Excessive cobalt exposure may occur in the hard metal industry, cobalt refineries, specialist alloy manufacture, magnet manufacturing, in the paint industry and in diamond tooling. Cobalt inhalation can lead to ‘hard metal disease’, respiratory sensitization, pneumonia, wheezing, and asthma. (reference)
Several agencies have recommended the following limits on airborne cobalt exposure:
Because it is not regulated at the point of absorption, cobalt can be toxic to humans when consumed in excessive quantities. Excesses can cause polycythemia (increased red blood cells), bone marrow hyperplasia, pancreatic failure or congestive heart failure and cardiomyopathy, and large doses interfere with iron absorption. Back in the 1960's, some breweries added cobalt to beer for foam stabilization. Some who drank large quantities of the beer experienced nausea, vomiting, and heart injury. However, heart injury was not seen in anemic people or pregnant women treated with cobalt. Animal studies have shown abnormal fetal development in animals exposed to high concentrations of cobalt during pregnancy.
The International Agency for Research on Cancer has determined that cobalt is a possible carcinogen to humans, but human studies are currently inconclusive. Animal studies show that cobalt causes cancer when placed directly into the muscle or under the skin, but not when the animals were exposed to cobalt in air, food, or drinking water. Skin contact with cobalt or some of its compounds can lead to allergic dermatitis.
The synthetic isotope 60Co, is used extensively as a tracer and in cancer radiotherapy, but must be handled carefully. Because it has a gamma ray emission rate 25 times that of radium, it poses a significant radiation exposure hazard when mishandled or released into the environment.
Cardiomyopathy is a serious disease in which the heart muscle becomes inflamed and doesn't work as well as it should. There may be multiple causes including viral infections. Cardiomyopathy can be classified as primary or secondary. Primary cardiomyopathy can't be attributed to a specific cause, such as high blood pressure, heart valve disease, artery diseases or congenital heart defects. Secondary cardiomyopathy is due to specific causes. It's often associated with diseases involving other organs as well as the heart. (reference)
Hyperplasia (or "hypergenesis") is a general term for an increase in the number of the cells of an organ or tissue causing it to increase in size. It may be due to any number of causes including (but not limited to) increased demand, chronic inflammatory response, hormonal dysfunctions, or neoplasia. (reference)
Polycythemia vera is an acquired disorder of the bone marrow that causes the overproduction of all three blood cell lines: white blood cells, red blood cells, and platelets. It is a rare disease that occurs more frequently in men than women, and rarely in patients under 40 years old. It is not known what causes polycythemia vera. The disease usually develops slowly, and most patients do not experience any problems related to the disease after being diagnosed. However, the abnormal bone marrow cells may begin to grow uncontrollably in some patients leading to acute myelogenous leukemia. (reference)