key: cord-1007073-ell4zzr0
authors: Su, Wen-Lin; Lin, Chih-Pei; Huang, Hui-Ching; Wu, Yao-Kuang; Yang, Mei-Chen; Chiu, Sheg-Kang; Peng, Ming-Yieh; Chan, Ming-Chin; Chao, You-Chen
title: Clinical application of 222 nm wavelength ultraviolet C irradiation on SARS CoV-2 contaminated environments
date: 2022-01-13
journal: J Microbiol Immunol Infect
DOI: 10.1016/j.jmii.2021.12.005
sha: 282e08b054d50dce51b902b83a1faab372671b7e
doc_id: 1007073
cord_uid: ell4zzr0

This was a preliminary study on ultraviolet C (UVC) irradiation for SARS-CoV-2-contaminated hospital environments. Forty-eight locations were tested for SARS-CoV-2 using RT-PCR (33.3% contamination rate). After series dosages of 222-nm UVC irradiation, samples from the surfaces were negative at 15 s irradiation at 2 cm length (fluence: 81 mJ/cm2).

handheld lamp (USHIO Inc., Taiwan and Delta Electronics, Inc., Taiwan) emits 222-nm UVC 1 at 27mJ/cm2 after 5 s irradiation in a single room with a fixed length of 2 cm with stabilized 2 UV radiation intensity. For the purpose of the dosage-related cleaning effect, the irradiation 3 times were 5, 10, 15, 20 s. The fluences were 27, 54, 81, 108 mJ/cm 2 . Environmental samples 4

were collected again after radiation. 5 6

Continuous data are expressed as the mean ± standard error. Categorical data are expressed as 8 frequencies and percentages. The chi-square test was used to compare categorical variables 9 between the different UVC irradiation dosages. The linear trend was also tested using the chi-10 square test for UVC irradiation of the dose effect on SARS-CoV-2. The data were analyzed 11 using SPSS (version 24.0; IBM Corp., Armonk, NY, USA), and a p-value of <0.05 was 12 considered statistically significant. 13

Forty-eight environmental samples were collected. The total contamination rate was 33.3% ( Fig.  2 

To estimate the proper irradiation dosage of 222-nm UVC, a series of studies were conducted 4 to test its dose-related effect on SARS-CoV-2 contaminated environments. In the first survey, 5 four locations in each of the three isolation wards were selected for environmental sampling 6 before irradiation (Table 1) . Before irradiation, three (25.0%) were positively contaminated. 7 SARS-CoV-2 was completely inactivated after 15 s of 222-nm UVC irradiation. However, the 8 contamination was still present in three (25.0%) after 5 s of irradiation, and one (8.3%) after 10 9 s of irradiation, although the decrease was not statistically significant. The separate E and N 10 genes also decreased after irradiation, although this was not statistically significant. The internal 11 control also decreased slowly from 58.3% before the irradiation to 41.7%, 41.7%, and 25.0% 12 after 5, 10, and 15 s, respectively (p=0.433). 13

To determine the optimal UVC irradiation dose (fluence) for SARS-CoV-2 environmental 14 disinfection, repeated studies on the dose effect of UVC irradiation were conducted for 5-20 s 15 on the second-day survey of regular patient activity (Table 1) . SARS-CoV-2 was completely 16 inactivated after 15 s of 222-nm UVC irradiation. The positive contamination rates were 13/36 17 (36.1%) before irradiation and 3/36 (8.3%), 2/36 (5.6%), 0%, and 0% after 5, 10, 15, and 20 s 18 irradiation, respectively (p<0.001). The separate E and N genes showed the same decreasing 19 trend as the contamination rate from 16.7% and 36.1% before irradiation to 0% after 15 s 1 irradiation. The 15 s in 2 cm length had a fluence of 81 mJ/cm 2 , which was the optimal 222-nm 2 UVC dose. The internal control was the same 13/36 (36.1%) as the contamination rate of SARS-3

CoV-2 and slowly decreased with irradiation to 25.0%, 13.9%, 13.9%, and 11.1% after 5, 10, 4 15, and 20 s of irradiation, respectively (p=0.043).

