Copyright © 2005 by the Johns Hopkins Bloomberg School of Public Health
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A Randomized, Controlled Trial of In-Home Drinking Water Intervention to Reduce Gastrointestinal Illness
1 Centers for Occupational and Environmental Health and Family and Community Health, University of California, Berkeley, School of Public Health, Berkeley, CA.
2 National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Chapel Hill, NC.
3 Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, GA.
4 Office of Groundwater and Drinking Water, US Environmental Protection Agency, Washington, DC.
5 US Environmental Protection Agency National Homeland Security Research Center, Cincinnati, OH.
6 University of California, Berkeley Survey Research Center, Berkeley, CA.
7 Division of Biostatistics, University of California, Berkeley, School of Public Health, Berkeley, CA.
Trials have provided conflicting estimates of the risk of gastrointestinal illness attributable to tap water. To estimate this risk in an Iowa community with a well-run water utility with microbiologically challenged source water, the authors of this 20002002 study randomly assigned blinded volunteers to use externally identical devices (active device: 227 households with 646 persons; sham device: 229 households with 650 persons) for 6 months (cycle A). Each group then switched to the opposite device for 6 months (cycle B). The active device contained a 1-µm absolute ceramic filter and used ultraviolet light. Episodes of "highly credible gastrointestinal illness," a published measure of diarrhea, nausea, vomiting, and abdominal cramps, were recorded. Water usage was recorded with personal diaries and an electronic totalizer. The numbers of episodes in cycle A among the active and sham device groups were 707 and 672, respectively; in cycle B, the numbers of episodes were 516 and 476, respectively. In a log-linear generalized estimating equations model using intention-to-treat analysis, the relative rate of highly credible gastrointestinal illness (sham vs. active) for the entire trial was 0.98 (95% confidence interval: 0.86, 1.10). No reduction in gastrointestinal illness was detected after in-home use of a device designed to be highly effective in removing microorganisms from water.
drinking; epidemiologic studies; gastrointestinal diseases; intervention studies; randomized controlled trials; water; water supply
Abbreviations: CDC, Centers for Disease Control and Prevention; CI, confidence interval; EPA, US Environmental Protection Agency; HCGI, highly credible gastrointestinal illness.
Correspondence to Dr. John M. Colford, Jr., University of California, Berkeley, School of Public Health, Division of Epidemiology and Public Health Biology, 140 Warren Hall #7360, Berkeley, CA 94720 (e-mail: jcolford{at}socrates.berkeley.edu).
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