What is ionizing radiation?

Related cancers:
Lung, bone, bone marrow (leukemia), thyroid, breast, liver, skin

Definition:
Ionizing radiation is energy released from the disintegration of unstable atomic nuclei during radioactive decay. This type of radiation may originate from X radiation or the emission of various subatomic particles from both natural and artificial sources. Some substances decay at faster rates than others and are more or less stable than others.

Exposure routes:

Inhalation, ingestion, direct external exposure

Where found: Ionizing radiation is both naturally occurring and artificially produced. It is found in radon (55 percent) and in the earth. Non-natural sources include military weapons, nuclear reactors, and electronic products. Technologically enhanced naturally occurring radioactive materials (TENORMs) concentrate ionizing radiation in solid sludge, water treatment facilities, aluminum oxide reactions, fertilizers, coal ash, concrete aggregates, diagnostic medical procedures, cable insulation, security screening equipment, and equipment used to kill microorganisms in food.

At risk: Children, pregnant women, industry workers, medical personnel, military personnel, residents in high background radiation areas

Etiology and symptoms of associated cancers: Ionizing radiation, regardless of the source, damages deoxyribonucleic acid (DNA, the genetic material) inside cells. The damage can be chromosomal breaks, cell mutations, and actual cell transformation. The consequences of this damage range from immediate cell death to transformation into cells that become malignant over time. The ability of ionizing radiation to kill cells explains its use to treat many cancers. Cancer cells divide more rapidly and are more vulnerable to radiation. Thus, ionizing radiation has the ability, when the trajectory of the beam is focused on a tumor, to shrink tumors by killing cells.

Immediate symptoms of exposure vary according to the type of particle, the dose, the length of exposure, and the route of exposure. Radiation sickness, or acute radiation syndrome, results from immediate excessive high-dose exposure. Whole body penetration damages the cardiovascular and central nervous systems. The blood pressure will drop (hypotension), and the brain will swell. Nausea, vomiting, convulsions, and confusion will follow. Death is inevitable when exposure is greater than 3,000 rads.

History: In 1896 Henri Becquerel presented his discovery of radioactivity in Paris at the Academy of Sciences. During the 1900s scientists Marie and Pierre Curie, Dmitry Mendeleyev, and Wilhelm Conrad Röntgen defined the properties of ionizing radiation. Many of the scientists working with ionizing radiation died as a result of their exposures. In 1970 the Environmental Protection Agency (EPA) began regulating ionizing radiation.

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