(Inside Science TV) -- You know the drill. A little soap, water, scrub and then dry. It may be a dull routine, but hand-washing is important for good hygiene and health.
There are several hand-washing techniques out there, but 70 percent of Americans believe that using warm or hot water is the most effective way to kill germs. It turns out, however, that cooler water works just as well, and a new study says that using cooler water could be better for the environment.
Amanda Carrico, a psychologist at the University of Colorado Boulder said, "We do know that heat does kill bacteria but the temperature you'd have to get to in order to have that benefit is well beyond what the human skin can tolerate," said Amanda Carrico, a psychologist at the University of Colorado Boulder.
Warm or hot water can irritate the skin and using hot water can contribute to greenhouse gas emissions.
"To heat water you need energy, and any type of fossil-fuel-based energy, which is what the vast majority of energy in the U.S. is produced from, releases greenhouse gas emissions," said Carrico.
Running the hot water tap a few times a day may not seem like a huge use of energy. But, in the U.S. alone, there are more than eight hundred billion hand washes each year. The energy it takes to heat the water for all those washes accounts for about 6 million metric tons of greenhouse gas emissions per year in the U.S.
That amount is larger than the total yearly emissions of several smaller countries, according to Carrico.
Carrico recommends using cooler water, along with soap and a good scrub, to kill germs lurking on your hands.
And remember this tip: "Turn the water on and then sing happy birthday while you're washing your hands -- you can get to about 20 seconds or so," said Carrico.