Viruses such as SARS-CoV-2 can be partially shielded from UV radiation when in particles generated by sneezing or coughing: Numerical simulations

Doughty, D.; Hill, Steven C.; Mackowski, Daniel W.

doi:10.1016/j.jqsrt.2020.107489

Cited by 17 publications

(18 citation statements)

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“…The methods of calculating the UV intensities and estimating the optical properties of the virions and dried respiratory fluids were described in Doughty et al (2021). If a UV planewave propagates in a material with complex refractive index m r + i m i , the intensity of the irradiance of the wave at position ( z ) is I(z) = I o exp( -z/δ) .…”

Section: Methodsmentioning

confidence: 99%

“…The virions were approximated as homogenous 100-nm diameter spheres with optical properties chosen to approximate SARS-CoV-2 virions. The enclosing spheres have optical properties selected to approximate dried respiratory fluids as described in Doughty et al, (2021). For illumination with a plane wave having an intensity of irradiance I o , the net rate of energy absorption by the i th virion is , where a i is the radius and Q abs, i is the absorption efficiency, each for the i th virion.…”

Section: Methodsmentioning

confidence: 99%

“…The results in Fig. 3 suggest an additional benefit of highly UVreflective surfaces, i.e., helping to achieve illumination with multiple beams where the angular differences between the angles of incidence with respect to the surface is relatively large (see Doughty et al, (2021) for the Ri distributions).…”

Section: Average Survival Fractions Are Reduced With Uv Light From Mumentioning

confidence: 98%

“…A problem with using UVGI to inactivate microbes is that in certain cases viruses and bacteria can be partially shielded from UVGI by being within or on particles (Osman et al, 2008; Kesavan et al, 2014; Handler and Edmonds, 2015; Doughty et al, 2021) or by clumping of particles (Coohill and Sagripanti, 2008). Numerical simulations of spherical dried droplets of respiratory fluids containing spherical 100-nm virions to simulate SARS-CoV-2 showed that virions in dried particles of respiratory fluids can be partially protected from UV radiation (Doughty et al, 2021). That study showed that partial shielding from UV occurs in particles whether they are on a surface or not.…”

Section: Introductionmentioning

confidence: 99%

“…Here the average survival fractions are calculated for virions of SARS-CoV-2 (approximated as 100-nm spherical particles) within otherwise homogeneous spherical particles having optical properties to approximate dried particles of sneezed or coughed respiratory fluids. The particles, incident beams, wavelengths and surfaces are as in Doughty et al (2021): three sizes (1-, 5- and 9-µm), two UV wavelengths (260 and 302 nm), and several combinations of incident beams and directions. Also, the particles are on a surface or in air.…”

Section: Introductionmentioning

confidence: 99%

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Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions

Hill

Doughty

Mackowski³

2021

Preprint

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Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions Steven C. Hill, David C. Doughty, and Daniel W. Mackowski DEVCOM Army Research Laboratory, 2800 Powder Mill Rd., Adelphi, Maryland, USA (Hill and Doughty); Auburn University, Auburn, Alabama, USA (Mackowski) #Address correspondence to Steve Hill, steven.c.hill32.civ@mail.mil ABSTRACT SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations within the particle. Shielding has been demonstrated in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions that are within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to calculate the survival fractions of virions (i.e., the fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. In this paper the survival fraction (S) of a set of virions illuminated with a UV fluence (F, in J/m2) is approximated as S=exp(-kF), where k is the UV inactivation rate constant (m2/J). The average survival fractions (Sp) of all the simulated virions in a particle are calculated using the calculated decreases in fluence. The results show that virions in particles of dried respiratory fluids can have significantly larger Sp than do individual virions. For individual virions, and virions in 1, 5, and 9 µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the Sp = 0.00005, 0.0155, 0.22 and 0.28, respectively, when kF=10. The Sp decrease to <10-7, <10-7, 0.077 and 0.15, respectively, for kF=100. Calculated results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the Sp. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important in effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the Sp. The results suggest the need for measurements of the Sp of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Average Survival Fractions Are Reduced With Uv Light From Mumentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions

Hill

Doughty

Mackowski³

2021

Preprint

Self Cite

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Design, Fabrication, and Testing of a Solar Powered Air Purifier with UV Sterilization Capability

Arora¹,

Bhardwaj²,

Esmail³

et al. 2022

Lecture Notes in Mechanical Engineering

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Principles and practice for SARS-CoV-2 decontamination of N95 masks with UV-C

Huber

Goldman

Epstein

et al. 2021

Biophysical Journal

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A mainstay of personal protective equipment during the coronavirus disease 2019 pandemic is the N95 filtering facepiece respirator. N95 respirators are commonly used to protect healthcare workers from respiratory pathogens, including the novel coronavirus severe acute respiratory syndrome coronavirus 2, and are increasingly employed by other frontline workers and the general public. Under routine circumstances, these masks are disposable, single-use items, but extended use and reuse practices have been broadly enacted to alleviate critical supply shortages during the coronavirus disease 2019 pandemic. Although extended-time single use presents a low risk of pathogen transfer, repeated donning and doffing of potentially contaminated masks presents increased risk of pathogen transfer. Therefore, efficient and safe decontamination methods for N95 masks are needed to reduce the risk of reuse and mitigate local supply shortages. Here, we review the available literature concerning use of germicidal ultraviolet-C (UV-C) light to decontaminate N95 masks. We propose a practical method for repeated point-of-use decontamination using commercially available UV-C cross-linker boxes from molecular biology laboratories to expose each side of the mask to 800-1200 mJ/cm 2 of UV-C. We measure the dose that penetrated to the interior of the respirators and model the potential germicidal action on coronaviruses. Our experimental results, in combination with modeled data, suggest that such a UV-C treatment cycle should induce a >3-log-order reduction in viral bioburden on the surface of the respirators and a 2-log-order reduction throughout the interior. We find that a dose 50-fold greater does not impair filtration or fit of 3M 8210 N95 masks, indicating that decontamination can be performed repeatedly. As such, UV-C germicidal irradiation is a practical strategy for small-scale point-of-use decontamination of N95s.

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Viruses such as SARS-CoV-2 can be partially shielded from UV radiation when in particles generated by sneezing or coughing: Numerical simulations

Cited by 17 publications

References 77 publications

Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions

Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions

Design, Fabrication, and Testing of a Solar Powered Air Purifier with UV Sterilization Capability

Principles and practice for SARS-CoV-2 decontamination of N95 masks with UV-C

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