Arsenic (74,9 a.m.u.) – one of the most recognized toxic metals. Present in several toxic and non-toxic forms. Non-organic compounds As3+ – As (III) and As5+ – As (V) are toxic; last one is the most toxic. Non-toxic forms of organic arsenic are present in some kinds of food; mostly in sea products. Low concentrations of arsenic could supposedly be considered as conditionally essential nutrient. It interacts with thiol-containing proteins, cysteine, glutathione, lipoic acid and affects oxidation processes in mitochondria.

Deficit (reported in experiments with animals) results in fertile disorders, misbirths, stillbirths, decrease of antitumor immunity; concentration of copper and manganese is increasing in organs and tissues in cases of arsenic deficit. Arsenic compounds are used in medicine. Non-organic compounds in small doses could contain in general tonic agents, medicinal water and mud. Organic compounds of arsenic are used as antibacterial and antiprotozoal drug.

Sources of arsenic intoxication could be industrial treatment or intake of pesticides. In cases of heavy intoxications, mostly indicative are gastro-intestinal symptoms, possible spasms and coma, respiration and heartbeat disturbances. Chronic exposure causes damage of skin and mucosa, disorders in nervous system (neurologic pain in feet, weakness, sensibility disorders), disorders of intestinal tract. Cases of cancer caused by arsenic are reported.

In case of intake of toxic arsenic forms As5+ and As3+ they are often excreted with urine in unchanged form, partly metabolising in less toxic methylated metabolite arsino-methyl, arsino-dimethyl), and partly absorbed and deposed in tissues and cells, interacting with phosphates. Toxicity of non-organic arsenic is related to the competition with phosphates and inhibition of enzymes, participating in energetic processes and sulfhydryl group protein binding. This is the reason why arsenic is called “thiol poison”.

When arsenic is intaken, increase of its concentration in blood is monitored only within 4 hours. Research of blood for presence of arsenic is used only to establish the fact of acute intoxication. Urine could be used as a specimen for investigation, as long as arsenic is being excreted from body mostly by kidneys and is present in urine in concentrated condition. Concentration of non-organic As5+ andAs3+ in urine is highest in 10 hours after the intake and is back to normal in 20 – 30 hours. Concentration of methylated metabolites in urine is highest in 40 – 60 hours and is back to normal on 6th – 20th day after arsenic was intaken. Organic arsenic is completely excreted from the body within 1 – 2 days after intaken.

Separated establishment of toxic non-organic arsenic and non-toxic organic arsenic requires very special methods. Often moderate increase of arsenic excretion with urine is reasoned by the presence of its non-toxic organic forms, peculiar to sea products. Normal level of arsenic excretion with urine is 0 – 120 mcg/day. Arsenic has high affinity for keratin, this is the reason why concentration of arsenic in hair and nails is higher than in other tissues. Average hair growth speed is 0,5 cm/month. Hair specimens, cut near roots on the hind head allows to judge on the recent exposure of arsenic. Concentration of arsenic in hair higher than 1 mcg/g of dry mass indicates active exposition to arsenic.