Serial Measurements of Soap Weights and Soap Availability to Describe Handwashing Behavior

Available measures of handwashing are prone to bias. We tested the feasibility and reliability of weighing soap at repeated visits and subtracting the measured weight from the prior weight to assess daily per capita soap consumption in a low-income community in Dhaka, Bangladesh. Fieldworkers approached 220 households twice weekly over 2 months. They interviewed participants, weighed soap, and assessed hand cleanliness and the presence of a handwashing station. Respondents used bar soap (91% [201]) and laundry detergent cakes (39% [85]) for handwashing as well as for bathing and laundry. Ninety-eight percent of households had bar soap present on at least one visit, although only 50% had bar soap at every visit during the 2-month period. Fieldworkers observed a soap fragment on the wall near the latrine in 27% (470) of visits. Households consumed a mean 1.5 g of bar soap and 3.2 g detergent cake per person per day. Daily per capita soap consumption was similar in households visited by fieldworkers after different intervals (2, 3, 4, or 5 days). Soap consumption was not associated with household wealth, education of the household head, the presence of a handwashing station, the presence of water or soap at a handwashing station, or palm inspections of the mother or child. Soap weight measurements were an objective, reliable measure of soap consumption that provided different information from other handwashing indicators. The frequent use of a soap product for purposes other than handwashing complicates using soap consumption as a handwashing measure.