Making Sanitation Count: Developing and Testing a Device for Assessing Latrine Use in Low-Income Settings

Distinguishing between latrine coverage and latrine usage is vital for assessing the health impact of sanitation. This paper by Clasen et al. (2012), published in Envrionmental Science and Technology, summarises the development and testing of an innovative device to assess actual latrine usage, the passive latrine use monitor (PLUM). The PLUM's ability to measure latrine activity was compared with structured observation. Each PLUM consisted of a passive infrared motion detector, microcontroller, data storage card, and batteries mounted in a small plastic housing that was positioned inside the latrine. During a field trial in Orissa, India, with approximately 115 households, the number of latrine events measured by the PLUMs was in good agreement with that measured by trained observers during five hours of structured observation per device per week. A significant finding was that the presence of a human observer was associated with a statistically significant increase in the number of latrine events, i.e., the users modified their behavior in response to the observer. Another advantage of the PLUM was the ability to measure activity continuously for an entire week. A shortcoming of the PLUM was the inability to separate latrine events that occurred in immediate succession, leading to possible undercounting during high-traffic periods. The PLUM is a promising technology that can provide detailed measures of latrine use to improve the understanding of sanitation behaviors and how to modify them and for assessing the intended health, livelihood, and environmental benefits of improved sanitation.