Our preliminary study simulated the 222-nm UVC irradiation effect on the SARS-CoV-2 2 contaminated surfaces of the hospital isolation ward. The effective fluence was 81mJ/cm 2 with 3 an environmental SARS-CoV-2 eradication rate of 100%. 4

In traditional disinfection procedures, patients must leave the ward before 254-nm UVC 5 irradiation to prevent the risk of skin cancer and corneal damage. A SARS CoV2 in vitro study 6 showed 1-3 mJ/cm 2 222-nm UV irradiation reduced 88.5% to 99.7% of the SARS CoV2 virus 7 detected as 50% tissue culture infectious dose (TCID 50) 3 . In animal studies, 222-nm UV light 8 did not damage the hairless mouse skin 4 . Another hairless mouse skin study found no damage 9

to the skin after 10 days of 450 mJ/cm 2 /day chronic irradiation 5 . The corneas of Sprague Dawley 10 albino rats were not damaged by 222-nm UV light with a high exposure level of 600 mJ/cm 2 . 11

In an in vitro study of mammalian skin, 222-nm UV light did not yield UV-associated 12 premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) 4 . The 13

other simulated mice study showed Xpa knockout mice irradiated with a high dose of 222-nm 14 UVC, and there was no skin tumor formation 6 . In a clinical trial of 20 healthy humans, 222-nm 15 UV (500 mJ/cm 2 ) was found to be safe and have a bactericidal effect on the human skin after 3 16 months follow-up 7 . Therefore, 222-nm UVC has potential safety in a clean environment and 17 prevents skin damage compared to 254-nm UVC; however, further studies are needed. Far-UVC light (222 nm) with low doses of 1.7 and 1.2 mJ/cm 2 could inactivate 99.9% of 19 1 aerosolized H1N1 influenza virus with a low dose of 2 mJ/cm 2 9 . Another study simulated 2 irradiation for different UV fluences; continuous and intermittent irradiation had no differing 3 effects on SARS CoV2 10 . 4

Thus, 222-nm UV light irradiation is safe; it neither induces skin cancer nor corneal damage in 5 animal or human skin studies. The bactericidal effect and killing of coronaviruses have been 6 tested successfully in safety fluences. The maximum safety fluence was 500 mJ/cm 2 2,7 . The 7 limitation of the study was that the contaminated location could not be detected immediately 8 before the SARS-CoV-2 RT-PCR results are reported. 9

In conclusion, 222-nm UVC light irradiation in a hospital ward environment contaminated with 10 SARS CoV-2 is effective, with a fluence of 81mJ/cm 2 (2 cm in length, 15 s). Further design of 11 222-nm UVC equipment would aid in regular environmental disinfection procedures during the 12 pandemic. Environmental sodium hypochlorite cleaning and patients wearing masks effectively prevent 3 nosocomial infections in healthcare workers (HCWs) 1 . However, sodium hypochlorite cleaning 4 still needs HCWs to enter the contaminated room, which posesa risk of nosocomial infection 5 and could be resolved by automated disinfection such as harmless ultraviolet C (UVC). The 6 krypton-chlorine (Kr-Cl) excimer lamp produces 222-nm UVC irradiation, and the highest 7 exposure is 500 mJ/cm 2 , which is safe in human skin models 2 . This study aimed to use a Kr-Cl 8 excimer lamp to reproduce the viral inactive effect on SARS-CoV-2 in hospital-contaminated 9 environments. 10 1 at 27mJ/cm2 after 5 s irradiation in a single room with a fixed length of 2 cm with stabilized 2 UV radiation intensity. For the purpose of the dosage-related cleaning effect, the irradiation 3 times were 5, 10, 15, 20 s. The fluences were 27, 54, 81, 108 mJ/cm 2 . Environmental samples 4

were collected again after radiation. 5 6

Continuous data are expressed as the mean ± standard error. Categorical data are expressed as 8 frequencies and percentages. The chi-square test was used to compare categorical variables 9 between the different UVC irradiation dosages. The linear trend was also tested using the chi-10 square test for UVC irradiation of the dose effect on SARS-CoV-2. The data were analyzed 11 using SPSS (version 24.0; IBM Corp., Armonk, NY, USA), and a p-value of <0.05 was 12 considered statistically significant. 13

Forty-eight environmental samples were collected. The total contamination rate was 33.3% (Fig.  2   S1 and Supplementary document). 3

To estimate the proper irradiation dosage of 222-nm UVC, a series of studies were conducted 4 to test its dose-related effect on SARS-CoV-2 contaminated environments. In the first survey, 5 four locations in each of the three isolation wards were selected for environmental sampling 6 before irradiation (Table 1) . Before irradiation, three (25.0%) were positively contaminated. 7 SARS-CoV-2 was completely inactivated after 15 s of 222-nm UVC irradiation. However, the 8 contamination was still present in three (25.0%) after 5 s of irradiation, and one (8.3%) after 10 9 s of irradiation, although the decrease was not statistically significant. The separate E and N 10 genes also decreased after irradiation, although this was not statistically significant. The internal 11 control also decreased slowly from 58.3% before the irradiation to 41.7%, 41.7%, and 25.0% 12 after 5, 10, and 15 s, respectively (p=0.433). 13

