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Washing Your Hands in Hot Water Wastes Energy–And Doesn’t Make Them Any Cleaner Than Cold

If Americans turned down the heat when washing their hands they could save 6 million metric tons of CO2 every year

When you go to wash your hands do you use cold or hot water? Most people prefer hot—a habit that's hurting the planet. According to a recent study from Vanderbilt University, if Americans turned down the heat when washing their hands they could save 6 million metric tons of carbon dioxide every year. That's the same amount of CO2 that the United States lead industry puts out in the same period. It's about how much CO2 the entire country of Barbados emits.

Amanda Carrico, the lead author on the paper, surveyed 510 people about their hand washing techniques and then estimated how much energy they were using. Most people—64 percent in the study—prefer to use hot water when washing. When you multiply that by the eight billion times Americans wash their hands each year, and how much energy it takes to heat that water, you wind up with a surprising amount of energy—0.1 percent of the total annual emissions of the United States.

People think that using hot water to wash their hands is more hygienic, but Carrico says that's not really true. “Although the perception that hot water is more hygienic is based in some factual evidence ... there are few, if any, hygienic benefits of using warm or hot water to wash one’s hands," she writes. The amount of heat required to kill bacteria is far higher than what your hands can withstand. So next time you're washing, turn down the heat.

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About Rose Eveleth
Rose Eveleth

Rose Eveleth is a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.

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