Study: Cold water as effective as hot to remove germs

Research suggests handwashing for 10 seconds is adequate enough to eliminate harmful bacteria.
By Amy Wallace  |  May 30, 2017 at 12:25 PM
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May 30 (UPI) -- Researchers at Rutgers University found that cool water is just as effective at removing bacteria in handwashing as hot water.

The study, published in the Journal of Food Protection, tested the effectiveness of bacteria removal in 21 participants washing their hands in 60, 79 and 100 degree water using 0.5 ml, 1 ml or 2 ml volumes of soap over a six-month period.

"People need to feel comfortable when they are washing their hands but as far as effectiveness, this study shows us that the temperature of the water used didn't matter," Donald Schaffner, a professor and extension specialist in food science at Rutgers, said in a press release.

The study findings may have an impact on the restaurant and food industry as current U.S. FDA guidelines, issued every four years, require plumbing systems at restaurants and food establishments deliver water at 100 degrees for handwashing.

"This study may have significant implications towards water energy, since using cold water saves more energy than warm or hot water," Schaffner said. "Also we learned even washing for 10 seconds significantly removed bacteria from the hands."

Water temperature has been debated for many years and many states interpret the FDA guidelines as a requirement to have water temperatures of 100 degrees, according to Schaffner.

"I think this study indicates that there should be a policy change," Schaffner said. "Instead of having a temperature requirement, the policy should only say that comfortable or warm water needs to be delivered. We are wasting energy to heat water to a level that is not necessary."

The FDA will discuss existing code regarding water temperature guidelines at a conference in 2018 and researchers urge changes to be made at that time.

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