In urban areas of sub-Saharan Africa, an estimated 146.8 million people rely on “limited” sanitation services, toilet facilities which, as classified by the Sustainable Development Goal (SDG) target 6.2, are improved but shared with other households ¹. Reliance on shared sanitation is associated with increased risk of diarrheal illness and enteric infection ^2–4. Throughout sub-Saharan Africa, both public and residentially shared toilets in low-income neighborhoods commonly exhibit poor cleanliness, a major detriment to the well-being and dignity of users ^5–8. Despite these challenges, high density and limited municipal and housing infrastructure make private (unshared) household sanitation infeasible in many urban areas ⁹. In such cases, the World Health Organization (WHO) recommends the promotion of shared sanitation that meets basic standards, including cleanliness/hygiene, as an incremental improvement ¹⁰.

Initiatives to promote safe and acceptable shared sanitation – and to identify improvements for unsafe and unacceptable shared sanitation – must distinguish between good versus poor quality services ¹¹. This entails rigorous characterization of key service aspects, such as cleanliness of facilities or effectiveness of cleaning practices ^9,12. Most commonly-used cleanliness assessment approaches employ observational criteria, including the presence or absence of visible fecal, urine, or solid waste, noticeable odor, visible signs of pests, or alternatively assigning a Likert scale rating of cleanliness ^13–17. These criteria, while critical to service quality and social acceptability, have limited ability to characterize surface contamination relevant to disease transmission. Additionally, these criteria focus on areas typically cleaned when visibly soiled or odorous (e.g., floor, drop hole, or toilet bowl/seat) and neglect surfaces within toilet compartments frequently touched before or after toilet use (e.g., door handles, flush handles, sink taps) that represent significant pathways for the transfer of enteric and respiratory pathogens ¹⁸, of particular concern during the COVID-19 pandemic ¹⁹. Previous studies assessing surface contamination in shared toilets in sub-Saharan Africa have sampled and cultured for E. coli ^20,21; however, these microbiological methods require laboratory capacity and training, which may present significant barriers in low-resource settings.

Measurement of organic surface contamination via bioluminescence of Adenosine Triphosphate (ATP) is a long-established method for hygiene monitoring in healthcare facilities for prevention of healthcare-acquired infections ²² and in the food industry for prevention of foodborne disease ²³. Studies in healthcare facilities have included sampling from toilets^24,25, as have studies in other notable settings, such as schools²⁶, libraries²⁷, and long-term care facilities²⁸. ATP testing has also been used to assess cleaning and disinfection in South Africa in a low-resource pediatric hospital ^29,30. Reducing ATP levels is a demonstrated proxy for removal of pathogens and microbial contamination from surfaces ³¹ even as, in addition to microorganisms, ATP measurements capture non-living material (e.g., skin or plant debris) and so do not correspond directly to measures of microbial contamination ³². ATP-based cleanliness testing provides near instantaneous results with minimal equipment, comprising surface swabs, positive controls, refrigerated storage, and a luminometer to read samples in the field ³³. Thus, it could potentially provide a comparatively more objective (versus observation alone), field-feasible measure of surface contamination and/or cleaning and disinfection practices for shared toilets in low-resource settings.

While ATP based testing has been used to assess cleanliness in toilets, this application has generally not been the primary focus and studies including toilets have been entirely limited to high-resource settings. The applicability of ATP testing is unknown for low-resource shared toilets in sub-Saharan Africa, which serve as main sanitation access points for communities and differ substantially from public toilets in high-income countries in design, surface materials, and usage patterns. We piloted this methodology to evaluate surface contamination and the efficacy of varying cleaning and disinfection procedures within urban neighborhoods of Kisumu, Kenya, with high usage of shared sanitation ³⁴. Results will provide insights into use of ATP testing as a practical surface cleanliness evaluation tool, as well as performance of cleaning and disinfection procedures themselves in removing surface contamination, for programs that aim to reduce disease transmission risk in low-resource shared sanitation facilities.

Recommended cleaning and disinfection procedures for high-touch surfaces (interior door handles) in publicly and residentially shared toilets yielded consistent and substantial reductions in organic surface contamination assessed via ATP testing. However, results were mixed for standard practice cleanings, with only minimal or no reductions when disinfection did not accompany cleaning. Additionally, we observed notable discordance between levels of organic surface contamination on high-touch surfaces and observation-based metrics of surface and overall toilet cleanliness. Taken together, these findings suggest ATP testing may be a useful complement to traditional observation-based WASH assessment metrics for its ability to characterize recent cleaning and disinfection. However, even after use of rigorous cleaning and disinfection procedures, most surfaces did not meet the manufacturer-recommended pass/fail threshold, suggesting a different, yet-to-be-determined benchmark may be appropriate for low-resource shared toilets. Background levels of organic surface contamination were higher in public toilets than shared residential toilets, suggesting toilets near commercial activities should be prioritized for cleaning and disinfection interventions and may also yield the most detectable pre- and post-disinfection differences.

