Radioisotope Cesium-137 (Cs-137)

Chemical properties
Cesium is a silvery white, soft, ductile metal with only one oxidation state (+1). It exists as liquid at room temperature, but readily bonds with chlorides to form a powder.

Mode of decay
Beta and gamma radiation

Half-life
30.17 years

Uses of Cesium-137
Cs-137 is used in small amounts for calibration of radiation-detection equipment, such as Geiger-Mueller counters. In larger amounts, Cs-137 is used in medical radiation therapy devices for treating cancer; in industrial gauges that detect the flow of liquid through pipes; and in other industrial devices to measure the thickness of materials, such as paper, photographic film, or sheets of metal.

Sources of Cesium-137
Cs-137 is produced by nuclear fission for use in medical devices and gauges. Cs-137 also is one of the byproducts of nuclear fission processes in nuclear reactors and nuclear weapons testing.

Exposure to Cesium-137
1. Nuclear reactor waste and accidental releases such as the Chernobyl accident in the Ukraine release some Cs-137 to the environment. Spent nuclear fuel reprocessing plant wastes may introduce small amounts to the environment.
2. Cs-137 found in radiation therapy units in hospitals and industrial gauges. The sources in these devices are designed to remain sealed and keep people from being exposed; however, if these canisters are intentionally or accidentally opened, the Cs-137 inside could be dispersed.
3. Walking on Cs-137 contaminated soil could result in external exposure to gamma radiation. Leaving the contaminated area would prevent additional exposure.
4. Coming in contact with waste materials at contaminated sites could also result in external exposure to gamma radiation.
5. If Cs-137 contaminated soil becomes air-borne as dust, breathing the dust would result in internal exposure. Because the radiation emitting material is then in the body, leaving the site would not end the exposure.
6. Drinking Cs-137 contaminated water, would also place the Cs-137 inside the body, where it would expose living tissue to gamma and beta radiation.

Health effects of Cesium-137
External exposure to large amounts of Cs-137 can cause burns, acute radiation sickness and even death. Exposure to Cs-137 can increase the risk for cancer because of exposure to high-energy gamma radiation. Internal exposure to Cs-137, through ingestion or inhalation, allows the radioactive material to be distributed in the soft tissues, especially muscle tissue, exposing these tissues to the beta particles and gamma radiation and increasing cancer risk.

Source: Centers for Disease Control and Emergency, U.S. Environmental Protection Agency