Studies of the circulation of mercury in various objects of the environment (water of reservoirs, bottom-reservoir sediment, flood-plain soil and the soil of agricultural lands irrigated with the water from the river and canal, water organisms, products of plant-growing etc.) in areas located downwards from the points of long-term discharge into the ecosystem of mercury with industrial wastes have been carried out, with the aim to establish real stress on the organism of people living within the basin of the reservoir. Discharge of mercury into water sources has been found with the warmed-up and industrial waste waters following mechanical and biological treatment at the plant producing synthetic rubber, with filtration waters from slime tanks and also secondary contamination of the water with mercury coming from bottom--reservoir sediment, and quantitative parameters of circulation of the chemical in the ecosystem of the reservoir basin. Intake of mercury into human organism under the conditions of formation of biogeochemical provinces in the reservoir basin (through water, fish, agricultural products) leads to the increase of the level of morbidity of the nervous system and a number of other diseases, which is associated both with the specific effects of the element and with the non-specific influence it produces as a result of decrease of general resistance of the organism.