Mapping of UV-C dose and SARS-CoV-2 viral inactivation across N95 respirators during decontamination

Alisha Geldert,Sarah A Stanley,Amy E Herr,Alison Su,Guillaume Golovkine,Allison W Roberts,Samantha M Grist

doi:10.1038/s41598-021-98121-6

Alisha Geldert, Sarah A Stanley + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-98121-6

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Abstract

During public health crises like the COVID-19 pandemic, ultraviolet-C (UV-C) decontamination of N95 respirators for emergency reuse has been implemented to mitigate shortages. Pathogen photoinactivation efficacy depends critically on UV-C dose, which is distance- and angle-dependent and thus varies substantially across N95 surfaces within a decontamination system. Due to nonuniform and system-dependent UV-C dose distributions, characterizing UV-C dose and resulting pathogen inactivation with sufficient spatial resolution on-N95 is key to designing and validating UV-C decontamination protocols. However, robust quantification of UV-C dose across N95 facepieces presents challenges, as few UV-C measurement tools have sufficient (1) small, flexible form factor, and (2) angular response. To address this gap, we combine optical modeling and quantitative photochromic indicator (PCI) dosimetry with viral inactivation assays to generate high-resolution maps of “on-N95” UV-C dose and concomitant SARS-CoV-2 viral inactivation across N95 facepieces within a commercial decontamination chamber. Using modeling to rapidly identify on-N95 locations of interest, in-situ measurements report a 17.4 ± 5.0-fold dose difference across N95 facepieces in the chamber, yielding 2.9 ± 0.2-log variation in SARS-CoV-2 inactivation. UV-C dose at several on-N95 locations was lower than the lowest-dose locations on the chamber floor, highlighting the importance of on-N95 dose validation. Overall, we integrate optical simulation with in-situ PCI dosimetry to relate UV-C dose and viral inactivation at specific on-N95 locations, establishing a versatile approach to characterize UV-C photoinactivation of pathogens contaminating complex substrates such as N95s.

Highlights

During public health crises like the COVID-19 pandemic, ultraviolet-C (UV-C) decontamination of N95 respirators for emergency reuse has been implemented to mitigate shortages
We develop an optical modeling workflow to characterize UV-C dose distribution across N95s within a decontamination chamber to rapidly iterate on experimental design, and simultaneously inform and validate this model using in-situ photochromic indicator (PCI) dose quantification
We sought to understand the impact of N95 shape and placement on SARS-CoV-2 inactivation and how variation in inactivation relates to UV-C dose received across the N95 surfaces (Fig. 1A)

Summary

Introduction

During public health crises like the COVID-19 pandemic, ultraviolet-C (UV-C) decontamination of N95 respirators for emergency reuse has been implemented to mitigate shortages. Due to nonuniform and system-dependent UV-C dose distributions, characterizing UV-C dose and resulting pathogen inactivation with sufficient spatial resolution on-N95 is key to designing and validating UV-C decontamination protocols. Robust quantification of UV-C dose across N95 facepieces presents challenges, as few UV-C measurement tools have sufficient (1) small, flexible form factor, and (2) angular response To address this gap, we combine optical modeling and quantitative photochromic indicator (PCI) dosimetry with viral inactivation assays to generate high-resolution maps of “on-N95” UV-C dose and concomitant SARS-CoV-2 viral inactivation across N95 facepieces within a commercial decontamination chamber. Other approaches use optical modeling to estimate the UV-C distribution across N95 surfaces from the UV-C dose measured in a single location, in order to relate approximate UV-C dose to SARS-CoV-2 inactivation[22]. The high resolution and rapid iteration capabilities of optical simulations would be most valuable when coupled with in-situ validation measurements

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