Our research goal was to assess health risks for population who consumed drinking water with specific chemical structure systematically and for a long time. Drinking water quality is determined by conditions existing in hydrogeochemical provinces where rocks and soils contain increased concentrations of such hazardous metals as chromium, nickel, lead, manganese, and iron. We showed that low frequency or even absence of nonconformity to hygienic standards for admixtures in drinking water doesn't fully guarantee its safety in complicated hydrogeochemical conditions. When certain carcinogenic admixtures (cadmium, chromium, nickel, arsenic, and lead) occur together in drinking water even in low concentrations, it can cause unacceptable population health risks. Drinking water taken in examined geochemical provinces in Perm region causes individual lifelong carcinogenic risk which is (under the worst exposure scenarios) equal to 4 • 10-3. It can be ranked as De manifestis Risk and requires immediate measures to be taken by those responsible to reduce it. Unacceptable non-carcinogenic risks are caused by joint concentrations of arsenic, strontium, and some other compounds in drinking water. The highest risks existing on the examined territories were detected in relation to gastrointestinal tract diseases (HI up to 10.9, basic risk factor is chromium and its compounds), musculoskeletal system diseases (HI up to 11.8, strontium as a basic factor), and central nervous system diseases (HI up to 11.8, basic factors are arsenic, manganese, and lead). Contributions made by various elements into overall risks were different in different provinces. In some cases, when a certain element occurs in the crust in hazardous concentrations, its contents in drinking water are not observed. We recommend organizations that deal with water supply and sanitary surveillance bodies to take into account peculiarities of a geochemical province and to include admixtures that are contained in the environment in high quantities into monitoring programs and laboratory research.

The high content of chemical elements in the sources of drinking water in addition to anthropogenic contamination may be due to the presence of the source in a particular geochemical provinces, creating the initially high background levels of chemicals of concern in water. It was found that among 14 geochemical provinces of Perm region in 4 there was the excess of the maximum allowable concentrations in water sources: the manganese to 2.3 MAC and strontium to 17.0 MAC. It is shown that, despite the use of modern methods of water treatment used in the economic activity and for the purpose of drinking water, in drinking water after treatment manganese, fluorine, strontium, beryllium and Nickel exceeding to 20.0 MPC, substance characteristic water sources within the boundaries of the geochemical provinces, are recorded. The event production control does not always include a program of sampling on the specific geochemical provinces of the substance, such as boron, bromine, barium, etc. In the course of the assessment of health risk from consumption of drinking water from sources located within the boundaries of geochemical provinces obtained that the coefficients of the danger (HQ) exceeded the acceptable level to 2.2 times for a number of substances, and the hazard index (HI) of health disorders exceeded the permissible level up to 2.5 times. The total contribution of the typical geochemical provinces of substances has reached 100,0 % for some organs and target systems.