Cobalt forms a number of organic and inorganic salts with the most stable oxidation numbers being +3 [Co(III)], and +2 [Co(II)]. Cobalt is an element that occurs naturally in many different chemical forms throughout our environment (Lison et al., 2001).Vitamin B12 contains 4% cobalt which confirms that this element is essential to man (Kim et al., 2008). Experimental studies confirmed that cobalt can not only interfere with DNA repair processes but can also cause direct induction of DNA damage
The toxicity of cobalt is relatively low compared to many other metals (Gal et al., 2008). Its toxic effect in higher concentrations affects mainly the lungs, leading to asthma, pneumonia and wheezing. Overdosing of cobalt (>5 mg/day) may lead to abnormal thyroid functions, polycythemia and overproduction of red blood cells
(erythropoiesis), with increased production of the hormone erythropoietin. There is also a risk of pulmonary edema, peripheral vascular thrombosis, optic nerve atrophy. Intranasal use of vitamin B12 includes symptoms such as headache, sore throat and rhinitis.