Hygienic assessment of dangerous chlorites in drinking water treated with chlorine dioxide and the risk of its consumption to the health of the population

Abstract

Today, chlorine dioxide has begun to be more widely implemented in water treatment technologies on river running water systems of Ukraine. Chlorine dioxide is used in traditional water treatment technology for both primary and secondary water treatment on the Dnipro running water system in Kyiv. Objective – to analyze the results of the content of dangerous chlorites in tap drinking water of certain districts of the city of Kyiv, and calculate and assess non-carcinogenic risk of this drinking water for human health. It was shown that in the drinking water from the running water networks of Svyatoshynskyi, Shevchenkivskyi, Obolonskyi and Podilskyi districts of the city, into which it enters after treatment with chlorine dioxide from the Dnipro running water system, the levels of chlorites were the lowest in winter and spring. In summer, the concentrations of chlorites in the water from the studied networks were the highest and averaged from 0.32 to 0.45 mg/dm3. In autumn, chlorites in the water from these systems were at the level of 0.22-0.28 mg/dm3. In spring (May) and especially in summer, the levels of chlorites in drinking water, according to average data, exceeded the national hygienic standard (0.2 mg/dm3) by 1.5-2 times, but they were never higher than the chlorite standard (0.7 mg/dm3) recommended by WHO. Our analysis of sanitary-chemical and microbiological indicators in drinking water showed that the water is characterized by high quality and safety during the entire period of observation. The risk assessment of the development of non-carcinogenic effects for the oral route of intake of chlorites with drinking water from the specified water networks based on average annual data showed the value of the danger coefficient (HQ) at the level of 0.24-0.38, that is, it was lower than 1.0. The danger coefficient for chlorite content in drinking water was also determined at the level of 0.2 mg/dm3 and 0.7 mg/dm3. According to this indicator, the lifetime use of drinking water with a chlorite content of 0.2 mg/dm3 and even 0.7 mg/dm3 does not pose a threat to human health, since the danger coefficient is within 1.0, which is a permissible (acceptable) risk by degree of danger. Thus, the use of chlorine dioxide in traditional water treatment technology ensures high quality and safety of drinking water in terms of microbiological and sanitary-chemical indicators. There is a periodic (mainly in summer) excess of chlorite content in drinking water in relation to the national standard (0.2 mg/dm3), but its level was never higher than the standard recommended by WHO (0.7 mg/dm3). It has been shown that the existing levels of chlorites in drinking water and its use with such a toxic load do not pose a threat to human health.