Cold Water as Effective as Hot Water for Handwashing and Killing Germs

Ray Weaver
June 3, 2017

"This is important because the biggest public health need is to increase handwashing or hand sanitizing by foodservice workers and the public before eating, preparing food and after using the restroom", says Jim Arbogast, study co-author and vice president of hygiene sciences and public health advancements for GOJO.

'This study may have significant implications towards water energy, since using cold water saves more energy than warm or hot water'.

Scientists say they've figuratively and literally thrown cold water on the theory that washing hands with hot water is more effective at killing germs. Each of the volunteers washed their hands 20 times over a 6-month period. The researchers put a non-virulent strain of E. coli on each person's hand prior to the cleansing to measure how the techniques worked.

However, the researchers accept their study is small and say more extensive work is needed to determine the best ways to remove harmful bacteria.

Results showed that there was no significant difference in the amount of bacteria removed by cold and hot water.

Still feel like you need hot water to have clean hands?

"Whether you use 60-degree Fahrenheit or 100-degree Fahrenheit temperature - or something in the middle - none of those temperatures had a significantly different effect than the other". "Now, what you shouldn't conclude from that is that this means you can just get away with not using any soap at all, or that you can get away with only using a very small amount of soap", says Professor Schaffner, who insists the findings do not support such a claim.

They asked 20 people to wash their hands 20 times each with water that was 15 degrees, 26 degrees or 38 degrees. "But for the time being, I don't see the recommendations changing but I'm hoping that this study will lead to more in-depth stories that can give us even stronger evidence that could lead us to changing our current recommendations".

"Instead of having a temperature requirement, the policy should only say that comfortable or warm water needs to be delivered", he said.

Scientists at Rutgers University-New Brunswick wanted to test if the popular assumptions on the benefits of using hot water, and the official guidelines on hot water use in the USA food industry, were true. It is important to wash one's hands for at least 10 seconds, though, and make sure lather from the soap that is used gets thoroughly washed off.

Also, using cold water comes with an energy-saving advantage, he adds.

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