Source-pathway-sink framework to guide surface bacterial risk assessment and control in residential bathroom

Surfaces in residential bathrooms are hotspots for pathogenic bacteria. However, the lack of a comprehensive framework for assessing and controlling bacterial risks has hindered effective intervention strategies. To bridge this gap, this study combined both culture-independent and culture-dependent methods to establish a "source-pathway-sink" framework, which was used for analyzing bacterial risks on 72 bathroom surfaces across 12 households in China and the efficiencies of 9 risk control strategies. A total of 12 pathogens associated with 15 human diseases were identified on the sampled surfaces. Tap water was identified as the predominant bacterial source (54.0 %), challenging traditional assumptions about human-derived sources. Human gut was identified as the main occupant-derived source. Between 13.8 % and 83.3 % of bathroom surfaces exceeded the bacterial safety thresholds which were calculated by the reverse Quantitative Microbial Risk Assessment (QMRA) for Staphylococcus aureus. Evaluation of nine risk control strategies revealed that while sterilizing detergent achieved the highest efficiency (99 %), temporal analysis indicated the need for frequent reapplication (every 8–16 h), suggesting that effective risk management requires an integrated approach combining multiple control strategies. Our study provides valuable insights into bacterial risks assessment and control on bathroom surfaces.