Microbiological contamination of surfaces in shared toilets in sub-Saharan Africa has been characterized previously, largely via testing for E. coli in studies in Mozambique, Tanzania, and Ghana ^12,20,21, as well as via recovery of pathogens from surfaces, such as SARS-COV-2 ⁴⁸. However, to our knowledge, this study is the first to present data on ATP testing for this setting. Such rapid environmental assessment tools that require relatively less technical training are typically easier to use than laboratory-based culture methods ⁴⁹. ATP testing has the capacity to detect surface contamination of any biological origin, both living and non-living. In shared toilets, this may include bacterial contamination that largely traces back to human contact ⁵⁰ but also may include cell material from other organisms, such as human skin itself or material from plants ³², all of which are relevant to surface cleanliness. This analysis also presents evidence assessing cleaning and disinfection procedures already in practice at toilet sites that offer an important comparison to cleaning and disinfection procedures recommended in the literature ^36,37.

Observed reductions in surface contamination align with findings presented in a systematic review of several studies of ATP testing in healthcare facilities reporting lower surface contamination after disinfection despite a wide variety of surfaces, study sites, cleaning procedures, testing equipment, and cleanliness thresholds used throughout these studies ³⁹. In a study in a Brazilian hospital, toilet door handles were one of few tested surfaces where cleaning and disinfection with a quaternary ammonium-based disinfectant resulted in reduced surface contamination, measuring at a median 137 RLU/100cm² post-disinfection compared to 358/100cm² RLU pre-disinfection ²⁴. Conversely, in the Researching Effective Approaches to Cleaning in Hospitals (REACH) trial, ATP-based cleanliness improvements were observed for patient rooms but not bathroom surfaces; however, this study assessed the relative impact of a cleaning intervention on post-cleaning surfaces exclusively, with a high proportion of bathroom surface cleanings that met the cleanliness threshold before the training intervention took place ²⁵.

While no widely-recognized, non-healthcare protocols exist for cleaning and disinfecting in shared toilets, recommendations for low-resource healthcare settings – either cleaning then use of 0.5% chlorine solution given biohazardous spillages or excessive organic matter or cleaning then use of 0.1% chlorine solution to address potential pathogenic contamination on most non-excessively dirty surfaces ⁵¹ – may be appropriate for shared toilets in managing contamination due to soiling or deposition from hands. Our observation of reduced surface contamination following these procedures, but less consistent reductions when disinfecting using lower chlorine concentrations (~0.02%), supports the relatively better performance of chlorine solutions in these ranges. Additionally, little-to-no impact on surface contamination for observed standard practices supports recommendations that a two-stage process – cleaning then application of an appropriate disinfectant – is required for effectiveness ⁵¹. The underlying mechanism may involve a combination of additional wiping ⁵² and degradation of ATP. Interrogation of the isolated contribution of each step may be informative, although disinfection alone should not substitute the cleaning step given its reduced efficacy on dirty surfaces ⁵¹. Disinfectants applied directly to testing swabs may also interfere with ATP testing reactions ⁵³; however, for recommended procedures in this study, disinfectants were wiped off surfaces before ATP swabbing using a clean paper towel. Of importance to note, ATP testing alone cannot determine the efficacy of disinfection to inactivate microorganisms; indeed, 18% of HT surface swabs in this study included areas of bare wood that are porous and for which complete disinfection may not be achieved ⁵². Where possible, high-touch surfaces should be made from non-porous materials to allow for effective cleaning and disinfection ⁵¹; otherwise, effective sanitizing products should be used if controlling contamination on porous high-touch surfaces is needed.

The high discordance between visually assessed toilet cleanliness and ATP-based measures is consistent with a review presenting findings from several studies in healthcare settings that compared visual assessment to ATP-based cleanliness testing, as well as to other cleanliness assessment methods (involving removal of fluorescent markers or culture of aerobic colony counts) ²². Unreliability of visual cleanliness assessment has also been noted in studies involving bathroom surfaces in university libraries and hotels ^27,54. Therefore, the previously-described metrics of toilet cleanliness, which are broadly used and rely primarily on visual assessment ^13–16, may only be sufficient for identifying highly soiled surfaces in toilets. Even so, observation-based cleanliness monitoring, which makes use of these common metrics, provides essential feedback to inform effective strategies to improve overall toilet cleanliness ^55,56 and targets aspects of toilet cleanliness imperative to user acceptability, dignity, and alleviation of sanitation-related stress ^11,8. While more sensitive at characterizing surface contamination, routine ATP testing involves a cost burden that, even if comparatively lower than some microbiological methods, would be unrealistic given the already considerable operation costs of public toilets ⁵⁷ or for the limited pooled financial contributions used for residential toilet maintenance ^55,58. Therefore, routine ATP-based cleanliness monitoring of shared toilets might only be prioritized for specialized contexts, such as in areas of high transmission risk in disease outbreak settings ⁵⁹. More broadly, ATP-based cleanliness assessments may be well-suited to evaluate whether staff trained on cleaning interventions are able to practice them effectively ²⁵, aid in the development of or training on effective cleaning procedures by identifying surfaces with persistent contamination ⁴², or assess the validity of widely-deployable cleaning practice monitoring tools or approaches (e.g. cleaning protocol checklists) that may be candidates for inclusion in standards or criteria of quality shared sanitation services.

