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    Asia Global Energy News: Study Says, Washing Hands in Hot Water Wastes Energy

    4 years agoReply
    It doesn’t kill germs better than cooler water, but turning tap temperatures high, the U.S. burns carbon equal to the emissions of Barbados.

    “People typically wash their hands seven times a day in the United States, but they do it at a far higher temperature than is necessary to kill germs, a new study says. The energy waste is equivalent to the fuel use of a small country.” – National Geographic

    It's cold and flu season, when many people are concerned about avoiding germs. But forget what you think you know about hand washing, say researchers at Vanderbilt University. Chances are good that how you clean up is not helping you stay healthy; it is helping to make the planet sick. Amanda R. Carrico, a research assistant professor at the Vanderbilt Institute for Energy and Environment in Tennessee, told National Geographic that hand washing is often "a case where people act in ways that they think are in their best interest, but they in fact have inaccurate beliefs or outdated perceptions."

    She explained that boiling water, 212°F (99.98°C), is sometimes used to kill germs-for example, to disinfect drinking water that might be contaminated with pathogens. But "hot" water for hand washing is generally within 104°F to 131°F (40°C to 55°C.) At the high end of that range, heat could kill some pathogens, but the sustained contact that would be required would scald the skin. Carrico said that after a review of the scientific literature, her team found "no evidence that using hot water that a person could stand would have any benefit in killing bacteria." Even water as cold as 40°F (4.4°C) appeared to reduce bacteria as well as hotter water, if hands were scrubbed, rinsed, and dried properly.

    In fact, she noted that hot water can often have an adverse effect on hygiene. "Warmer water can irritate the skin and affect the protective layer on the outside, which can cause it to be less resistant to bacteria," said Carrico. Using hot water to wash hands is therefore unnecessary, as well as wasteful, Carrico said, particularly when it comes to the environment. According to her research, people use warm or hot water 64 percent of the time when they wash their hands. Using that number, Carrico's team calculated a significant impact on the planet. (See related “Quiz: What You Don’t Know About Climate Change Science.”)

    That's roughly equal to the emissions of two coal-fired power plants, or 1,250,000 passenger vehicles, over the course of a year. It's higher than the greenhouse gas emissions of small countries like El Salvador or Armenia, and is about equivalent to the emissions of Barbados. If all U.S. citizens washed their hands in cooler water, it would be like eliminating the energy-related carbon emissions of 299,700 U.S. homes, or the total annual emissions from the U.S. zinc or lead industries. (See related, "Six Stealthy Energy Hogs: Are They Lurking In Your Home?")

    Gauging Hand Washing

    Carrico said she decided to look at hand washing after searching for easy ways to reduce climate change emissions. "Sometimes simply educating people can go a long way toward changing behavior and reducing emissions," she said.

    By zeroing in on hot water, she focused on an important source of emissions and potential waste. After heating and cooling, water heating is typically the largest energy user in the home because it is necessary for so many domestic activities, says the American Council for an Energy-Efficient Economy (ACEEE). In both the United States and European Union, hot water heating accounts for 15 percent of home energy use. But homeowners often keep their hot water heaters turned up to a temperature far higher than is necessary for most household tasks, which efficiency experts says is no more than 120°F (48.9° C.) Every 10°F (5.6° C) reduction in water temperature will generally save 3 to 5 percent on water heating costs, says ACEEE. (How much can you save by switching lighting at home? Try the Light Bulb Savings Calculator.)

    The researchers found that close to 70 percent of respondents said they believe that using hot water is more effective than warm, room temperature, or cold water, despite a lack of evidence backing that up, said Carrico. Her study noted research that showed a "strong cognitive connection" between water temperature and hygiene in both the United States and Western Europe, compared to other countries, like Japan, where hot water is associated more with comfort than with health. (See related, "Four Ways to Look at Global Carbon Footprints.") The researchers published their results in the July 2013 issue of International Journal of Consumer Studies. They recommended washing with water that is at a "comfortable" temperature, which they noted may be warmer in cold months and cooler in hot ones.

    Complete story: http://news.nationalgeographic.com/news/..
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