Metals, dangerous for life

There are several, but not all of them are adequately studied. We have to remember that some of the already described "useful" metals overdose turn into poison. To take at least such valuable for health and at the same time such a dangerous selenium. From this point of view it is similar to some extent arsenic.

Arsenic

Already in ancient times it was known as a medicine and as a poison. To date it is sometimes used in medicine. Acts firming, applied against anemia, increases appetite.
In the soil contains about 1 to 40 ppm of arsenic, but it could be much more if its compounds are sprayed with gardens and plantations. If the concentration of arsenic in soil, food, etc., will cross a certain limit is closer to toxic doses, then increase the number of deaths caused by cancer of the larynx, eyes, or leukemia (Berg and Burbank).
At the same time arsenic can serve as a good antidote when, for example, livestock (pigs, cows), dogs and poultry poisoned with high doses of selenium. In the experiments on mice, managed to reduce the incidence of cancer it is with the help of specially selected doses of arsenic.
In the body (mostly in hair and nails) is from 15 to 20 mg of arsenic. The richest source in the diet can be considered edible molluscs (lobster, lobster, shrimp, krill and so on) and several species of marine fish.