Microbiological Evaluation of the Efficacy of Soapy Water to Clean Hands: A Randomized, Non-Inferiority Field Trial
Am. J. Trop. Med. Hyg., 91(2), 2014, pp. 415–423
doi:10.4269/ajtmh.13-0475
Copyright © 2014 by The American Society of Tropical Medicine and Hygiene
Microbiological Evaluation of the Efficacy of Soapy Water to Clean Hands:
A Randomized, Non-Inferiority Field Trial
Nuhu Amin,* Amy J. Pickering, Pavani K. Ram, Leanne Unicomb, Nusrat Najnin, Nusrat Homaira, Sania Ashraf,
Jaynal Abedin, M. Sirajul Islam, and Stephen P. Luby
International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh; Stanford University, Stanford, California;
University at Buffalo, Buffalo, New York; Centers for Disease Control and Prevention, Atlanta, Georgia
Abstract. We conducted a randomized, non-inferiority field trial in urban Dhaka, Bangladesh among mothers to
compare microbial efficacy of soapy water (30 g powdered detergent in 1.5 L water) with bar soap and water alone.
Fieldworkers collected hand rinse samples before and after the following washing regimens: scrubbing with soapy water
for 15 and 30 seconds; scrubbing with bar soap for 15 and 30 seconds; and scrubbing with water alone for 15 seconds. Soapy
water and bar soap removed thermotolerant coliforms similarly after washing for 15 seconds (mean log10 reduction =
0.7 colony-forming units [CFU], P < 0.001 for soapy water; mean log10 reduction = 0.6 CFU, P = 0.001 for bar soap).
Increasing scrubbing time to 30 seconds did not improve removal (P > 0.05). Scrubbing hands with water alone also reduced
thermotolerant coliforms (mean log10 reduction = 0.3 CFU, P = 0.046) but was less efficacious than scrubbing hands
with soapy water. Soapy water is an inexpensive and microbiologically effective cleansing agent to improve handwashing
among households with vulnerable children.
low-income rural16 and urban17 communities in Bangladesh18
for acceptability and feasibility. To make soapy water, 30 g
powdered detergent (Wheel, Unilever, Dhaka, Bangladesh)
is mixed in any 1.5 L container, such as a reused water/soda/
juice bottle. Preliminary qualitative research suggests that
soapy water is popular because of its low cost and ease of
preparation.16 In Bangladesh, a 30 g sachet of powder laundry
detergent costs US$0.03 compared with a common bar of soap
(Lux, Unilever, Dhaka, Bangladesh), which costs US$0.35.
The cost of freshly prepared soapy water is US$0.09 (detergent
US$0.03 + plastic bottle US$0.06), and the cost of refilling an
existing bottle is only US$0.03. Therefore, the lower cost
of soapy water compared with bar soap and the fact that it
can be kept in a reused plastic bottle may allow households
to ensure the availability of a cleansing agent for handwashing
at home. In addition, soapy water may be less likely to be
stolen than bar soap because of its low cost.18
However, there are no data on the microbial efficacy
of handwashing with soapy water in field settings. In a lowincome urban area in Dhaka, Bangladesh, we conducted a
randomized, non-inferiority field trial to compare the efficacy
of soapy water with the efficacy of bar soap and water alone
for removing thermotolerant coliforms and Clostridium
perfringens from hands. We also compared the efficacy of
soapy water and bar soap using two different hand scrubbing
times (15 and 30 seconds).
INTRODUCTION
Each year, approximately 600,000 children < 5 years old,
mostly from low-income countries, die of diarrhea.1 Handwashing with soap after defecation and handling feces and
before preparing and eating food can reduce the risk of diarrhea.2– 4 In both rural and urban communities of Bangladesh,
people rarely wash their hands with soap at recommended
times.5,6 In a study among rural Bangladeshi caregivers, fewer
than 1% used soap and water for handwashing before eating
and/or feeding a child, and only 33% of caregivers and 14%
of all household members were observed washing both hands
with soap after defecation.5
Barriers to washing hands with soap in low-income communities include the high cost of soap relative to household
income, the concern that soap left out at a common handwashing place could be stolen, and the concern that children
could play with or waste the bar soap.7–11 A study from 68 subdistricts of Bangladesh suggested that rural residents who live
in households with either water or soap at the handwashing
place were two times as likely to wash both hands with soap
after contact with feces as those residents who did not
have soap or water conveniently available.12 In addition,
Bangladeshi urban households from the wealthiest quintile
were more likely to have soap consistently at handwashing
stations (odds ratio [OR] = 1.9, 95% confidence interval [95%
CI] = 1.4–2.4) and wash their hands with soap at critical times
(adjusted OR [ORadj] = 1.4, 95% CI = 1.1–1.7).13 A number
of research studies from Bangladesh have shown that the cost
of soap is a barrier to its use.7–11 These findings suggest that
overcoming economic barriers to maintaining access to soap
in the home could increase handwashing frequency.
Soapy water is a mixture of powder detergent in water,
previously introduced as a handwashing agent in Kenya and
Peru in 2008.14,15 Soapy water is currently being piloted in
METHODS
A non-inferiority trial seeks to determine whether a new
treatment (soapy water) is not worse than a reference treatment (bar soap) by more than an acceptable amount.19
Selection and enrolment of respondents. We conducted this
study from July to September of 2011 in the Mirpur area of
urban Dhaka among mothers with at least one child < 5 years
old recruited from an ongoing observational study unrelated
to hand hygiene.20 The study area was selected for the
handwashing trial, because this area represents the other
low-income urban slums of Bangladesh with high levels
of environmental contamination. Using the Microsoft Excel
random number generator, one of the investigators (N.A.)
*Address correspondence to Nuhu Amin, Water Sanitation and
Hygiene Research Group, Centre for Communicable Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed
Tajuddin Ahmed Sarani, Mohakhali, Dhaka-1212, Bangladesh. E-mail:
415
416
AMIN AND OTHERS
randomly selected 84 mothers from a participant list of the
ongoing observational study. Using the same randomization
technique, N.A. assigned 28 mothers each (from 84 selected
mothers) to one of three different handwashing sequences
using the three different cleansing agents (Figure 1). All
selected mothers used three cleansing agents (soapy water
[30 g powdered detergent in 1.5 L water], bar soap [Lux], and
water alone; one agent per each visit).
Selection of hands and first scrubbing time. The investigator N.A. prepared 420 slips of paper, where hand selection
(right versus left) and duration of scrubbing (15 or 30 seconds)
were marked. The slips were placed within a envelope and
shuffled to assure that no one can identify which envelope
contains which hand and rubbing time. The fieldworker collected the re (...truncated)
