Moura et al.
10.3389/fpubh.2025.1664322
Results
hand dryer (Table 2). Contamination of the floor area around the hand drying unit/user was on average 3 times higher with A9KJ hand dryer compared with AW+D wall hand dryer and 14 times higher compared with PT. At 1 m from the drying station, droplet levels observed following A9KJ hand dryer use were similar to those observed using the AW+D wall hand dryer, but >8 times higher than following PT use. Contamination on the wall next to the drying station was 78 times higher with A9KJ and 19 times higher using the AW+D wall hand dryer, compared with PT. Wall contamination following PT use was associated with liquid displacement from hands when removing PT from the holder unit, whereas floor contamination resulted of droplet dripping during the hand drying movements. Droplets traveled longer distances following A9KJ hand dryer use, up to 90 cm in a straight line and up to 55 cm in an angle (Figure 1). However, the user and standby user contamination was higher on the assays performed with AW+D wall hand dryer, for nearly all areas of the Tyvek suit analyzed, particularly on the torso of the hand dryer user (Table 2; Supplementary Figure 2). Although the A9KJ hand dryer was associated with high floor contamination at 1 m from the drying unit, almost no droplets were observed on the standby user. Overall, PT was the method associated with lower person contamination, with no droplets observed in the Tyvek suit or visor of the standby user, and under 10 droplets observed on the hand drying volunteers’ suit (Supplementary Figure 3). Surface contamination was also lower with PT, compared with the other methods, with most droplets observed on the wall traveling up to 15 cm (Figure 1).
Overall, nine hand drying assays were performed using a food dye and either the Dyson A9KJ hand dryer, the Dyson AW+D wall hand dryer or PT, to determine the potential for droplet dispersion in the room environment via splattering and aerosolization of particles. Sixty hand drying assays were also performed using a bacteriophage solution to determine the potential for microbial contamination of hands, surfaces and facemasks using either Dyson A9KJ hand dryer, Dyson AW+D wall hand dryer or PT, in presence and absence of poor hand washing. Hands contaminated with the bacteriophage solution aimed to represent hands not washed following the recommended guidelines (25), i.e., hands that have not been washed with water and soap for 20s. Each assay involved 2 volunteers: one performing the hand drying and other stationed at 1 m distance. User and surface contamination as result of splattering The potential of each hand drying method to disperse water droplets in the washroom environment, potentially contaminating surfaces, the user, and the bystander was investigated using a food dye solution as visual indicator for contamination. Contamination was measured within predefined areas of the room and of the Tyvek suits/ face shields worn by the volunteers. The highest level of droplet contamination on the washroom surfaces (floor and wall) was observed in the assays using the A9KJ
TABLE 1 Primer sequences used for amplification of the P3 gene of bacteriophage PR772 via qPCR.
Primer
Sequence
Amplicon size (bp)
Reference
P3 Forward
5 -CCCATTAAGTACGGCGATGTTATG-3
102
(38)
P3 Reverse
5 -GGCAAGCGGAACCCAATAG-3
TABLE 2 Droplet dispersion observed following hand drying assays performed using food dye.
Surface area (cm x cm)
Paper towels
AW+D wall hand dryer
Airblade 9KJ
Wall (65 × 40)
7 ± 1
139 ± 87
536 ± 277
Floor – immediately underneath the hand dryer (65 × 40)
32 ± 5
158 ± 34
466 ± 277
Floor – 1 m behind hand dryer (65 × 40)
13 ± 6
135 ± 32
104 ± 13
Floor – 1 m at a 45-degree angle from hand dryer (65 × 40)
5 ± 5
109 ± 29
93 ± 33
Hand drying person (cm x cm) Face shield (32 × 22)
0
56 ± 30
7 ± 4
8 ± 5
46 ± 25
Torso (22 × 16)
288 * ± 65
Leg (22 × 16)
3 ± 2
35 ± 8
61 ± 31
Standby user (cm x cm) Face shield (32 × 22)
0
62 ± 4
0
Torso (22 × 16)
0
60 ± 22
1 ± 0.8
Leg (22 × 16) 0 Contamination of surfaces, the individual performing hand drying and a standby user stationed a 1 m distance were investigated with three different hand drying methods. Data shown is the average of three hand drying experiments and standard deviation. * Average of 2 assays, as in the third the spots were too many to count. 0 56 ± 30
Frontiers in Public Health
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