Washing hands with cool water kills as many germs as hot


Most of us are taught that washing hands with hot water and soap is key to keeping germs at bay.

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However, researchers from Rutgers University have now reported that cool water removes the same amount of harmful bacteria as hot.

In a new study, academics put high levels of a harmless bacteria on the hands of 21 participants multiple times over a six-month period before they were asked to wash their hands in 60-degree (15 degrees Celsius), 79-degree (26 degrees Celsius) or 100-degree (37 degrees Celsius) water temperatures using 0.5ml, 1ml or 2ml volumes of soap.

When it came to the results, Professor Donald Schaffner stated that the temperature of the water used "didn't matter".

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

The findings also indicated that there is no difference in germ killing when it came to the amount of soap used, but study co-author Jim Arbogast wants to do further investigation into exactly how much and what type of soap is needed to remove harmful microbes from hands.

"This is important because the biggest public health need is to increase hand washing or hand sanitising by foodservice workers and the public before eating, preparing food and after using the restroom," he said.

At present, U.S. Food and Drug Administration guidelines recommend that plumbing systems at food establishments and restaurants deliver water at 100 degrees Fahrenheit (37 degrees Celsius) for hand washing.

Schaffner explained that the issue of water temperature has been debated for a number of years, but he would like to see a revision of policy guidelines.

"I think this study indicates that there should be a policy change," he 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 full study has been published in the Journal of Food Protection.

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