Study Finds No Difference Between Tap and Filtered Water in Preventing Gastrointestinal Illness

The University of California at Berkeley, the United States Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC), and American Water recently announced the results of a year-long water evaluation trial study. The goal of the $3 million research project mandated by Congress was to evaluate whether healthy people contract gastrointestinal illness by drinking tap water in homes served by well-run water districts. The research found no evidence that gastrointestinal illness was transmitted.

This research represents the largest epidemiological study of drinking water in the United States. It examined the water supplied by American Water subsidiary Iowa American Water, which operates the Davenport treatment plant that was involved in the study. The plant was selected because the water meets or surpasses all federal guidelines and safety standards. It also serves a large population, tapping into the Mississippi River as its source of supply.

The study involved installing a microfilter and ultraviolet treatment device on the kitchen faucet of 450 healthy households. The participants were unaware that half of the devices installed were active filters and the other half were inactive placebo devices that were identical to the active filters. In the randomized and blinded intervention trial, researchers found no significant reduction in ill effects for those who used the home-filtered water compared with those who used the placebo device. The UC Berkeley-led research team included scientists from the EPA and the CDC.

After collecting 300 million data points, the American Water facility found no indication that a public health problem existed. "We have been delivering safe, high quality water to customers of American Water for over 100 years," stated Dr. Mark LeChevallier, director of research for American Water. "Our facility provides excellent water service to the residents of Davenport, and we're proud the study reflected this in their findings." American Water noted that the amount of analytical work done in this study far surpassed the level of scrutiny experienced by any other water system.

During this study, American Water was also able to rely on the advanced analytical and research capability available to a company-wide central Water Quality and Control Research Laboratory in Belleville, Illinois. American Water's Belleville Labs are recognized as the best in the United States and among the best in the world. The Belleville Labs were also used to monitor a concurrent $635,000 research project that examined water samples from the Mississippi River, the American Water treatment plant and distribution system in Iowa, and the household taps.

"What our study suggests is that if your tap water comes from a well-run water facility, where the water exceeds government treatment guidelines, there does not seem to be a health benefit from using an in-home water treatment device," stated John Colford, associate professor of epidemiology at UC Berkeley's School of Public Health and principal investigator of the study.

Dr. Tim Wade, the project director for the study while he was a Ph.D. student in epidemiology at UC Berkeley, stated, "We only conducted the test in one water treatment system, which is recognized as one of the best in the country, so we would need to do further tests before we generalize these results to other utilities." Wade is now a post-doctoral researcher at the EPA.

Source: American Water