Drinking water and endemic gastrointestinal illness

A Systematic Review of the Time Series Studies Addressing the Endemic Risk of Acute Gastroenteritis According to Drinking Water Operation Conditions in Urban Areas of Developed Countries

Time series studies (TSS) can be viewed as an inexpensive way to tackle the non-epidemic health risk from fecal pathogens in tap water in urban areas. Following the PRISMA recommendations, I reviewed TSS addressing the endemic risk of acute gastroenteritis risk according to drinking water operation conditions in urban areas of developed countries. Eighteen studies were included, covering 17 urban sites (seven in North-America and 10 in Europe) with study populations ranging from 50,000 to 9 million people. Most studies used general practitioner consultations or visits to hospitals for acute gastroenteritis (AGE) as health outcomes. In 11 of the 17 sites, a significant and plausible association was found between turbidity (or particle count) in finished water and the AGE indicator. When provided and significant, the interquartile excess of relative risk estimates ranged from 3–13%. When examined, water temperature, river flow, and produced flow were strongly associated with the AGE indicator. The potential of TSS for the study of the health risk from fecal pathogens in tap water is limited by the lack of specificity of turbidity and its site-sensitive value as an exposure proxy. Nevertheless, at the DWS level, TSS could help water operators to identify operational conditions most at risk, almost if considering other water operation indicators, in addition to turbidity, as possible relevant proxies for exposure.

A time series study of gastroenteritis and tap water quality in the Nantes area, France, 2002-2007

In the Nantes area, 410,000 inhabitants are supplied with water pumped from the Loire River. The treatment of this water is carried out through a process of complete clarification and disinfection. During the study period (2002-07), the quality of drinking water complied with European microbial standards and mean turbidity in finished water was 0.05 NTU (nephelometric turbidity units). We aimed to characterize the link between produced water turbidity and other operational data and the incidence of acute gastroenteritis (AGE) in the Nantes area. The daily number of medical prescriptions for AGE was drawn from the French national health insurance system's drug reimbursement data. We modeled this time series using Poisson regression within the framework of a Generalized Additive Model. We showed that an interquartile range turbidity degradation (0.042-0.056 NTU) was connected to a 4.2% (CI95=(1.5%; 6.9%)) increase in the risk of AGE in children and a 2.9% (CI95=(0.5%; 5.4%)) increase in adults. The slope of the turbidity risk function was higher during both high- and low-water conditions of the river. High values of daily flow of produced water were also associated with higher endemic levels of AGE.

Drinking water consumption patterns in British Columbia: an investigation of associations with demographic factors and acute gastrointestinal illness

A cross-sectional telephone survey was performed in the province of British Columbia, Canada, to investigate drinking water consumption patterns and their associations with various demographic characteristics and acute gastrointestinal illness (AGI). Water consumption included plain water and water used in the preparation of cold beverages. The median amount of water consumed daily was four-250 mL servings (1.0 L), although responses were highly variable (0 to 9.0 L). Alternative water use was common: bottled water was the primary source of drinking water (i.e. >or=75% of the total daily water intake) for 23% of respondents and 47% of households used in-home water treatment methods. Approximately 10% of respondents reported an episode of AGI (vomiting or diarrhea) in the previous 4-week period. Such illness was associated with age (continuous variable in years, OR=-0.98), sex (male vs. female, OR=0.8) and the amount of water consumed (continuous variable in 250-mL servings, OR=1.06); however, a causal relationship with water consumption cannot be established based on this study alone. Overall, the associations of drinking water patterns with age, sex, education, and household income serve as important reminders to researchers and public health professionals of the non-uniform nature of drinking water consumption, and indicate potential differences in exposure to waterborne hazards in this population.

The association between drinking water turbidity and gastrointestinal illness: a systematic review

Background

Studies suggest that routine variations in public drinking water turbidity may be associated with endemic gastrointestinal illness. We systematically reviewed the literature on this topic.

Methods

We searched databases and websites for relevant studies in industrialized countries. Studies investigating the association between temporal variations in drinking water turbidity and incidence of acute gastrointestinal illness were assessed for quality. We reviewed good quality studies for evidence of an association between increased turbidity and gastrointestinal illness.

Results

We found six relevant good quality studies. Of five studies investigating effluent water turbidity, two found no association. Two studies from Philadelphia reported increased paediatric and elderly hospital use on specific days after increased turbidity. A fifth study reported more telephone health service calls on specific days after peak turbidity. There were differences between studies affecting their comparability, including baseline turbidity and adjustment for seasonal confounders.

Conclusion

It is likely that an association between turbidity and GI illness exists in some settings or over a certain range of turbidity. A pooled analysis of available data using standard methods would facilitate interpretation.

Changes in the incidence of gastroenteritis and the implementation of public water treatment

There are few data available on the incidence of endemic waterborne disease in the developed world. This study aims to determine if there was a measurable decline in gastroenteritis related faecal specimens following the introduction of water treatment. The rate of faecal specimens for gastroenteritis was obtained for 17 communities one year before and after the introduction of water treatment in two states of Australia between 1992 and 1996. Of these 17 systems, 10 had filtration added to existing disinfection, while seven had both disinfection and filtration or disinfection alone added to no existing treatment. The rate of faecal sampling varied from a reduction of 55% to an increase of 198%. Large changes in water quality parameters occurred following treatment but there was no significant correlation between these changes and changes in the rate of faecal specimens. In this study there was no consistent change in gastrointestinal related faecal specimens despite marked changes in water quality. This suggests that the reduction in endemic gastrointestinal disease as a result of the introduction of water treatment was small as a percentage of all gastroenteritis. However, water treatment remains essential to protecting public health.