Hand Washing: Hot Doesn’t Matter

Your mother was wrong. So, apparently, are U.S. Food and Drug Administration guidelines recommending that plumbing systems at food establishments and restaurants deliver water at 100 degrees Fahrenheit for handwashing. Rutgers University reports that researchers at the school put large amounts of harmless bacteria on the hands of 21 people multiple times over a six-month period, then asked them to wash their hands in 60-degree, 79-degree or 100-degree water temperatures using 0.5 ml, 1 ml or 2 ml volumes of soap. What did they find? Water temperature made no difference to the number of bacteria killed. “This study may have significant implications towards water energy, since using cold water saves more energy than warm or hot water,” said researcher Donald Schaffner, distinguished professor and extension specialist in food science. “Also we learned even washing for 10 seconds significantly removed bacteria from the hands.”

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