Equivalent reduction of Escherichia coli by rinsing hands with cold and warm water

Hand washing is considered an important public health intervention to reduce the burden of communicable diseases such as gastrointestinal and respiratory tract infections. Washbasins in public restrooms are often only equipped with cold water and it can be observed that people only rinse their hands briefly after using the toilet instead of washing them properly with soap. As there are no recommendations on the optimal water temperature for efficacy, we measured the efficacy of simple hand rinsing with cold (4°C) and warm (40°C) water for 10 and 20 seconds compared to the European Norm EN 1499 reference hand wash.

A Latin square design was used with five treatment groups and three participants per group. Hands were contaminated by immersion in an Escherichia coli suspension. Before and after the respective treatment fingertips were sampled to obtain pre- and post-values. Pre- and post-values were averaged separately for each volunteer and the arithmetic means of all individual lg reductions were calculated and compared using Wilcoxon's matched-pairs signed rank tests (one-sided, P<0.05). Post hoc test of differences between treatmets was done by Tukey's honest significant difference tests, P<0.05 was considered significant.

Rinsing hands for 10 seconds with cold (1.93 lg) or warm water (2.01 lg), and for 20 seconds with cold (2.23 lg) or warm water (2.39 lg) was significantly inferior to the 1 minute reference hand wash with sapo kalinus (2.68 lg), but there were no significant differences between the use of cold or warm water in the pairwise comparison for both times. However, the duration seems to have an effect on the bacterial reduction as the differences between the hand rinsing times were significant for both temperatures.

Rinsing hands with cold water was as effective as warm water. Its implementation in the community could save energy and resources without losing any efficacy.