Moura et al.
10.3389/fpubh.2025.1664322
Contamination of surfaces and N95 masks by microbial droplets
above the limit of detection in this position was observed in 80% of the PT assays, whereas electric hand dryers resulted in 100% of tests positive for bacteriophage presence in facemasks. Similarly, mask contamination of participants standing at 1 m distance of the hand drying unit was 10-fold and 100-fold lower in assays using PT, when compared to the use of A9KJ hand dryer and AW+D wall hand dryer, respectively. (Figure 2). At this position, facemasks contamination with bacteriophage was observed in 100% of the assays using electric hand dryers, but only in 70% of the assays using PT. Compared to the electric hand dryers, PT resulted in significantly less splattering contamination of both masks and aprons at both investigated positions. This was particularly evident on the hand drying position where the electric methods were associated with 100- to 1,000-fold more apron contamination (Figure 2). For most surfaces tested, AW+D wall hand dryer resulted in a significantly higher facemask contamination compared to both A9KJ hand dryer and PT. The one exception was observed on the splattering of facemasks used by the volunteers during hand drying, where A9KJ hand dryer was associated with the highest contamination.
Hand drying assays were also performed following hand immersion in a bacteriophage solution, to assess the efficacy of each method in supporting hand hygiene of poorly washed hands. Viral contamination as result of splattering was investigated by recovering N95 respirators and sampling disposable plastic aprons worn by volunteers and by standby users during hand drying. Hand contamination following hand drying significantly declined with all methods tested ( p < 0.05 on the Wilcoxon test), when compared to the stock solution used to contaminate the hands. However, hand contamination following drying was 10-fold lower using PT, when compared to the use of either electric hand dryer (Figure 2). This lower microbial load was associated with a significantly lower 100-fold contamination of the door handle when PT were used, compared to the AW+D wall hand dryer and A9KJ hand dryer ( p < 0.05 using a two-tailed Mann–Whitney test; Supplementary Figure 4). Among all methods, the bacteriophage transfer from hands to the door handle, was significantly higher following the use of the AW+D wall hand dryer, compared to the A9KJ hand dryer and PT. Mask contamination of the volunteers performing the hand drying of poorly washed hands was 200-fold and 1,000-fold lower following PT use (1.7 ×10 3 copies/ μ l) compared to the use of the AW+D wall hand dryer (3.4 ×10 5 copies/ μ l) and the A9KJ hand dryer (1.1 ×10 6 copies/ μ l), respectively (Figure 2). Mask contamination
Mask contamination as result of aerosols
After hand drying, the participants remained at their defined positions, i.e., by the hand drying station and at 1 m distance from the
FIGURE 2 Mean qPCR bacteriophage levels recovered from facemasks and torso of the individual performing the hand drying and the standby user at 1 m distance. Data shown is the average of 10 hand drying experiments with each method and standard deviation. * p < 0.05 significant differences between paper towels and Dyson AW+D wall hand dryer, and between PT and Dyson A9KJ hand dryer, using a two-tail Mann–Whitney U test. # p < 0.05 significant differences between Dyson AW+D wall hand dryer and Dyson A9KJ hand dryer using a two-tail Mann–Whitney U test.
Frontiers in Public Health
05
frontiersin.org
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