Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads
Abstract
:1. Introduction
2. Materials and Methods
2.1. Coupon Materials
2.2. Aerosol Deposition onto Coupons
2.3. Production and Characterization of Artificial Finger-Pads
2.4. Measurement of Surface Energy and Dynamic Contact Angles
2.5. Determination of Transfer Efficiency from Coupon to Artificial Finger-Pad
2.6. Quantitative Microbial Risk Assessment (QMRA) Modeling
2.6.1. Development of Linear Regression Model of Transfer Efficiency Data
2.6.2. Analysis of Effect of Environmental Factors on Risk of Fomite Transmission
2.7. Statistical Analysis
3. Results
3.1. Development of a Standardized Experimental Process for Aerosol Deposition onto and Recovery from Surfaces
3.1.1. Characterization of Coupon Surfaces
3.1.2. Aerosol Deposition
3.2. Development of Artificial Finger-Pad with Characteristics of Human Finger Touch
3.2.1. Topological Detail and Effective Contact Area
3.2.2. Influence of Sweat and Sebum Finger-Pad Wettability on Transfer
3.3. Transfer of Artificial and Human Saliva from Surfaces to Artificial Finger-Pads
3.3.1. Relative Humidity and Surface Complexity Influence Transfer of Artificial and Human Saliva
3.3.2. Development of a Regression Model for Humidity and Impact in QMRA Model
4. Discussion
5. Conclusions
- Transfer efficiency increases with increasing humidity for all materials studied. At RH <40%, transfer from all surfaces was <10%, and increased markedly as RH increased, reaching a maximum of approximately 50%.
- The quantity of material transferred at specific RHs above 40% was dependent on the roughness of the surface material and the properties of the aerosol-deposited material. Smooth surfaces, such as melamine and stainless steel, generated higher transfer efficiencies compared to those with textured roughness, such as ABS pinseal and KYDEX® plastics.
- Pooled human saliva was transferred at a lower rate compared to artificial saliva, indicating the role of rheological properties.
- QMRA analysis using SARS-CoV-2 suggests that the highest risks of fomite transmission are likely in indoor environments with normal temperatures (around 22 °C) and higher humidity (>65% RH). This suggests humid spaces could pose a higher risk.
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Coupon Surface | Example High-Touch Surfaces Represented | Roughness Profile Parameters 1 | Surface Energy (mN·m−1) 2 | Contact Angles 3 | |||
---|---|---|---|---|---|---|---|
Ra | Rq | Rz | θAdv; θRec | Δθr | |||
SS304 | Door handles, hand poles, keypads, taps, cutlery | 0.167 ± 0.024 | 0.250 ± 0.046 | 4.05 ± 0.73 | 26.3 ± 0.26 | 80.6; 44.3 | 14.2 |
ALU | Door push plates, handrails, furniture handles | 0.454 ± 0.037 | 0.639 ± 0.048 | 6.94 ± 1.34 | 25.8 ± 0.36 | 92.7; 35.3 | 23.2 |
MEL | Table surfaces, kitchen cabinets, decorative panels | 0.419 ± 0.024 | 0.524 ± 0.038 | 3.57 ± 0.71 | 29.2 ± 0.52 | 93.9; 38.2 | 20.3 |
ABSS 4 | Entry/exit press, keypads, sockets, housing, dashboard | 0.127 ± 0.014 | 0.174 ± 0.017 | 1.73 ± 0.097 | 28.9 ± 0.23 | 72.2; 47.4 | 11.1 |
ABST 4 | Entry/exit press, keypads, sockets, housing, dashboard | 33.11 ± 0.67 | 38.87 ± 0.78 | 165.7 ± 10.8 | 33.7 ± 0.43 | 73.8; 32.1 | 26.4 |
KYD 4 | Trays, storage lockers, hand rests, seat backs, holsters | 4.49 ± 0.186 | 5.53 ± 0.245 | 30.3 ± 1.81 | 28.3 ± 0.32 | 82.5; 43.5 | 15.0 |
Silicone 5 | No sweat–sebum Sweat–sebum | ND | ND | ND | 26.7 ± 0.37 ND | 82.6; 68.4 68.9; 58.5 | ND |
Art. silicone finger-pad | No sweat–sebum Sweat–sebum | ND | ND | ND | 28.2 ± 0.34 56.2 ± 0.72 | ND |
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Walker, M.D.; Vincent, J.C.; Benson, L.; Stone, C.A.; Harris, G.; Ambler, R.E.; Watts, P.; Slatter, T.; López-García, M.; King, M.-F.; et al. Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads. Viruses 2022, 14, 1048. https://doi.org/10.3390/v14051048
Walker MD, Vincent JC, Benson L, Stone CA, Harris G, Ambler RE, Watts P, Slatter T, López-García M, King M-F, et al. Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads. Viruses. 2022; 14(5):1048. https://doi.org/10.3390/v14051048
Chicago/Turabian StyleWalker, Maurice D., Jack C. Vincent, Lee Benson, Corinne A. Stone, Guy Harris, Rachael E. Ambler, Pat Watts, Tom Slatter, Martín López-García, Marco-Felipe King, and et al. 2022. "Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads" Viruses 14, no. 5: 1048. https://doi.org/10.3390/v14051048
APA StyleWalker, M. D., Vincent, J. C., Benson, L., Stone, C. A., Harris, G., Ambler, R. E., Watts, P., Slatter, T., López-García, M., King, M.-F., Noakes, C. J., & Thomas, R. J. (2022). Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads. Viruses, 14(5), 1048. https://doi.org/10.3390/v14051048