Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/20/2011
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Background: Groundwater supplies for drinking water are frequently contaminated with human gastrointestinal viruses. Stemming from this knowledge, the US EPA promulgated the Groundwater Rule, yet the number of illnesses in the nation that can be attributed to groundwater-borne viruses is unmeasured. The objective of the Wisconsin Water And Health Trial for Enteric Risks (WAHTER Study) was to estimate how much acute gastrointestinal illness is attributable to drinking water in groundwater-source communities that do not practice disinfection. Methods: Fourteen Wisconsin communities relying primarily on sandstone aquifers participated. Ultra-violet disinfection (UV) was installed on the communities’ wellheads in a randomized-intervention study design where in the first study year one-half of the communities had UV disinfection installed and the remaining communities were controls, and in the second year the UV units were swapped between groups so the intervention communities became controls and vice versa. Acute gastrointestinal illness (AGI) with and without the UV disinfection in place was measured from health diaries completed weekly by participating households within each study community (n = 673 households, 1786 people). Virus samples were collected monthly from eight households per community and viruses were quantified by real-time qPCR. Results: Among 1,204 tap water samples from 14 communities, 287 (24%) were positive for at least one virus type and 41 (3%) were positive for two or more types. Tap water virus concentrations were significantly associated with AGI incidence rates; those communities with the highest virus concentrations in their tap water also had the highest rates of illness. UV disinfection reduced AGI incidence in adults and children less than 5 years old by 13%. In other words, for these two age groups, 13% of their illnesses resulted from drinking non-disinfected groundwater. During one three-month period of the study, when many of the municipal wells were contaminated with noroviruses, the fraction of AGI in the communities resulting from drinking non-disinfected water was 29%. As there was no residual disinfectant, when UV disinfection was installed and eliminating viruses from the groundwater, any viruses measured downstream at household taps must have entered the distribution systems from pipe intrusions or other types of backflows during transient negative pressure events. Using a risk assessment approach, we estimate 2% to 4% of the AGI in the communities resulted from direct contamination of the distribution systems. Water main construction was the activity most strongly associated with virus contamination of the distribution systems. Conclusion: The majority of public water systems in the US produce drinking water without disinfection, suggesting the population served is exposed to waterborne viruses and the illnesses that can result.