It is demonstrated that arseniasis in some zones in the Earth is an environmental phenomenon, which is affected by human activity. Such poisoning takes place mainly in residential areas near high-arsenic geological bodies, mineral deposits or in the lower reaches of the rivers passed them. Human activity in mining industry is an important active medium for the immigration of dangerous elements. Water is the most important conveying medium for arsenic. Its removal and changing are affected by the geochemical law and local hydrological state. The elements similar to arsenic in geochemical habits should be paid attention to, especially their joint actions and biochemical effects of valences of arsenic in human bodies.