To determine the optimal UVC irradiation dose (fluence) for SARS-CoV-2 environmental 14 disinfection, repeated studies on the dose effect of UVC irradiation were conducted for 5-20 s 15 on the second-day survey of regular patient activity (Table 1) . SARS-CoV-2 was completely 16 inactivated after 15 s of 222-nm UVC irradiation. The positive contamination rates were 13/36 17 (36.1%) before irradiation and 3/36 (8.3%), 2/36 (5.6%), 0%, and 0% after 5, 10, 15, and 20 s 18 irradiation, respectively (p<0.001). The separate E and N genes showed the same decreasing 19 1

irradiation. The 15 s in 2 cm length had a fluence of 81 mJ/cm 2 , which was the optimal 222-nm 2 UVC dose. The internal control was the same 13/36 (36.1%) as the contamination rate of SARS-3

CoV-2 and slowly decreased with irradiation to 25.0%, 13.9%, 13.9%, and 11.1% after 5, 10, 4 15, and 20 s of irradiation, respectively (p=0.043). 5 1 Figure S1 . Room layout of the isolation ward. ① Bed rails (rate = 3/7, 42.9%) ② Call bell 2 (rate = 0/3, 0%) ③ Bedside table (rate = 2/5, 40%) ④ Kettle (rate = 1/4, 25%) ⑤ Wardrobe 3 (ratio = 1/3, 33.3%) ⑥ Windowsill (rate = 2/3, 66.7%) ⑦ Door handle (rate = 0/3, 0%) ⑧ 4

Toilet seat (rate = 1/4, 25%) ⑨ Flush button (rate = 0/3, 0%) ⑩ Washbasin (rate = 5/10, 50%) 5 ⑪ Toothbrush and mouth cup (rate = 1/3, 33.3%). Total (rate = 16/48, 33.3%) 

222-nm UVC has potential safety in a clean environment and 17 prevents skin damage compared to 254-nm UVC; however, further studies are needed

222 nm) with low doses of 1.7 and 1.2 mJ/cm 2 could inactivate 99

Masks and closed-loop 2 ventilators prevent environmental contamination by COVID-19 patients in negative-pressure 3 environments

Exposure of Human Skin Models to KrCl Excimer 5

Lamps: The Impact of Optical Filtering (dagger)

Effectiveness 7 of 222-nm ultraviolet light on disinfecting SARS-CoV-2 surface contamination

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

UVC light induces neither DNA damage nor epidermal lesions in mouse skin, even at high 14 doses

term Effects of 222-nm ultraviolet radiation C Sterilizing Lamps on Mice Susceptible to 17

Ultraviolet Radiation

This COVID-19 environmental study was approved by the Institutional Review Board of the 2 Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, on July 28, 2021 (Protocol 3No.: 10-X-101). 4Three patients with SARS CoV-2 infection with a nasal swab reverse transcriptase-polymerase 5 chain reaction (RT-PCR) cycle threshold values (CtV) lower than 25 were selected for the 6 environmental contamination study. Patient 1 was a 64-year-old man, patient 2 was a 45-year-7 old man, and patient 3 was a 37-year-old man. All presented with simple SARS-CoV-2 8 bronchopneumonia with a nasal swab SARS-CoV-2 RT-PCR CtV of 18, 16, and 23, respectively. 9Each patient was informed that they did not need to wear a surgical mask in their isolation room 10 during the study. The environmental study time was on the day after admission and 48 to 72 11 hours. The patient performed the usual daily activity without any environmental cleaning. The 12 most frequently touched surfaces in their single independent ward of the hospital were selected 13 with 12 points. 14 Our preliminary study simulated the 222-nm UVC irradiation effect on the SARS-CoV-2 2 contaminated surfaces of the hospital isolation ward. The effective fluence was 81mJ/cm 2 with 3 an environmental SARS-CoV-2 eradication rate of 100%. 4In traditional disinfection procedures, patients must leave the ward before 254-nm UVC 5 irradiation to prevent the risk of skin cancer and corneal damage. A SARS CoV2 in vitro study 6 showed 1-3 mJ/cm 2 222-nm UV irradiation reduced 88.5% to 99.7% of the SARS CoV2 virus 7 detected as 50% tissue culture infectious dose (TCID 50) 3 . In animal studies, 222-nm UV light 8 did not damage the hairless mouse skin 4 . Another hairless mouse skin study found no damage 9to the skin after 10 days of 450 mJ/cm 2 /day chronic irradiation 5 . The corneas of Sprague Dawley 10 albino rats were not damaged by 222-nm UV light with a high exposure level of 600 mJ/cm 2 . 11In an in vitro study of mammalian skin, 222-nm UV light did not yield UV-associated 12 premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) 4 . The 13 other simulated mice study showed Xpa knockout mice irradiated with a high dose of 222-nm 14