Indicators for evaluating shared sanitation quality: a systematic review and recommendations for sanitation monitoring

The study addresses how to assess the quality of shared sanitation facilities used widely in informal settlements, where providing individual household toilets is often infeasible due to density, limited space, costs, and water needs. With an estimated 30% of the global population living in informal settlements, and hundreds of millions lacking basic sanitation—especially in sub-Saharan Africa and across Central and Southern Asia—shared facilities often replace open defecation and can be the most viable option in the near term. Despite their prevalence and potential health benefits over open defecation, measurement challenges persist: national and global monitoring struggle to distinguish high-quality shared sanitation from unacceptable options, and common surveys (DHS, MICS) collect limited detail on sharing, cleanliness, privacy, accessibility, and safety. The research question is to synthesize evidence on shared sanitation in informal settlements and identify practical, high-performing indicators that can reliably distinguish higher-quality shared facilities (conducive to better health and user needs) from unacceptable ones, to inform improved national and global monitoring and program design.

Prior studies have explored the prevalence and role of shared sanitation in improving access, user perceptions and preferences (e.g., affordability, cleanliness, 24-hour access, privacy, handwashing, lighting, menstrual health needs), and health outcomes. Evidence shows poorly maintained shared facilities can harbor pathogens and elevate diarrheal risk compared to private household toilets, though shared options offer clear benefits versus open defecation when adequately maintained. Despite interest, most monitoring systems and routine surveys lack granularity on critical attributes (number of households/people sharing, cleanliness, privacy, safety, accessibility). The JMP currently classifies shared sanitation as a limited service due to these monitoring constraints. Some literature suggests thresholds for acceptable sharing (e.g., ≤5 households or ≤30 people; SPHERE up to 4 households or 20 people in humanitarian settings), and emphasizes social organization, familiarity among users, and management practices. However, no comprehensive framework existed to prioritize which shared sanitation dimensions most critically influence quality and health outcomes, motivating this systematic review to develop and recommend indicator sets.

The review followed PRISMA 2020 guidelines and was prospectively registered on PROSPERO (CRD42023431460). Seven databases (PubMed, Scopus, Embase, Cochrane Central, Global Health, Environment Complete, VHL Regional Portal) were searched for studies published up to June 30, 2023. Grey literature was sought via Google Scholar and 19 organizational websites. A PubMed search strategy on shared sanitation and informal settlements (with synonyms/alternative spellings) was adapted for other databases; reference lists of eligible full texts were hand-searched. Inclusion criteria: studies on sanitation facilities shared by more than one household; public or communal toilets; focused on informal settlements; English-language; published before June 30, 2023. Exclusions: non-household/institutional sanitation (schools, markets, transport hubs, healthcare). No geographic income restrictions. Screening was managed in Covidence: duplicates removed; two reviewers independently screened titles/abstracts and full texts, with a third reviewer adjudicating 10% of full texts and conflicts. Data extraction used a piloted form capturing study metadata; user profiles; cleanliness, privacy, safety, costs, management; indicators for evaluation; and health outcomes, guided by Human Rights to Water and Sanitation criteria (availability, quality/safety, physical accessibility, affordability, acceptability). Five reviewers extracted data; qualitative tags were exported and grouped by number of households sharing and country. Risk of bias and quality were assessed using adapted WASH tools for observational studies and ROBIS for non-observational studies. A 10-item checklist (aims, context, design clarity, data collection, analysis quality, rigor, interpretation, limitations, conclusions, strength of evidence) scored 0/0.5/1 per item to derive overall ratings. Indicator selection used an inductive approach from published studies and applied seven criteria for high-performing indicators: accepted practice/history of use; measurability; data availability; applicability across settings; burden of data collection; clarity of focus/meaning; and independence/additive value. Indicators were rated high (≥6 criteria), medium (4–5), or low (1–3). Funding sources had no role in study design, conduct, analysis, interpretation, or reporting.

