Cold water has been thrown on the traditional belief that hot water facilitates effective handwashing. A latest study by researchers at Rutgers University, New Jersey, US, concludes that washing hands in cold water is just as effective in killing harmful bacteria. Instead of focusing on water temperature, researchers conclude that bacteria, even Escherichia coli (E.coli), can be removed from contaminated hands as long as proper handwashing technique and sanitary products are used. If people scrub their hands with soap for at least 10 seconds, then it does not matter whether the water is cold, according to the study that has appeared in the June issue of the Journal of Food Protection.
It may be recalled that the US Food and Drug Administration (FDA) recommends a minimum handwashing water temperature of at least 38C to kill harmful bacteria. Prof Donald Schaffner and his team of researchers say their study could help cut down wasted energy used for heating water for handwashing in food establishments where the FDA strictly enforces the regulation. Prof Schaffner is a specialist in food science at the university.
There are many techniques claiming to be the most effective handwashing practice to eliminate harmful bacteria from our hands, but some open up contradictions while others lack scientific evidence to prove its legitimacy. To separate fact from fiction, Professor Schaffner and his colleagues challenged the popular assumptions and official FDA recommendations about handwashing through a series of tests done over a period of six months.
A group of 20 individuals were asked to participate in the handwashing experiments wherein the research team contaminated the participants’ hands with harmless bacteria (nonpathogenic E. coli) prior to washing their hands. The participants were then asked to wash their hands multiple times in water temperatures ranging from 15C to 38C and soap volume ranging from 0.5ml to 2ml. Results showed that there was no significant difference in the amount of bacteria removed by cold and hot water. The only difference was in the energy that was used for heating up the water. Other handwashing techniques the team challenged involved beliefs about washing time, product formulation, and amount of soap used.
According to Prof Schaffner, their results showed that even the amount of soap used did not show significant results, and the bland soap killed as much bacteria as the tested antimicrobial soap with 1% chloroxylenol formulation. The only other improvement in bacteria reduction came from a 20-second lather time using bland soap compared to the basic 5-second wash.
Using the results of their study, the team recommends that FDA should consider a policy change when it comes to handwashing guidelines. Understanding what behaviours and human factors most influence hand washing may help researchers find techniques to optimise the effectiveness of handwashing. Hand-washing saves lives. Proper technique can cut cold and flu risk, prevent the spread of foodborne illnesses and other infections.
