Bioluminescence-based hygiene evaluation of public washroom environment: Repeated measurement of posthandwashing facilities on baseline and before and after cleaning schedule

Simon Ching Lam, Matthew Man Fai Cheung, Jessie Kit Ling Au, Lorna Kwai Ping Suen

Research output: Journal article publicationJournal articleAcademic researchpeer-review

1 Citation (Scopus)


Background: The risk of hand recontamination is often neglected after using hand washing facilities, which can increase the spread of pathogens. The study aimed to evaluate the hygienic condition of posthandwashing facilities in public washrooms at different timeslots, particularly those near food courts and restaurants located in shopping malls. 

Methods: This observational study was conducted in 12 public washrooms that ranged from low-end, middle-end, to high-end category on 3 different timeslots including baseline, T1 (immediate postcleaning) and T2 (1-hour postcleaning, with counting the footfall). Hand–touch surfaces with a high risk of recontamination after handwashing, which included paper tower dispensers, air drying outlets, and exit door handles, were evaluated by the surface adenosine triphosphate (ATP) bioluminescence method (ATP-value). ATP-values <500 relative light units (RLUs) were considered a good hygiene. Cleaning schedules and footfalls of each sampled washroom were obtained by direct observations. 

Results: The overall mean ATP value of washroom was 785 RLU (N = 108); the ATP values of female and male washrooms at T2 were 203 and 3,718 RLUs, respectively. The highest ATP value was found on the exit door handles of male washrooms (range = 13-26,695 RLUs, mean = 3,229 RLU). Regarding passed/failed hygiene conditions, there were significant differences in the proportion of exit door handles between genders (P = .018) and timeslots (P = .007) as well as that of paper towel button/screw between timeslots (P= .025).

 Conclusion: Attention should be paid at the exit door handles of male washrooms, where are high risks of cross and re-contamination.

Original languageEnglish
Pages (from-to)746-752
Number of pages7
JournalAmerican Journal of Infection Control
Issue number6
Publication statusPublished - Jun 2021


  • Adenosine triphosphate
  • Cross contamination
  • Exit door handle
  • Footfall
  • Re-contamination
  • Shopping mall

ASJC Scopus subject areas

  • Epidemiology
  • Health Policy
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases

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