In our never-ending quest to lead greener lifestyles, here’s a simple modification to something you do multiple times every day: washing your hands. While most of us have been taught to wash our hands with hot water, research out of Vanderbilt University suggests that water of any temperature will do the trick.
For this reason, the ecologically minded professors are advocating that people make the switch to cold or neutral temperature hand washing. In addition to wasting water while waiting for the running faucet to heat up, the energy used to heat the water contributes to greenhouse gas emissions. A single wash of the hands may be negligible, but when you multiply that by the eight billion times per year that Americans engage in this activity, it adds up to a startling 6 million metric tons of carbon output. (For context, that’s equivalent to Barbados’s total emissions in a single year.)
“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,” wrote professor Amanda Carrico in the published study. “It is true that heat kills bacteria; however, the level of the heat required to neutralize pathogens is beyond what is considered safe for prolonged human contact.”
We know that hot water kills germs; after all, the best way to sterilize water is to boil it. However, you wouldn’t wash your hands in boiling water. In order for the water temperature to be hot enough to kill any bacteria, it would injure your hands. It’s the soap, not the temperature, that’s doing the germ killing while you’re standing at the sink. Since the research shows that warm water is no more beneficial than cooler water in this case, what’s the point in wasting energy on heating the water?
If anything, a cooler temperature might actually be more beneficial, according to the Vanderbilt researchers. Hotter water “can cause skin irritation, which can lead to more bacterial colonization, not less.”
To be clear, no one’s arguing that you should stop washing your hands to help the environment. Washing your hands is one of the easiest and most effective ways to stay healthy, yet many Americans skip the ritual even after going to the bathroom.
Still, if enough Americans made the switch to a comfortably cooler water temperature and eliminated the need to fire up the water heaters, the reduced level of carbon emissions would buy us that much more time before the worst of climate change strikes the planet.