Iron is an assential element for the growth, division, differentiation and functioning of any cell in the body. Iron is virtually important for human and danger at the same time, because with excessive accumulation it causes oxidative stress with formation of highly active oxygen radicals and reactive form of nitrogen that can destroy cell membranes, proteins, nucleic acids, reduce cell viability, with, according to modern concepts, can contribute to the development of many diseases (cardiovascular, rheumatic, gastrointestinal, neurodegenerative, oncological, metabolic and others), and also accelerate the aging process. Part 1 of this review discussed the issues of iron metabolism in human, including its regulation at the cellular and systemic levels, the intake, transport, use, accumulation and export of iron in cells, the role of the labile iron pool in the cytoplasm of cells and plasma non-transferrin bound iron. Data are provided on the causes, frequency and significance of iron overload in the formation of free radicals and the development of oxidative stress. Part 2 of the review provides information on diseases associated with iron overload as well as information on ferroptosis - a new type of iron-dependent regulated cell death. Attention is paid to the works of domestic authors, where it was found that prolonged use of drinking water with a high iron content is unfavorable for the population and leads to an increase in the overall incidence, the development of the diseases of the blood, skin and subcutaneous tissue, musculoskeletal system, digestive system, urogenital system, and allergic diseases. Separate publications are cited on the possibility of a negative effect of iron at concentrations in water of 0.3 mg/l and lower. The material of the review emphasizes the preventive significance of caution attitude to regulating iron in the water in the Russian Federation, where 1/3 of the population uses iron-containing water for drinking, and substantiate the feasibility of establishing a hygienic limit for iron in water not higher than 0.3 mg/l.