Cobalt-60

Source: Neutron activation of stable Co-59; Half-Life: 5.3 years Effective Half-Life: 10 days Specific Activity: 1,100 Ci/g Decay Mode: Beta GI Absorption: 5-30% Lung Clearance Half-Time: >100 days for oxides, hydroxides, halides, and nitrates; 10-100 days for other compounds; Critical Organ: Total body Internal Toxicity: High Annual Limit on Intake: 0.030 mCi Tenth-Value Layer: 34.8 mm Pb Gamma Ray Constant: 13.2 R/h @ 1 cm per mCi Radiation Energy (MeV): Beta 0.313 (99.8%); Gamma 1.17 (99.8%); Gamma 1.33 (100%) Radiation Accidents: 31 accidents reported with 211 injuries and 30 deaths plus C0-60 was involved in 16 incidents of Melting of Radioactive Materials; [See Glossary for references.] See Radiation, ionizing.

Cobalt-60

Radioactive material

Atomic number: 27

Cobalt-60m

Radioactive material

Atomic number: 27

Exposure to high amount of cobalt can cause heart, lung, kidney, and liver damage. Skin contact is known to result in contact dermatitus. Cobalt may also have mutagenic and carcinogenic effects. Exposure to cobalt radiation causes cell damage and can lead to severe burns and death at high doses. (L29, L30)

Cobalt is believed to exhibit its toxicity through a oxidant-based and free radical-based processes. It produces oxygen radicals and may be oxidized to ionic cobalt, causing increased lipid peroxidation, DNA damage, and inducing certain enzymes that lead to cell apoptosis. Cobalt has also been shown to block inorganic calcium channels, possibly impairing neurotransmission. Cobalt can also chelate lipoic acids, impairing oxidation of pyruvate or fatty acids. In addition, cobalt may inhibit DNA repair by interacting with zinc finger DNA repair proteins, and has also been shown to inhibit heme synthesis and glucose metabolism. Cobalt may activate specific helper T-lymphocyte cells and interact directly with immunologic proteins, such as antibodies (IgA and IgE) or Fc receptors, resulting in immunosensitization. Radioactive cobalt damages DNA, RNA, and lipids through ionizing events. (L29)

Cobalt is absorbed though the lungs, gastrointestinal tract, and skin. Since it is a component of the vitamin B12 (cyanocobalamin), it is distributed to most tissues of the body. It is transported in the blood, often bound to albumin, with the highest levels being found in the liver and kidney. Cobalt is excreted mainly in the urine and faeces. (L29)

Cobalt-59 is the naturally occurring stable form of cobalt. Of the 9 major radioactive isotopes, only Co-57 and Co-60 have half-lives longer than 80 days. Cobalt-60 is formed by neutron activation in nuclear reactors and particle accelerators. [Argonne] Co-60 is used in medicine for instrument sterilization and radiation therapy for cancer; Used in industrial radiography and irradiation of food and grain; [Waltar, Appendix A-D]

Radioactive cobalt is used for commercial and medical purposes, such as for sterilizing medical equipment and consumer products, radiation therapy for treating cancer patients, manufacturing plastics, and irradiating food. (L29)