The name “cesium” derives from the Latin word for “sky,” caelum. Cesium (Cs) is among the most rare and reactive alkali metals. Elemental cesium (Cs0) is silvery white, soft, and malleable. It has a relatively low melting point of 82.4°F (28°C) and thus exists as both solid and liquid at room temperature. Elemental cesium (Cs0) ignites violently when exposed to moist air or water but forms stable salt complexes. The greatest concentration of naturally occurring cesium (32%), the compound cesium oxide (Cs2O), is found in the ore pollucite.1,81,83 Since Cs0 is so highly reactive and short-lived, the name “cesium” will refer to cesium salts in the following discussion, unless specifically noted otherwise.
Radionuclides of cesium were identified in the 1940s by the American scientist and Nobel Prize winner Glenn Seaborg and his student Margaret Melhase.63 Radioactive cesium isotopes are products of nuclear fission of uranium and plutonium.85 Both 134Cs and 137Cs decay via β particle emission; however, 137Cs also emits γ rays.81 Because 137Cs has a long half-life of 30 years, it serves not only as an “atomic clock” but also poses potential radiological hazard as it deposits and complexes in earth and water. Of the numerous cesium radioisotopes that are identified to date, only 133Cs is stable.9
Several releases of radioactive cesium have occurred in the past century, resulting in large-scale contamination and human exposure. Examples include the nuclear weapons use in Hiroshima and Nagasaki; nuclear weapons testing in Bikini Atoll11 and Republic of Georgia;26 poor nuclear waste management in Goiânia,36,60,68 Tammiku,37 and Camp Lilo in the Republic of Georgia;26 as well as critical nuclear power plant malfunctions in Chernobyl71 and Fukushima Daiichi.42
Occupational exposure to radiocesium occurs routinely in nuclear power plant employees and people who live and work in close proximity to a nuclear facility. Both 137Cs and 131Cs are used as sources of external and internal radiation for treatment of numerous malignancies. Internal radiotherapy with 131Cs seed implantation, called brachytherapy, is approved by the US Food and Drug Administration (FDA).23 Physicians and staff working with these isotopes are at risk of occupational exposure.24,61
Cesium compounds are employed in scintillation counters, photoelectric cells, vacuum tubes, optical instruments, semiconductors and extensively in alternative medicine.1 They serve as catalysts for organic synthesis and are utilized for laboratory experiments in animal models of ventricular dysrhythmias. Nonradioactive cesium chloride is promoted as a supplement or an alternative treatment for cancer, despite no scientific support for this claim. Its increasing popularity in cancer treatment stems from a theory that cesium chloride increases the intracellular pH of tumor cells, resulting ...