sars cov 2 disinfection in aqueous solution by uv222 from a krypton chlorine excilamp CORD-Papers-2021-10-25 (Version 1)

Title: SARS-CoV-2 disinfection in aqueous solution by UV222 from a krypton chlorine excilamp
Abstract: There is an urgent need for evidence-based development and implementation of engineering controls to reduce transmission of SARS-CoV-2, the etiological agent of COVID-19. Ultraviolet (UV) light can inactivate coronaviruses, but the practicality of UV light as an engineering control in public spaces is limited by the hazardous nature of conventional UV lamps, which are Mercury (Hg)-based and emit a peak wavelength (254 nm) that penetrates human skin and is carcinogenic. Recent advances in the development and production of Krypton Chlorine (KrCl) excimer lamps hold promise in this regard, as these emit a shorter peak wavelength (222 nm) and are recently being produced to filter out emission above 240 nm. However, the disinfection kinetics of KrCl UV excimer lamps against SARS-CoV-2 are unknown. Here we provide the first dose response report for SARS-CoV-2 exposed to a commercial filtered KrCl excimer light source emitting primarily 222 nm UV light (UV222), using multiple assays of SARS-CoV-2 viability. Plaque infectivity assays demonstrate the pseudo-first order rate constant of SARS-CoV-2 reduction of infectivity to host cells to be 0.64 cm2/mJ (R2 = 0.95), which equates to a D90 (dose for 1 log10 or 90% inactivation) of 1.6 mJ/cm2. Through RT-qPCR assays targeting the nucleocapsid (N) gene with a short (<100 bp) and long (~1000 bp) amplicon in samples immediately after UV222 exposure, the reduction of ability to amplify indicated an approximately 10% contribution of N gene damage to disinfection kinetics. Through ELISA assay targeting the N protein in samples immediately after UV222 exposure, we found no dose response of the ability to damage the N protein. In both qPCR assays and the ELISA assay of viral outgrowth supernatants collected 3 days after incubation of untreated and UV222 treated SARS-CoV-2, molecular damage rate constants were similar, but lower than disinfection rate constants. These data provide quantitative evidence for UV222 doses required to disinfect SARS-CoV-2 in aqueous solution that can be used to develop further understanding of disinfection in air, and to inform decisions about implementing UV222 for preventing transmission of COVID19.
Published: 2/23/2021
DOI: 10.1101/2021.02.19.21252101
DOI_URL: http://doi.org/10.1101/2021.02.19.21252101
Author Name: Robinson, R T
Author link: https://covid19-data.nist.gov/pid/rest/local/author/robinson_r_t
Author Name: Mahfooz, N
Author link: https://covid19-data.nist.gov/pid/rest/local/author/mahfooz_n
Author Name: Rosas Mejia, O
Author link: https://covid19-data.nist.gov/pid/rest/local/author/rosas_mejia_o
Author Name: Liu, Y
Author link: https://covid19-data.nist.gov/pid/rest/local/author/liu_y
Author Name: Hull, N M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/hull_n_m
sha: b264712b44928d0163ea98d5664cb05212e985e8
license: medrxiv
source_x: MedRxiv; WHO
source_x_url: https://www.who.int/
url: https://doi.org/10.1101/2021.02.19.21252101 http://medrxiv.org/cgi/content/short/2021.02.19.21252101v1?rss=1
has_full_text: TRUE
Keywords Extracted from Text Content: UV222 SARS-CoV-2 KrCl SARS-46 CoV-2 human skin COVID19 aqueous https://doi host cells COVID-19 SARS-CoV-36 2 medRxiv coronaviruses RT-39 UV222 human surface stocks SARS-94 CoV-2 STEP 4 plane https://doi.org/10.1101/2021.02.19.21252101 doi Kr-Cl Test 1 S3 medRxiv CoV-2 pg//mL 6.51x10 4 SARS-CoV-2 convalescent patient eyes LR of 303 FORECAST Vero cells NIST-traceable 147 cDMEM eye COVID-19 medRxiv preprint skin Vero cell 10mJ/cm 2 SARS-CoV-2 427 Supplementary Table S1 tube LR of N1 copies/μL N1 stock Supplementary Figures S2 and Supplementary Figure S1 . R 2 Figures 1 copies/μL KrCl 106 excilamps Day 3 samples LR KrCl 0.8 + 1.4 copies/L N1-2 aqueous Day 3 cell KrCl excilamps
