingestion, inhalation, or through breaks in the skin. Once in the body, radioactive material may be transported to various sites, such as the bone marrow, where it continues to emit radiation, increasing the person''s radiation exposure, until it is removed or emits all its energy (decays). Internal contamination is more difficult to remove than external contamination.
Irradiation is exposure to radiation but not to radioactive material, that is, no contamination is involved. A common example is diagnostic x-rays, used, for example, to evaluate a broken bone. Radiation exposure can occur without direct contact between people and the source of radiation (such as radioactive material or an x-ray machine). When the source of the radiation is removed or turned off, irradiation ends. People who are irradiated but not contaminated are not radioactive, that is, they do not emit radiation, and their dose from that source of radiation does not continue to increase.
