The surprising reason you should wash your hands in cool water

http://www.mnn.com/health/healthy-spaces/stories/the-surprising-reason-you-should-wash-your-hands-in-cool-water

Wed, Dec 18 2013

If you're like me, you probably learned from a young age that when you wash your hands, you need to turn the tap to hot, lather up, and rinse your hands. Ideally, you should be running your hands under water for at least 20 seconds (singing the alphabet song to yourself helps with timing this, FYI), to allow the surfactant action of the soap to help the water fully lift any dirt, grime and bacteria. Then you can dry off and pat yourself on the back: You did your part to prevent the spread of germs.

Only... about that hot water. It's estimated that around 800 billion hand washes occur in the United States, from sinks outside patient rooms in hospitals to your very own bathroom. The combined energy needed to heat the water for all those hand-washings is equivalent to the emissions of Barbados. Whoa.

But you need that hot water, right? Because hot water kills germs!

Wrong. Well, sort of wrong. In order to effectively kill most germs, hot water needs to be close to boiling — which is why instruments are boiled to sterilize them, and why dishwashers and other automated cleaning equipment gets to boiling or higher for washing. I don't know if you've tried washing your hands with boiling water lately, but it's not a pleasant, or, honestly, feasible, experience; after the recommended 20 seconds, your scalded hands would be throbbing with blisters.

So washing with hot water only works when the water is too hot to tolerate. Washing with warm water, on the other hand, can actually soften the upper layers of the skin, making you more vulnerable to germs. Washing with cool or cold water? May be just what the doctor (and the planet) ordered. The key components of hand-washing are the soap, friction (to lift debris from your skin), and a steady flow of water.

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Your individual hand-washing decisions might not seem like a big deal, but changing the way people wash their hands as a whole could generate huge energy savings across the country, which is great news for the planet, and your pocketbook.

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