• Search and inclusion: 4,741 peer-reviewed and 2,788 grey literature records identified; 1,953 unique articles screened; 325 full texts assessed; 248 studies included. Studies spanned 23 countries (mostly Sub-Saharan Africa, n=114; Southern Asia, n=64); India (n=41), Kenya (n=28), Uganda (n=21) were most represented. All studies were urban informal settlements (179 settlements covered). Study designs: cross-sectional (133), case studies (45), reports (15), reviews (10), expert opinions (10), experimental (9), case-control (8), cohort (8), policy analyses (7), modeling (3). • Quality assessment: Mean quality score ~85% (≈11/13). Rigor of methods averaged 72%; only 74% adequately described study limitations. Frequent issues: inadequate description of analysis methods, lack of data collection validation and verification. • Long list and prioritization: Many candidate indicators across domains were appraised against seven selection criteria; six indicators scoring ≥80% evidence quality and high/medium on selection criteria were prioritized: number of households/people sharing; facility location; facility cleanliness; accessibility; safety and security; privacy. • Number of households/people sharing: Reported in 52 studies (~21%). Average 16 households per facility; average household size ~5. Heavier sharing (>10 households) was less common. Evidence suggests an inverse relationship between number sharing and quality/cleanliness; large user groups complicate management and consensus. Suggested thresholds in literature: ≤5 households or ≤30 people (SPHERE: ≤4 households or ≤20 people in humanitarian settings), though conclusive scientific cutoff is lacking. Management strategies (gendered units, assigned units, cleaning schedules, pooled funding, keys) can mitigate challenges; familiarity/kinship and landlord-tenant dynamics influence cleanliness and functionality. Health associations: heavily shared toilets (>18 people) associated with waterborne illness (OR 1.18, 95% CI 1.06–1.31) and diarrhea (OR 1.33, 95% CI 1.17–1.53). Dose-response evidence is mixed across studies. • Facility location: In-compound facilities are preferred over off-compound public toilets; they increase convenience, reduce time and perceived risk—especially at night—and are often cost-free at point of use for tenants. Empirical examples highlight long distances to community toilets in some settings (e.g., 150 m average; up to 20 minutes’ walk; 1–1.5 km for some communities), contributing to safety concerns and nonuse. Proximity is linked to positive wellbeing and perceived safety, though more empirical links to assault risk are needed. • Facility cleanliness: Cleanliness problems were reported in 90 studies (36%). Barriers include lack of cleaning schedules/enforcement, absent cleaning materials/water, poor ventilation, lack of locks, and lack of monitoring; reported AORs for barriers included: low income < $55.6/month (AOR 1.80; 95% CI 1.20–3.10), lack of privacy (AOR 2.95; 1.60–5.43), no locking latch (AOR 4.60; 2.43–8.79), inadequate ventilation (AOR 4.88; 2.44–9.63), no regular monitoring (AOR 2.86; 1.32–6.21), insufficient water (AOR 4.91; 1.07–9.48). Microbiological assessments detected diverse and potentially pathogenic bacteria on contact surfaces. Physical features (tiled/plastered floors) and management (designated caretaker, restricted access, cleaning materials) support cleanliness. Indicators of poor cleanliness include visible feces, odor, flies/insects, improper menstrual waste disposal, drainage/clogging issues, infrequent cleaning, lack of equipment, and absent functional handwashing with soap. • Accessibility: Defined by proximity, hours of operation, queue time, and inclusive design for disabled persons, elderly, and children. Barriers include closures at night, long distances/waits, slippery conditions in rain, crowding. Lack of accessible facilities is linked to open defecation, especially at night among women/girls. Indicators include toilets near premises, inclusive features for people with disabilities, and availability when needed. • Privacy: Adequate privacy involves well-fitting lockable doors, solid walls/roofs without cracks/holes, and, where feasible, gender-segregated units. Toilets closer to homes can improve privacy relative to centrally located public facilities. Some evidence shows shared facilities may more often have lockable doors than non-shared in certain contexts. • Safety and security: Women and girls face increased risks of harassment and sexual violence when toilets are distant or poorly lit/secured, contributing to psychosocial stress, fluid restriction, constipation, and unsafe coping behaviors. Risk hotspots include peripheral or isolated locations. Mitigations include proper lighting inside/outside cubicles, lockable doors, proximity to homes, and presence of a 24-hour caretaker. • Proposed reclassification and tool: A decision-tree indicator matrix classifies shared facilities into improved shared, basic shared, or unimproved shared, based on technology type, number of households/people sharing (≤5 households or ≤30 people for improved shared), in-compound location, accessibility for all users, lockability/safety, and cleanliness responsibility. Unimproved shared includes technologies that do not ensure hygienic separation (e.g., pit without slab, hanging, bucket latrines) even if shared. • Recommendations: Incorporate prioritized indicators into primary data collection and routine national/global monitoring to distinguish higher-quality shared sanitation and guide investment and program improvement in informal settlements.

The review synthesizes dispersed evidence to identify practical indicators that capture the quality dimensions of shared sanitation most associated with user preferences and potential health impacts. By prioritizing six indicators—number sharing, location, cleanliness, accessibility, safety/security, and privacy—the study addresses a key monitoring gap in distinguishing high-quality from unacceptable shared facilities. Findings suggest quality declines with increasing user numbers absent strong management, while proximity, reliable access (including at night), robust physical security and privacy features, and active cleanliness systems are central to acceptable shared sanitation. The decision-tree and proposed reclassification provide a pragmatic framework for governments and monitoring agencies to refine the categorization of shared sanitation beyond a blanket “limited” designation, recognizing contexts where high-quality shared options are the most feasible and beneficial compared to open defecation. The discussion emphasizes that strict numerical thresholds may be less important than effective management, user familiarity and social organization, and supportive design and oversight; however, indicative thresholds can guide planning. Integration of these indicators in surveys and program monitoring can improve comparability, resource targeting, and health-oriented outcomes while advancing equity for women, children, the elderly, and people with disabilities.

This systematic review consolidates evidence on shared sanitation in informal settlements and proposes a prioritized, feasible set of indicators—number of households/people sharing, facility location, cleanliness, accessibility, safety/security, and privacy—along with a decision-tree tool to classify facilities as improved shared, basic shared, or unimproved shared. Adoption of these indicators in primary data collection and routine national and global monitoring can better differentiate quality levels, guide investments, incentivize improved service provision, and support safer, more acceptable sanitation where individual household toilets are impractical. Future research should: (1) strengthen empirical links between specific indicators and health outcomes (including dose-response for sharing levels); (2) refine acceptable thresholds for sharing in diverse contexts (including humanitarian settings); (3) evaluate the role of external support to complement internal management for shared facilities; (4) study interventions that enhance safety and reduce gender-based violence risks; and (5) improve standardized measurement of privacy, accessibility, and cleanliness across settings.

Evidence synthesis is constrained by heterogeneity across studies, predominance of cross-sectional and descriptive designs, and limited consistent reporting on key variables (e.g., exact numbers sharing, gender/age ratios). Many national surveys lack detailed measures on cleanliness, privacy, accessibility, and safety, limiting comparability. Only English-language studies up to June 30, 2023 were included. The quality assessment highlighted methodological limitations in the literature, including inadequate description of analysis methods, limited validation and verification of data collection, and incomplete reporting of study limitations. Thresholds for acceptable sharing remain indicative rather than conclusive, and causal inferences linking specific indicators to health outcomes are limited.