Drinking water turbidity and gastrointestinal illness in the elderly of Philadelphia

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Abstract
STUDY OBJECTIVE To investigate the association between drinking water quality and gastrointestinal illness in the elderly of Philadelphia. DESIGN Within the general population, children and the elderly are at highest risk for gastrointestinal disease. This study investigates the potential association between daily fluctuations in drinking water turbidity and subsequent hospital admissions for gastrointestinal illness of elderly persons, controlling for time trends, seasonal patterns, and temperature using Poisson regression analysis. SETTING AND PARTICIPANTS All residents of Philadelphia aged 65 and older in 1992–1993 were studied through their MEDICARE records. MAIN RESULTS For Philadelphia's population aged 65 and older, we found water quality 9 to 11 days before the visit was associated with hospital admissions for gastrointestinal illness, with an interquartile range increase in turbidity being associated with a 9% increase (95% CI 5.3%, 12.7%). In the Belmont service area, there was also an association evident at a lag of 4 to 6 days (9.1% increase, 95% CI 5.2, 13.3). Both associations were stronger in those over 75 than in the population aged 65–74. This association occurred in a filtered water supply in compliance with US standards. CONCLUSIONS Elderly residents of Philadelphia remain at risk of waterborne gastrointestinal illness under current water treatment practices. Hospitalisations represent a very small percentage of total morbidity.