Toileting behaviours of the UK public: insights for reducing demographic bias in wastewater-based epidemiology sampling strategies

Wastewater-based epidemiology has gained increasing interest for its application as a public health surveillance tool, yet the impact of toileting habits over the representativeness of wastewater data remains underexplored. To address this, we surveyed the toilet habits of the UK public ( n  = 2109). Most respondents defecated once daily (52%), with higher frequencies and morning defecation more common among male and older participants. Willingness to use facilities outside the home was lower for defecation than urination, and varied by location (from 32% at paid toilets to 75% at work). Cleanliness was the leading reason for avoiding public toilets (67%), while safety concerns were more frequently reported among females (43%). Those aged 18–24 were less willing to use public toilets than older participants, citing shyness at a higher proportion. These behavioural patterns suggest that composite or time-resolved grab sampling can help account for the demographic influence over diurnal toileting patterns. Furthermore, near-source studies— particularly in non-residential settings where toilet use is lower—should strongly consider detection sensitivity in their sampling design. Overall, we demonstrate that a deeper understanding of a population’s toilet habits is crucial to ensure wastewater surveillance can deliver effective public health insights.