Even after carrying out procedures recommended for effective surface cleaning and disinfection, most post-disinfection levels recorded in this study fell above the manufacturer’s recommended pass/fail threshold of <250 RLU/100cm², suggesting it may not be achievable for low-resource shared toilets. ATP measurements can vary by surface material type and age, which affect ease of cleaning and surface topography ³³; shared toilets in low-resource settings are often constructed from a variety of low-cost materials, which may age before replacement due to barriers to regular maintenance ¹³. Furthermore, previous research has identified the importance of using benchmarks specified for a given setting ²⁷. The pass/caution/fail limits reported in this study may provide practical initial values for comparison by other cleanliness evaluations of high-touch surfaces in low-resource shared toilets. The same methodology may also be used to set limits for additional surfaces and cleaning protocols ⁴⁴. However, it is crucial that threshold values represent meaningful reduction in disease transmission risk. To this end, standardized healthcare ATP cleanliness benchmarks have been established through assessing the removal of pathogens of concern for healthcare-acquired infections, such as Staphylococcus aureus ³¹. In shared toilets, disease transmission concerns include a wide variety of enteric and respiratory pathogens – including norovirus, Salmonella, Hepatitis A, Shigella, SARS-CoV-2, and others – all of which have been associated with public toilets via outbreak investigation or recovery from a variety of surfaces, including toilet seats, flush handles, sink taps, and door handles ¹⁸. Consequently, evaluating ATP testing levels alongside markers for fecal and potential enteric pathogen contamination on surfaces would strengthen the validity of cleanliness monitoring benchmarks in shared toilets ^60,61. Without such evidence, comparison of pre- and post-cleaning ATP levels may be more meaningful than absolute ATP levels, because it most clearly demonstrates relative cleanliness improvements for a variety of surface types.

Higher reference levels of organic surface contamination on door handles in public toilets are likely related to more frequent use. A study of public toilets in Kathmandu, Nepal, found a linear correlation between usership estimated through structured observations and bacterial surface contamination ⁶². In our study, site representatives were surveyed on the estimated number of daily toilet users; however, reported estimates may have limited accuracy, especially for sites without toilet attendants. Higher levels of contamination at public toilet sites are consistent with other findings that overall quality is poorer and user satisfaction lower for open-use public versus shared residential toilets or when the latter is shared among more households ^34,63,64. Given substantial use and population mixing, promoting regular cleaning and disinfection of high-touch surfaces, which are a significant pathway for the transfer of pathogens ^18,19, is critical for shared toilets, especially public toilets. This may be achieved through cleaning practice improvement interventions that establish cleaning protocols and employ participatory approaches for designing behavior change and organizational strategies that address contextual constraints ^13,56,62.

This study has several limitations. Toilet sites were selected as a convenience sample, targeting facilities with high use, and therefore may not be representative of shared toilets outside of the neighborhoods where the study took place. The greatest variability in ATP sampling measures is known to occur between individuals taking samples ³³, and so where possible adjacent paired swabs should be taken from target surfaces. However, in this study, most swabbing was conducted on inner door handles, which did not have enough surface area for two paired 100 cm² swabs to be taken by different research enumerators. Additionally, door handle swabbing surfaces were not flat, and so approximations of ~100cm² may have varied. Given repeated sampling of the same surfaces, post-disinfection reductions may in part reflect study procedures from previous visits; however, all cleaning and disinfection assessment visits were conducted at least 7 days apart to minimize artificial impacts of study procedures. Due to travel restrictions, trainings of research enumerators for the initial assessment were conducted virtually whereas trainings for the cleaning and disinfection assessment were carried out in-person in the field. This may have led to differences in swabbing technique and ATP measurements between the two assessments, as ATP levels were lower in the initial assessment compared to reference levels in the cleaning and disinfection assessment. These differences were consistent across the whole sample and for the subset of toilets in the cleaning and disinfection assessment, and, as visits occurred within the same season, there was no apparent rainy versus dry seasonality.

Findings from this study demonstrate that cleaning and disinfection practices in low-resource shared toilets can be assessed using ATP testing, while also highlighting the need to use effective cleaning and disinfection procedures and robust assessment methods that target surface contamination that is indiscernible by visual assessment. ATP testing may be a useful complement to observational methods for studies that assess cleanliness when testing objectives align with the method’s non-specific target material (i.e., all living and non-living biologic material) and given careful consideration of potential barriers to application (e.g., challenges properly identifying surfaces for testing) ²². Further evaluation of ATP testing against standard microbiologic surface testing methods should be undertaken to identify ATP levels that indicate adequate removal of fecal and/or pathogenic contamination to establish standardized cleanliness benchmarks for this setting.