摘要：Objectives. We examined whether drinking untreated rainwater, a practice that is on the rise in developed countries because of water shortages, contributes to community gastroenteritis incidence. Methods. We conducted a double-blinded, randomized controlled trial in Adelaide, Australia. Sham or active water treatment units were installed, and participants recorded incidences of illness in a health diary for 12 months. The primary outcome was highly credible gastroenteritis (HCG; characterized by a specified number of loose stools or vomiting alone or in combination with abdominal pain or nausea in a 24-hour period), and we used generalized estimating equations to account for correlations between numbers of HCG events for individuals in the same family. Results. Participants reported 769 episodes during the study (0.77 episodes/person/year), with an HCG incidence rate ratio (active vs sham) of 1.05 (95% confidence interval [CI] = 0.82, 1.33). Blinding of the participants was effective (index = 0.65; 95% CI = 0.58, 0.72). Conclusions. Our results suggest that consumption of untreated rainwater does not contribute appreciably to community gastroenteritis. However, our findings may not be generalizable to susceptible and immunocompromised persons because these groups were specifically excluded from the study. Climate change and population growth have resulted in diminished potable water supplies globally. 1 In developed countries such as Australia, parts of Europe, and the United States, water restrictions and the promotion of alternative water sources, including rainwater, have reduced demands on water mains. However, several studies have shown significant variability in the microbial quality of stored rainwater: 75% of tanks were found to contain fecal and total coliforms. 2 – 6 Unlike conventional tap water, household rainwater supplies are usually untreated. Thus, the susceptibility of collected rainwater to contamination makes it a potential source of pathogenic microorganisms. In Australia, household rainwater tank usage increased 40% between 2004 and 2007. 7 , 8 Harvesting rainwater for drinking remains the choice of the consumer, but health authorities generally do not endorse consumption of untreated rainwater if a potable water system exists. 9 , 10 Statistics nevertheless show that 2.5% of persons living in urban Australia drink rainwater; Adelaide, in South Australia, has the highest proportion at 10.6%. 8 Increasing rainwater consumption, with its potential associated health risks from deliberate or inadvertent contamination, has created a need for research on rainwater quality and the health effects of rainwater usage. Some previous epidemiological studies have shown an association between rainwater consumption and illness, 11 although 1 South Australian study showed no significant difference in highly credible gastroenteritis (HCG) among consumers of rainwater and consumers of mains water, 12 and another suggested that rainwater consumption was protective. 13 HCG is characterized by a specified number of loose stools or vomiting alone or in combination with abdominal pain or nausea in a 24-hour period. Several randomized trials have been conducted to evaluate the effect of mains water on the incidence of gastroenteritis, 14 – 16 but no trials have been conducted on the effect of rainwater consumption. We therefore conducted a double-blinded, randomized, controlled trial to determine whether consumption of untreated rainwater contributes to community gastroenteritis incidence.
