Medical and hygienic assessment of influence of nitrates from decentralized water sources on cardiovascular and circulation systems morbidity

Abstract

Aim. To analyze the levels of nitrate pollution of decentralized water supply sources in the settlements of Lviv region, and to investigate their influence on the formation of morbidity of the cardiovascular and circulation system among the adult population of the region. Materials and Methods. The study was conducted according to the results of monitoring the nitrate content (mg / dm3) in the decentralized water supply sources for the period of 2012-2018 and the morbidity of the cardiovascular and circulation system of the adult population of 20 districts of Lviv region during 2012-2016. The assessment of health hazards for the adult population of Lviv region from consumption of nitrate-contaminated drinking water was carried out in accordance with the risk assessment methodology based on the calculated hazard coefficients (HQ). The results were processed by traditional methods of variation statistics using licensed computer programs Microsoft Excel and Statistica 10.0. Results and Discussion. The laboratory survey covered 2212 (2012) - 2468 (2018) sources of decentralized water supply in Lviv region. There is a clear tendency of increase in the level of nitrate contamination of the drinking water. Excessive nitrate content was found in 18.6-21.7% of individual sources, 9.9-10.5% of public wells and 12.6-13.3% of public captures. The highest concentrations and the highest percentage of excesses were registered in Mykolaiv, Zhovkva, Zolochiv, and Pustomyty districts, and the smallest of excess nitrates was recorded in Turka, Sambir and Staro-Sambir districts. The average excess nitrate content in the most polluted areas was in the range of 3.3-8.0 MAC, which corresponds to concentrations at 165-400 mg/dm3. The highest rates of cardiovascular morbidity and circulatory system were registered in areas where the population uses mainly decentralized water sources and cases were recorded of significant excess of nitrates in drinking water. The statistical analysis found positive correlation connections between the development of ischemia (moderate, r=0.49, p<0.05), angina pectoris (average, r=0.77, p<0.05), and hypertension (severe, r=0.99, p <0.05) and nitrate content in the drinking water. The determination coefficients were 23.08%, 59.58% and 98.01%, respectively. According to the results of the regression analysis, an adequate mathematical model was constructed to predict the probable development of this pathology among the adult population of the region. An assessment of the health hazard for adults consuming drinking water contaminated with nitrates indicates a threat of increased non-infection morbidity, including that of cardiovascular and circulation system, namely an increase in the average (HQ 1-5) risk of nitrates at 1.8-5.0 MAC to high (HQ 5-10) - at their concentration of 5.9-8.0 MAC. Conclusions. The solution to the problem of reducing nitrate pollution of drinking water should be included amongthe most important issues not only in the field of environmental protection, but also the protection of public health. Improving the environment will help reduce the load on the healthcare system in terms of preventing and treating cardiovascular disease. Keywords: nitrates, drinking water, cardiovascular diseases, diseases of the circulatory system