Efficacy of single pass UVC air treatment for the inactivation of coronavirus, MS2 coliphage and Staphylococcus aureus bioaerosols

William J. Snelling, Arsalan Afkhami, Hannah L. Turkington, Claire Carlisle, S. Louise Cosby, Jeremy W.J. Hamilton, Nigel G. Ternan, Patrick S.M. Dunlop

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5 Citations (Scopus)
35 Downloads (Pure)

Abstract

There is strong evidence that SARS-CoV-2 is spread predominantly by airborne transmission, with high viral loads released into the air as respiratory droplets and aerosols from the infected subject. The spread and persistence of SARS-CoV-2 in diverse indoor environments reinforces the urgent need to supplement distancing and PPE based approaches with effective engineering measures for microbial decontamination – thereby addressing the significant risk posed by aerosols. We hypothesized that a portable, single-pass UVC air treatment device (air flow 1254 L/min) could effectively inactivate bioaerosols containing bacterial and viral indicator organisms, and coronavirus without reliance on filtration technology, at reasonable scale. Robust experiments demonstrated UVC dose dependent inactivation of Staphylococcus aureus (UV rate constant (k) = 0.098 m 2/J) and bacteriophage MS2, with up to 6-log MS2 reduction achieved in a single pass through the system (k = 0.119 m 2/J). The inclusion of a PTFE diffuse reflector increased the effective UVC dose by up to 34% in comparison to a standard Al foil reflector (with identical lamp output), resulting in significant additional pathogen inactivation (1-log S. aureus and MS2, p < 0.001). Complete inactivation of bovine coronavirus bioaerosols was demonstrated through tissue culture infectivity (2.4-log reduction) and RT-qPCR analysis – confirming single pass UVC treatment to effectively deactivate coronavirus to the limit of detection of the culture-based method. Scenario-based modelling was used to investigate the reduction in risk of airborne person-to-person transmission based upon a single infected subject within the small room. Use of the system providing 5 air changes per hour was shown to significantly reduce airborne viral load and maintain low numbers of RNA copies when the infected subject remained in the room, reducing the risk of airborne pathogen transmission to other room users. We conclude that the application of single-pass UVC systems (without reliance on HEPA filtration) could play a critical role in reducing the risk of airborne pathogen transfer, including SARS-CoV2, in locations where adequate fresh air ventilation cannot be implemented.

Original languageEnglish
Article number106003
Number of pages1
JournalJournal of Aerosol Science
Volume164
Early online date26 Apr 2022
DOIs
Publication statusPublished (in print/issue) - 31 Aug 2022

Bibliographical note

Funding Information:
This research was partly funded through the Invest Northern Ireland Innovation Voucher Programme (IV130218200 and IV130232906). We are grateful to the Global Challenges Research Fund (GCRF) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1) for supporting Mr Arsalan Afkhami, Dr William J Snelling and Dr Jeremy W.J. Hamilton. Research at AFBI is funded by US-Ireland Research and Development Partnership in Agriculture grants BRDC-Seq and BRDC-URTMVP. We wish to thank Jonathan McMaw at AFBI for acquisition of images.

Funding Information:
This research was partly funded through the Invest Northern Ireland Innovation Voucher Programme ( IV130218200 and IV130232906 ). We are grateful to the Global Challenges Research Fund ( GCRF ) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1) for supporting Mr Arsalan Afkhami, Dr William J Snelling and Dr Jeremy W.J. Hamilton. Research at AFBI is funded by US-Ireland Research and Development Partnership in Agriculture grants BRDC-Seq and BRDC-URTMVP. We wish to thank Jonathan McMaw at AFBI for acquisition of images.

Publisher Copyright:
© 2022 The Authors

Keywords

  • Air sterilisation
  • Air treatment
  • MS2
  • PTFE
  • SARS-CoV-2
  • UVC

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