Daily variations in effluent water turbidity and diarrhoeal illness in a Russian city.

To assess an association between temporal variations in drinking water quality and gastrointestinal (GI) illness, a cohort study involving 100 randomly selected families (367 individuals) was conducted in the city of Cherepovets, Russia from June through November 1999. Participants maintained daily diaries of gastrointestinal symptoms, water consumption and other behavioural exposure variables, while daily effluent water quality data were provided by the water utility. The cumulative incidence rate of self-reported gastrointestinal diseases, 1.7 cases per person-year, was almost two orders of magnitude higher than that of officially reported GI infections in the city. An interquartile range increase in effluent water turbidity of 0.8 Nephelometric Turbidity Units was associated with a relative risk of self-reported GI illness of 1.47 (95% Confidence Interval 1.16, 1.86) at a lag of 2 days after control for daily rate of consumption of non-boiled tap water, behavioural covariates, day of the week and a seasonally-related linear trend. In the analysis by subsets of study participants stratified by non-boiled tap water consumption, no statistically significant associations between turbidity and GI illness were found for the study participants who always boiled their drinking water. For individuals who drank non-boiled tap water, statistically significant associations between turbidity and GI illness were detected at lags 1, 2 and 7 days.

Deterioration of drinking water quality in the distribution system and gastrointestinal morbidity in a Russian city.

Few studies have been conducted in Russia to assess the relationship between drinking water quality and gastrointestinal (GI) infections. In the city of Cherepovets, effluent water at the treatment plant usually meets the country's hygienic standards. To provide protection against secondary water contamination in the distribution system, concentrations of total residual chlorine in effluent water are maintained#10; at levels from 1 to 2 mg x l(-1). However, residual chlorine concentrations rapidly decline in the distribution system and rechlorination is not practiced. Some areas of the city routinely have very low residual chlorine at taps and little protection against secondary microbiological contamination of water in pipelines. A cross-sectional epidemiological study was conducted in Cherepovets to assess an association between decline in residual chlorine concentrations and risk of GI illness. This study included water quality monitoring and an extensive questionnaire survey of city residents. The results demonstrated a consistent spatial pattern of free chlorine decline in the distribution system. An interquartile range variability in free residual chlorine decline (0.22 mg x l(-1)) was associated with 1.42 (95% confidence interval (CI) = 1.05, 1.91) relative risk of self-reported gastrointestinal illness after control for socioeconomic, hygienic and demographic parameters.

Contamination of water supplies with Cryptosporidium parvum and Giardia lamblia and diarrheal illness in selected Russian cities.

Cryptosporidium parvum and Giardia lamblia are important agents of waterborne diarrheal illness worldwide. While giardiasis is routinely diagnosed in Russia with a chemical staining technique, data on the prevalence of cryptosporidiosis are scarce. Monitoring of the respective parasites in water supplies in Russia is very limited. A health survey conducted in the city of Cherepovets and three other cities in the European part of Russia using enzyme-linked immunosorbent assays (ELISA) demonstrated that 6.9% of diarrheal patients tested had C. parvum antigens in their fecal samples; 9.4% had G. lamblia antigens. A survey of occurrence of these parasites in water supplies in Cherepovets and seven other cities demonstrated that source and finished water samples from several of these cities were contaminated with either C. parvum oocysts or G. lamblia cysts. The surveys were not designed to assess associations between presence or concentrations of C. parvum and G. lamblia in water and related gastrointestinal diseases in exposed populations. Rather, the goals were to demonstrate the presence of disinfection-resistant protozoan parasites in untreated and treated waters, and the importance of these pathogens as causative agents of diarrheal illnesses in a number of Russian cities.