Ntroduction. The assessment of water quality and safety of centralized water supply systems in the Primorsky Krai was carried out in order to assess hygiene levels of public health risks associated with drinking water from the distribution network. Material and methods. The data of laboratory studies on sanitary and chemical parameters in drinking water of the distribution network of the Primorsky region were used. Hygienic assessment of drinking water was carried out according to regulatory requirements, the effect of summation of biological effect was calculated. The work used methodological recommendations for calculating the index of chemical water pollution and the utility coefficient, as well as a guide for assessing the health risks of the population when exposed to chemicals of a non-carcinogenic and carcinogenic nature. Non-carcinogenic and carcinogenic risks were calculated for all potable water of centralized water supply based on the average daily intake dose and the reference dose of chemicals supplied with drinking water. The risk profile for carcinogenic and non-carcinogenic effects was achieved by comparing exposure levels with reference concentrations (safe) for human health. The risk profile for the combined effects of chemical compounds is based on the calculation of the hazard index (HI). A study on carcinogenic risk was carried out for substances that are identified as carcinogens according to the classification of an international agency for the study of cancer. For the analysis and statistical processing of information, the program "MS Excel" was used. Results. An assessment of the sanitary and epidemiological safety of centralized systems of domestic and drinking water supply in the region showed that the highest contribution to poor health is made by the content of arsenic, nitrates, iron, silicon, and petroleum products in drinking water. According to the values of hazard indices, the skin and mucous membranes, the central nervous system, the immune system, the endocrine system, the circulatory and digestive organs are exposed to adverse effects from chemicals in drinking water. The individual carcinogenic risk ranges from negligibly small to the upper limit of acceptable carcinogenic risk. Assessment of the potable water value indicator revealed a deficit situation in calcium, sodium, fluorine and general mineralization of water. The risk assessment for arsenic, tetrachlorethylene, and chloroform, which have carcinogenic properties and are the most important pollutants of drinking water, has shown that the individual risk levels for these substances are within the first and second ranges, which corresponds to the allowable and maximum allowable risk. Discussion. Arsenic concentration in adults was found to be not detected with risks greater than one, while for children, the non-carcinogenic risk from arsenic exceeded the level of safe exposure (HQ> 1), because children are more susceptible to toxic substances due to their relatively large volume of respiration and the rate of gastrointestinal absorption (due to greater permeability of the intestinal epithelium), and also due to the immature system of detoxification enzymes and a relatively lower rate of excretion of toxic chemicals. According to the level of non-carcinogenic risk for children, nitrates follow arsenic. Nitrates have a hypoxic effect, increasing the concentration of the irreversible form of hemoglobin - methemoglobin. The toxicity of nitrates is related to their transformation into the human body into nitrosamines. As a result, the child's organism responds more sharply than in adults to the presence of chemicals in the water. The general mineralization of drinking water is one of the integral index of the quality of drinking water. Calcium and magnesium deficiency can be an independent risk factor for the development of various diseases and manifest pathologies of the cardiovascular system: coronary heart disease, hypertensive disease, myocardial infarction, etc. The tap water is known to be is not overloaded with carbonates, since they can lead to spoilage of water pipes. Therefore, to enrich the water with calcium and magnesium, the technology of creating bottled water uses mineral additives, which means that such water can become an additional source of minerals. Conclusion. Sanitary and hygienic assessment of centralized systems of domestic and drinking water supply in the Primorsky Territory has shown that the quality of drinking water depends on the concentration of arsenic, nitrates, iron, silicon and petroleum products. It should be noted that with the daily use of water from the distribution network throughout life, the likelihood of developing harmful effects on the health of adults and children is insignificant.
CONTRIBUTION TO THE HYDROCHEMICAL KNOWLEDGE OF AQUIFERS IN THE DEPARTMENT OF TANDJILE-EAST, SOUTHERN CHAD
