A study protocol for an interrupted time series analysis and pre-post surveys to assess the effects a community-wide sanitation system on environmental contamination, infection risk, and well-being in the Alabama Black Belt

Rural sanitation deficits in the United States represent an important source of non-point source pollution and may present risks to public health. We propose an interrupted time series analysis to measure the effect of a town-wide sanitation expansion program 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. We will conduct a longitudinal baseline study including quantitative measurement of key enteric pathogens and fecal indicator bacteria adjacent to 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 concurrent comparison sites with existing appropriate sanitation as well as sites never receiving the intervention to monitor secular trends in pathogen releases during the study period. We will compare the concentration of culturable E. coli in the environment pre- and post-intervention using a time series regression analysis suitable for an interrupted time series. 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. 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 utilizes both molecular and culture-based environmental sampling with structured household and observational surveys to carefully assess the effects of a community-wide sanitation system on environmental contamination, infection risk, and well-being.To address potential confounding due to secular trends and/or weather-related events, we plan to include at least 10 comparison sites with existing improved sanitationinfrastructure and 10 sites with poor sanitation infrastructure not receiving the intervention during the study period.Bias will be reduced by defining enteric pathogen targets and the main statistical models prior to analysis.Although we will adjust for external trends such as temperature and rainfall, the design of an interrupted time series lacks a randomized control group, limiting the ability to fully isolate the intervention effect.Voluntary participation and required utility fees may lead to selection bias, and survey responses may be influenced by social desirability or courtesy bias. We aim to mitigate this through community engagement, confidentiality assurances, and validating survey responses with environmental testing.