Extracted Text Content in Record: First 5000 Characters:There is an urgent need for evidence-based development and implementation of 25 engineering controls to reduce transmission of SARS-CoV-2, the etiological agent of 26 COVID-19. Ultraviolet (UV) light can inactivate coronaviruses, but the practicality of UV 27 light as an engineering control in public spaces is limited by the hazardous nature of 28 conventional UV lamps, which are Mercury (Hg)-based and emit a peak wavelength 29 (254 nm) that penetrates human skin and is carcinogenic. Recent advances in the 30 development and production of Krypton Chlorine (KrCl) excimer lamps hold promise in 31 this regard, as these emit a shorter peak wavelength (222 nm) and are recently being 32 produced to filter out emission above 240 nm. However, the disinfection kinetics of KrCl 33 UV excimer lamps against SARS-CoV-2 are unknown. Here we provide the first dose 34 response report for SARS-CoV-2 exposed to a commercial filtered KrCl excimer light 35 source emitting primarily 222 nm UV light (UV222), using multiple assays of SARS-CoV-36 2 viability. Plaque infectivity assays demonstrate the pseudo-first order rate constant of 37 SARS-CoV-2 reduction of infectivity to host cells to be 0.64 cm 2 /mJ (R 2 = 0.95), which 38 equates to a D90 (dose for 1 log10 or 90% inactivation) of 1.6 mJ/cm 2 . Through RT-39 qPCR assays targeting the nucleocapsid (N) gene with a short (<100 bp) and long 40 (~1000 bp) amplicon in samples immediately after UV222 exposure, the reduction of 41 ability to amplify indicated an approximately 10% contribution of N gene damage to 42 disinfection kinetics. Through ELISA assay targeting the N protein in samples 43 immediately after UV222 exposure, we found no dose response of the ability to damage 44 the N protein. In both qPCR assays and the ELISA assay of viral outgrowth 45 supernatants collected 3 days after incubation of untreated and UV222 treated SARS-46 CoV-2, molecular damage rate constants were similar, but lower than disinfection rate 47 constants. These data provide quantitative evidence for UV222 doses required to 48 disinfect SARS-CoV-2 in aqueous solution that can be used to develop further 49 understanding of disinfection in air, and to inform decisions about implementing UV222 50 for preventing transmission of COVID19. 51 52 All rights reserved. No reuse allowed without permission. 53 54 55 56 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted February 23, 2021. ; https://doi. (mercury from breaking fragile quartz lamp bulbs is toxic 23 ), (2) the UV dose response 87 kinetics needed to inactivate SARS-CoV-2 are unknown. Should these two challenges 88 be overcome, the use of UV to inactivate SARS-CoV-2 in environments with high 89 potential for transmission (e.g. congregate care facilities, convalescent patient homes, 90 hospital waiting rooms, airplane cabins) would be a practical and readily deployed 91 engineering solution to augment current prophylactic measures (social distancing, face 92 masks, vaccines). Due to a surge in interest and application of UV in various public 93 settings, there is an urgent need to understand the dose response kinetics of SARS-94 CoV-2 to UV radiation to inform decisions which balance the risk to eyes and skin from 95 Krypton and chlorine in KrCl excilamps are much less toxic than mercury, and KrCl 106 excilamps have already been shown to be competitive in terms of electrical efficiency 107 with mercury lamps that have many more years of product development and 108 optimization 30 . Our results demonstrate that when an aqueous solution of pathogenic 109 SARS-CoV-2 is exposed to UV222 light emitted by a Kr-Cl excilamp, its infectivity and 110 integrity is attenuated in a UV dose-dependent manner, as measured by culture and 111 molecular assays. These first UV222 disinfection dose responses demonstrate the 112 METHODS diffusing cosine corrector detector. Raw spectral data from the OceanView software 142 was interpolated to integer wavelengths using the FORECAST function in Microsoft 143 Excel and relativized to peak emission at 222 nm for use in dose calculations (Figures 1 144 and S1). Total incident UV-C irradiance was measured using an International Light 145 Technologies (ILT) 2400 radiometer with a SED 220/U solar blind detector, W Quartz 146 wide eye diffuser for cosine correction, and peak irradiance response NIST-traceable 147 calibration. For irradiance measurement, the peak wavelength calibration value was 148 input manually as the radiometer factor. The incident irradiance was measured with the 149 detection plane of the radiometer centered at the height and location of the sample 150 surface during UV exposures, and corrected for several factors to determine the 151 average irradiance through the sample depth. Spatial nonuniformity of emission
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