Cobalt

⁶⁰Co (with a half-life of 5.27 years) is used to irradiate food sources as a method of preserving food (Fig. IUPAC.27.1). The gamma radiation from ⁶⁰Co kills bacteria and other organisms that cause disease and spoilage of food (see Fig. IUPAC.27.1). The use of radioactive compounds for preserving food is not always viewed positively. Some individuals are concerned that harmful compounds will be produced during the irradiation process. However, there is no evidence to support the claim that irradiation is dangerous for food preservation [108]. Many medical products today are sterilized using gamma rays from a ⁶⁰Co source. This technique of sterilization is generally much cheaper and more effective than steam-heat sterilization because it is a cold process. For example, it can be performed on packaged items, such as disposable syringes. This sterilization technique is applicable to a wide range of heat-sensitive items, such as powders, ointments, and solutions, as well as biological preparations, such as bone, nerve, skin, etc., used in tissue grafts [108]. ⁶⁰Co is also used in industrial radiography to detect structural flaws in metal parts. The radiation can penetrate metals and the X-ray pattern produced by the radiating material can provide information on its strength, composition, and other properties [108]. Because of the above property, ⁶⁰Co is also used in leveling devices and thickness gauges used to test welds and castings [108].

⁶⁰Co is a radioactive metal isotope that is used in cancer treatments by radiotherapy. When ⁶⁰Co undergoes radioactive decay, high-energy gamma rays (energies of 1.17 MeV and 1.33 MeV) are emitted and have been used in brachytherapy to treat various types of cancer. Brachytherapy (brachy is Greek meaning “short distance”) is a method of radiation treatment in which sealed sources are used to deliver a radiation dose at a distance of up to a few centimeters by surface, intracavitary (insertion of the radioactive isotope in a body cavity), or interstitial (between cells) application [75]. ⁶⁰Co is used as a source of high-energy ionizing gamma radiation that can be directed to cancer cells from a device outside the body (external radiotherapy). ⁶⁰Co (and sometimes ⁵⁷Co and ⁵⁸Co, with half-lives of 0.75 year and 71 days, respectively) is the key component of the Schilling test, which is a method for determining whether a patient’s body is making and using vitamin B₁₂ properly. The cobalt isotope is used to label cobalt in vitamin B₁₂ to monitor how the body processes this essential vitamin [224]. ⁵⁷Co delivers the smallest radiation dose of all the cobalt isotopes. As a result, it has been used in the past for imaging and estimating organ size and location and in evaluating tumors of the head and neck [75], [99], [225], [226], [227].