Moura et al.
10.3389/fpubh.2025.1664322
Facemask contamination via aerosols was significantly lower at all time points and distances investigated, following hand drying with PT, compared with using the Dyson AW+D wall hand dryer or the A9KJ hand dryer. However, bacteriophage deposition on facemasks increased at 30 min post-hand drying with all methods versus the 15 min timepoint, but this increase was 10-fold higher with AW+D wall hand dryer and A9KJ hand dryer, at the standby user position. Hand drying can result in aerosolization of different size particles, with those smaller than 0.5 mm not visible by the naked eye (33). Our data shows that AW+D and A9KJ result in a larger amount of droplets forming and dispersing in the environment compared to PT. Based on these observations, and reported data showing bacteria aerosols ranging from 0.3 μ M to 5 μ M are formed during hand drying (28), we hypothise that larger and smaller size particles containing bacteriophage are also formed that remain airborne for different periods of time. This appears to be consistent with the different size of bacterial aerosols collected using an air sampler, following hand washing and drying with different methods (28). Similar to many public spaces, the room used in our study has standard ventilation and hand drying assays were performed in sets of 5, to represent repeated use of public washrooms. The air displacement caused by repeated hand drying would support the smaller size viral particles remaining airborne for longer and traveling from the hand drying station to the standby user position at 1 m distance, where the largest increase in mask contamination was observed at 30 min post- hand drying. These results are similar also to those observed when testing the Dyson Airblade jet hand dryer (1, 20–22) and would mean a potential for prolonged exposure of others to microbial pathogens. Overall, in this study PT use resulted in lower hand, person, and surface contamination, compared with use of AW+D wall hand dryer and A9KJ hand dryer. However, our observations are limited by the room dimension and ventilation and therefore cannot represent every real-world setting. Different hand dryer models and variations in installation heights/angles could also impact droplet dispersion and aerosolization in public spaces. Studies looking at hand washing practices in the community have reported rates of hand washing with soap in adults as low as 11% (32), whereas a systematic review looking at global hand washing practices in the context of diarrheal diseases has estimated that only 19% of the world population washes their hands with soap after contact with excreta (30). Even when regular hand wash is performed with plain or antimicrobial soap, 4 to 6 log 10 colony forming units of bacteria have been reported to remain in hands (34–36). Considering how often hand washing is suboptimal, effective hand drying is essential to aid removal of microbes remaining on hands.
using PT compared with electric hand dryers. Although the use of facemasks to protect from SARS-CoV-2 is no longer common in the community, facemasks are still used in healthcare facilities and by at risk groups, particularly as viral respiratory infections remain high (7, 9, 11, 37). As poorly washed hands in become increasingly common once again (3, 4, 29–32), hand drying can act as supportive measure to reduce the viral transmission in enclosed environments. Our results demonstrate that hand drying with PT is associated with a lower risk of droplet and aerosol dispersal compared with use of electric hand dryers, particularly when hands are sub-optimally cleaned.
Data availability statement
The raw data supporting the conclusions of this article will be made available by the authors, upon reasonable request.
Author contributions
IM: Conceptualization, Formal analysis, Investigation, Methodology, Supervision, Writing – original draft. KB: Investigation, Writing – review & editing. KK: Investigation, Writing – review & editing. MW: Conceptualization, Funding acquisition, Resources, Writing – review & editing.
Funding
The author(s) declare that financial support was received for the research and/or publication of this article. The study was supported by the European Tissue Symposium. The funder was not involved in project design, data collection, analysis or interpretation, or in the manuscript preparation. IBM and MHW are supported in part by the National Institute for Health and Care Research (NIHR) Leeds Biomedical Research Center (BRC; NIHR203331). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.
Acknowledgments
We thank the volunteers that took part in the hand drying assays.
Conflict of interest
MW has received consulting fees from Astra Zeneca, BioInteractions, Centauri, Debiopharm, Ferring, GSK, Nestlé, Paion, Pfizer, Phico Therapeutics, The European Tissue Symposium, Tillotts. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Conclusion
This study investigated person, surface and mask contamination during and up to 30 min after three hand drying methods. Microbial contamination was significantly lower when
Frontiers in Public Health
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