Moura et al.
10.3389/fpubh.2025.1664322
Introduction
that can contaminate standby users’ masks (as a proxy of inhalation risk) during and following hand drying.
Hand drying is an important step of hand hygiene, that complements hand washing by assisting with the removal of microbial contamination from hands (1). This step became additionally important during the COVID-19 pandemic, as appropriate hand washing practices increased with the public awareness to their role in reducing the virus spreading through contaminated surfaces (2–4). However, the end of social restrictions has been accompanied by a decline in compliance with good hand hygiene practices (3, 4). This change in behavior away from recommended guidelines (5) can have public health implications. Respiratory infections caused by SARS-CoV-2, influenza and other respiratory virus have been rising in Western countries since 2021 (6–9), leading to variable uptake of facemask use, notably for enhanced protection of those more susceptible to severe disease (10, 11). However, as influenza and SARS-CoV-2 virus can also survive on contaminated hands and surfaces in community settings (12, 13), there is an increased risk of viral spread in contaminated environments, namely hospitals, that are often used by susceptible individuals. Previous studies have shown PT are more effective at removing moisture and pathogens from hands (1, 14–17), compared to the jet air dryer or warm air dryer models. PT were also associated with a lower potential to disperse droplets (18–22) and lower particle aerosolization (20, 22). Jet air dryers have been associated with droplet dispersion up to 1.5 m for viral particles (21) and over 3 m for bacterial particles (23). These results demonstrate the potential risk of airborne dissemination of microbial pathogens during and following hand drying, according to the method used. New high-speed electric hand drying systems (Figure 1A) have become available, including some that combine hand washing and drying (Figure 1B) in a small footprint and are commonly found in high traffic public toilets such as in airports, hospitals, and train stations. The potential of these systems to disseminate droplets or aerosolized particles that can remain in the environment and contaminate others for an extended period after hand drying remains poorly studied. Therefore, using a bacteriophage as surrogate for hand microbial contamination we investigated: (i) whether different hand drying methods impacted the residual microbial contamination remaining on hands following hand drying of poorly washed hands and, (ii) the potential of each hand drying method to promote aerosolization of bacteriophage particles
Materials and methods Food dye assays to assess washroom contamination following hand drying A total of 3 hand drying methods were investigated: Dyson Airblade 9 kJ (A9KJ) hand dryer, the Dyson Airblade Wash+Dry (AW+D) wall dryer, and paper towels (PT). Both the A9KJ and AW+D dryer have a 2-arm design and are activated by placing the hands beneath the dryer arms and moving them parallel to the dryer surface. However, with the A9KJ hands are dried at a 30-degree flexion with an outlet air velocity of 158 m/s, whereas using the AW+D wall dryer, hands are extended horizontally and dried with an air velocity of 153 m/s. For each method, 3 hand drying assays were performed to assess droplet dispersion within the washroom environment. A power calculation was not performed as the purpose of these experiments was to visually assess the droplet contamination caused by each method and to inform the surfaces to be tested in the subsequence bacteriophage assays. Hand dryer users immersed their hands in 10 mL of food dye solution and performed hand drying following manufacturer recommendations for each method, i.e., 10s with A9KJ hand dryer, 14 s with Dyson AW+D wall hand dryer, or using 3 PT. All experiments were performed in presence of a standby user stationed at ~1 m distance from the hand drying station. During hand drying, all participants wore personal protective equipment including a disposable Tyvek protective suit (DuPont, Stevenage, United Kingdom) and face shields (Fisher Scientific, UK) for visual assessment of user contamination. Furthermore, selected areas were monitored to determine the level of droplet dispersion caused by each hand drying method, namely: (i) wall and floor sections of 65 cm x 40 cm both underneath the dryer and at 1 m distance, corresponding to the width and length of space occupied by an average person while standing still, (ii) a visor shield surface of 32 cm x 22 cm, representing the face area exposed to droplets, (iii) Tyvek suit torso and leg areas of 16 cm x 22 cm, selected based on the shortest hand drying volunteer. Splattering was measured by counting
FIGURE 1 Schematics of droplet dispersion observed with each hand drying method. Arrows represent the widest angle and longest distance traveled by droplets following hand drying with (A) paper towels, (B) Dyson AW+D wall hand dryer, (C) Dyson A9KJ hand dryer.
Frontiers in Public Health
02
frontiersin.org
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