What is driving reliance on shared sanitation in urban informal settlements? Challenges and pathways for improvement

As urbanization accelerates in low- and middle-income countries, informal settlements have emerged as a persistent and expanding feature of urban landscapes, housing over a billion people globally. In these densely populated areas, reliance on shared sanitation facilities is prevalent, driven by spatial constraints, insecure land tenure, limited infrastructure, and socio-economic marginalization. While these facilities are often criticized for poor quality and safety concerns, they are essential in contexts where individual household toilets are infeasible. This critical review synthesizes evidence from 93 peer-reviewed studies and 9 grey literature sources across 22 countries, with a focus on Sub-Saharan Africa and South Asia. The analysis reveals that shared sanitation, while often classified as substandard, is an unavoidable interim solution in contexts where individual household facilities are impractical. Effective interventions, such as robust facility designs, participatory management models, and targeted behavior-change strategies, demonstrate significant potential to improve cleanliness, accessibility, and safety. However, systemic barriers—such as inadequate policies and regulations, fragmented land management systems, constrained socio-economic capacities, insufficient water and sanitation infrastructure, and weak governance typical of informal settlements—must be overcome to enhance the usability of shared sanitation facilities. The review underscores the necessity of integrating shared sanitation improvements within broader urban planning frameworks to achieve Sustainable Development Goals 6.2 and 11. By situating sanitation interventions within the socio-political realities of informal settlements, this study advances actionable insights for fostering resilient and inclusive urban sanitation systems in rapidly growing cities.