Respiration of metal induced rhabdomyosarcomata

Mutagenicity, carcinogenicity and teratogenicity of cobalt metal and cobalt compounds

Cobalt metal and cobalt compounds are extensively used for the production of high-temperature alloys, diamond tools, cemented carbides and hard metals, for the production of various salts used in electroplating and as catalysts, drying agents in paints, additives in animal feeds and pigments. Cobalt oxides are used not only in the enameling industry and for pigments, but also in catalytic applications. There is no indication that cobalt metal and cobalt compounds constitute a health risk for the general population. Allergic reactions (asthma, contact dermatitis) can be induced by certain cobalt compounds. Interstitial fibrosis has also been observed in workers exposed to high concentrations of dust containing cobalt, tungsten, iron, etc., mainly in the cemented carbides and the diamond-polishing industries. Several experiments have demonstrated that single or repeated injections of cobalt metal powder or some forms of cobalt salt and cobalt oxide may give rise to injection site sarcoma in rats and in rabbits but the human health significance of such data is questionable. Intratracheal administration of a high dose of one type of cobalt oxide induces lung tumors in rats but not in hamsters. In the latter long-term inhalation of cobalt oxide (10 mg/m3) did not increase the incidence of lung cancer. The human data are too limited to assess the potential carcinogenic risk for workers. Co2+ interacts with protein and nucleic acid synthesis and displays only weak mutagenic activity in microorganisms. Some cobalt salts have been reported to enhance morphological transformation of Syrian hamster embryo cells. Cobalt chloride displays some limited mutagenic activity in yeast and some cobalt compounds are able to produce numerical and structural chromosome aberrations in plant cells. Cobalt and its salts appear to be devoid of mutagenic and clastogenic activity in mammalian cells. Cobaltous acetate and cobaltous chloride have not been found to be teratogenic in hamsters and rats respectively.

Cobalt exposure and cancer risk

Cobalt is a technically important metal, used mainly as a binder in the hard-metal industry and as a constituent of many alloys. Cobalt compounds are used as drying agents in paints and laquers. Since ancient times, cobalt compounds have been used as coloring agents for pottery, ceramics, and glass. Soluble cobalt salts interfere adversely with cell division, bind irreversibly to nucleic acids in the cell nucleus, induce chromosome aberrations in plants, and are weakly mutagenic in some in vitro tests with cultured animal cells, bacteria, and yeast. Injections or implantation of cobalt metal, cobalt alloys, and cobalt compounds induced local and sometimes metastasizing sarcomas in rats, rabbits, and mice. Mouse is the least susceptible animal. The only published inhalation study with hamsters exposed to CoO aerosols remained non-positive. Indication of possible carcinogenic effects of cobalt alloys or compounds in human populations has arisen from medical use, in hard-metal industries, and at cobalt production. Unfortunately, confounding by nickel and arsenic is a major problem, and the size of most of the investigated populations has been rather small, so none of the investigations alone gives sufficient evidence of a carcinogenic effect in humans, but taken together there is an indication of a carcinogenic potential that should be explored further.

Carcinogenicity, mutagenicity and teratogenicity of nickel

Nickel is widely used in the metallurgical industry, and although not released extensively into the environment, may represent a hazard to human health. Owing to their low absorption from the gastrointestinal tract, nickel compounds, except nickel carbonyl, are essentially non-toxic after ingestion. Epidemiological investigations and experimental studies have demonstrated that certain nickel compounds are extremely potent carcinogens after inhalation, but also that the carcinogenic risk is limited to conditions of occupational exposure. The relatively small number of mutagenicity studies performed up to now do not yet allow definite conclusions as to whether nickel is mutagenic. Nickel can cross the placenta and has embryotoxic and teratogenic properties. The principal hazard of nickel to man, beside its carcinogenicity, however, is its ability to provoke reactions of sensitization.