Controlled, before-and-after analysis and pre-post surveys to assess the effects of a community-wide sanitation system on environmental contamination, infection risk and well-being in Alabama's Black Belt: study protocol.

INTRODUCTION: Rural sanitation deficits in the USA represent an important source of non-point source pollution and may present risks to public health. We propose a controlled, before-and-after (CBA) study using a difference-in-differences analysis to measure the effect of a town-wide sanitation expansion programme on the release of pathogens to the environment. This work is expected to yield valuable insight into the potential for rural sanitation improvements to reduce pathogen releases and support public health and well-being.

METHODS: We will conduct a CBA study including quantitative measurement of key enteric pathogens and faecal indicator bacteria adjacent to 30 households lacking adequate sanitation. As households connect to a new sewerage system serving the entire community, longitudinal household sampling will continue until crossover is complete. We will include 10 concurrent control sites with existing appropriate sanitation as well as 10 control sites never receiving the intervention to monitor secular trends in pathogen releases during the study period.

ANALYSIS: We will compare the concentration of culturable Escherichia coli in the environment preintervention and postintervention between intervention and control groups. We will use the preintervention values of culturable E. coli in the environment to adjust the effect size for differences between the groups at baseline. We will couple pathogen measurements with quantitative microbial risk assessment to estimate the potential effect of the intervention on infection risks via key exposure pathways. A linked pre-post survey will focus on self-reported quality of life measures among households connecting to the system.

ETHICS AND DISSEMINATION: Informed consent will be obtained prior to data collection, with participants informed of study details and risks. Participation is completely voluntary, and identifiable data will be securely and separately stored from all other data. Each household will be offered a summary of their site-specific data. Deidentified results will be shared with the community in a public forum and published in peer-reviewed journals. This study was approved by the Institutional Review Board for Human Subjects Research (IRB) at the University of North Carolina at Chapel Hill (IRB #24-0665).