Press Releases

1999 Releases

Treated Drinking Water Not Safe Enough: Harvard Study Shows Elderly Particularly Sensitive to Waterborne Hazards

For immediate release: December 15, 1999 

Boston, MA--Ten percent of hospital admissions for people over age 65 for gastrointestinal (GI) illness can be blamed on harmful microbes in drinking water--this in a city with state-of-the-art water treatment, found researchers from the Harvard School of Public Health.

The study, in the January issue of the Journal of Epidemiology and Community Health, found an association between day-to-day variations in drinking water turbidity in Philadelphia and variations about a week later in the number of Medicare hospital admissions for GI illness. Turbidity--a cloudiness caused by suspended particles--was used as an indicator of potential risk of contamination from harmful microbes in water.

The research confirmed the findings of the same Harvard investigators two years ago, when they looked at emergency room visits of children for GI illness in relation to episodes of increased water turbidity. Children and the elderly are among the groups most susceptible to infectious GI illness.

Philadelphia obtains its drinking water from the highly contaminated rivers that flow through the city and treats that water in sophisticated treatment plants. However, as an editorial accompanying the paper points out, many pathogens known to cause GI illness are resistant to chlorine, the primary disinfectant used in the plants. The Philadelphia water system met federal water standards throughout the two-year study period.

This study and others, said the authors, suggest that "some of what has been understood as endemic GI illness in the U.S. is actually waterborne infectious disease."

Study author Joel Schwartz, associate professor of environmental health at the Harvard School of Public Health, said the 10 percent of GI illness attributed to the water is a low estimate, "because our measure of water quality is crude, and poorer measures of exposure lead to underestimates in risk."

If Philadelphia, with a high-quality treatment system, is having health problems, said Schwartz, other cities with less sophisticated technology, "are likely to be having problems too." An initially cleaner water supply is important, said Schwartz. "Drinking river water is riskier than drinking from protected water supplies."

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