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Background Since the outbreak of Sars-CoV-2 public health measures have been adopted globally, most notably the use of face masks has become essential and often mandatory. As a result, about 3.4 billion single-use face masks are estimated to be discarded daily worldwide. Due to waste mismanagement, the COVID-19 pandemic is severely impacting the environment, the ecosystem and therefore human health. We aimed to assess if UV-C light is an efficient tool for proper mask disinfection, to guarantee their safe reuse and reduce their waste. Methods In October 2020 we conducted a cross sectional study on KN95 masks. Various operators wore the masks during their shift in the laboratory for 8, 16 and 24h. Contact plates were used to measure microbial contamination on both surfaces of the masks at time T(0). Then, masks were placed into a UV-C box (volume of 0.012 m3, 40 UVC LED at 270nm at 3mW) for a treatment of 3 minutes. We repeated the sampling at time T(1). We incubated all plates at 36 °C and read them after 48h. We performed descriptive and inferential (Wilcoxon matched pair test) analysis with Stata. Significance level was set at p < 0.05. Results We always observed greater contamination on internal surfaces than external ones. At T(0) the medians of CFU on samples of internal surface were 212.7 (CI 95% 0-480.2) at 8h, 311.7 (0-683.1) at 16h and 404.7 (0-736.1) at 24h; at T(1), CFU reduced (p < 0.05) and were respectively 3.2 (0-6.2), 2 (0-5.9) and 50.6 (0-164.7). At T(0) the medians of CFU on external surface were 23.7 (0-48.4), 53.2 (0-143) and 24.3 (0-71.8); at T(1) they respectively reduced (p < 0.05) to 8.7 (0-25.2), 18.2 (0-70), 2.3 (0-6.1). Conclusions Results showed that UV-C is effective in mask disinfection although an uncomplete abatement of the microbial load. It could be due to the limited UV-C dose or to its difficulty to penetrate among the meshes of the mask. Further investigation is needed to find a sustainable solution for mask use. Key messages UV-C seems a valid disinfection tool for used KN95 masks. The development of strategies for proper disinfection of masks should be carried out to guarantee reusability and reduce waste production. [ABSTRACT FROM AUTHOR]

Background: Microbes are less able to develop resistance towards antimicrobial blue light (aBL), at 405nm, towards disinfectants/ antibiotics. In addition, Near UV-A light (nUV) is less harmful to host cell compared to UV-C irradiation. This study aimed to assess the efficiency aBL in reducing microbial growth on surfaces. Methods: This cross-sectional study, run between July-October 2020. Petri dishes were contaminated with P. Aeruginosa, E. Coli, S. Aureus, S. Typhimurium, K. Pneumoniae at a concentration of 1.5x104 CFU/mL and were placed at 2 and 3m of distances from the light source having an irradiance of 967,39 and 497,33 mW/cm2 for 12 hours. The air confined the room was sampled for two weeks with two air samplers (SAS), before and after the exposition to the nUV light source to estimate the reduction of the environmental microbial contamination. The analysis was conducted using Stata software. Final results were expressed as logarithmic reduction mean with 95% confidence interval. Results: The highest microbial reduction was reached 2m directly under the light. Significant (p < 0.05) log-reduction were achieved for S. Typhimurium, 2.93 (IC 2.44-3.40), K.Pneumoniae, 2.30 (IC 2.14-2.46), S.Aureus, 3.98 (IC 3.78- 4.12), E.Coli, 3.83 (IC 3.17-4.50), P. Aeruginosa, 3.86 (IC 3.22- 4.48). At 3m of distance from the light source, it was observed a significant logarithmic reduction for S. Aureus, 3.49 (IC 3.34-3.65), and P. Aeruginosa, 3.80 (IC 3.11-4.47). In the air tests, we observed a mean percentage microbial reduction of about 70% after 12 h of exposure to nUV light. Conclusions: nUV has proven to contrast microbial growth on the plates. It is possible to implement this technology in the environment for controlling microbial presence in ‘‘ad hoc’’ scenario but also in common areas. Mitigating the energy, it is possible to use this technology in presence of persons. Key messages: In this experimental study, near UV-A has proven to be efficient to reduce the microbial growth and to disinfect air and surface. Near UV light (nUV) can be use as an innovative technology for decreasing bacterial contamination, also in presence of people. Background: Microbes are less able to develop resistance towards antimicrobial blue light (aBL), at 405nm, towards disinfectants/ antibiotics. In addition, Near UV-A light (nUV) is less harmful to host cell compared to UV-C irradiation. This study aimed to assess the efficiency aBL in reducing microbial growth on surfaces. Methods: This cross-sectional study, run between July-October 2020. Petri dishes were contaminated with P. Aeruginosa, E. Coli, S. Aureus, S. Typhimurium, K. Pneumoniae at a concentration of 1.5x104 CFU/mL and were placed at 2 and 3m of distances from the light source having an irradiance of 967,39 and 497,33 mW/cm2 for 12 hours. The air confined the room was sampled for two weeks with two air samplers (SAS), before and after the exposition to the nUV light source to estimate the reduction of the environmental microbial contamination. The analysis was conducted using Stata software. Final results were expressed as logarithmic reduction mean with 95% confidence interval. Results: The highest microbial reduction was reached 2m directly under the light. Significant (p < 0.05) log-reduction were achieved for S. Typhimurium, 2.93 (IC 2.44-3.40), K.Pneumoniae, 2.30 (IC 2.14-2.46), S.Aureus, 3.98 (IC 3.78- 4.12), E.Coli, 3.83 (IC 3.17-4.50), P. Aeruginosa, 3.86 (IC 3.22- 4.48). At 3m of distance from the light source, it was observed a significant logarithmic reduction for S. Aureus, 3.49 (IC 3.34-3.65), and P. Aeruginosa, 3.80 (IC 3.11-4.47). In the air tests, we observed a mean percentage microbial reduction of about 70% after 12 h of exposure to nUV light. Conclusions: nUV has proven to contrast microbial growth on the plates. It is possible to implement this technology in the environment for controlling microbial presence in ‘‘ad hoc’’ scenario but also in common areas. Mitigating the energy, it is possible to use this technology in presence of persons. Key messages: In this experimental study, near UV-A has proven to be efficient to reduce the microbial growth and to disinfect air and surface. Near UV light (nUV) can be use as an innovative technology for decreasing bacterial contamination, also in presence of people. [ABSTRACT FROM AUTHOR]

Background: UV-C has proven to be an effective microbiocide method for disinfecting objects in domestic and work environments. Aim of this study was to test the biocidal efficiency of an UVC box on a real video-camera. Methods: In February 2021, a descriptive study on a parallelepipedshaped UVC box, produced by Cartoni S.p.a., was conducted at the University of Siena. The box has 10 UV-C lamps (254nm at 0.9 Watt/each) and all six mirrored reflective walls. It was specifically engineered for disinfecting equipments for film makers. A real professional camera was used to assess the level of disinfection. Contamination was obtained inoculating 1.5x107CFU/mL of S. Aureus ATCC 43300 on five 20 cm2 plastic carriers positioned in five different spots (referred as spots A, B, C, D, E), both directly (spot A), and indirectly (by reflected light, spots B, C, D, E) exposed to a UV-C light source. After a cycle of 3minutes’ exposition to UV-C: all carriers were transferred on empty Petri dishes; 10mL D/E medium was added, transferred into a 50ml Falcon and spun for 40minutes at 4500rpm; the supernatant was then removed and 100 ml of it was incubated into a Petri dish (with a generic growth medium) at 36[C for 48h. The experiment was run in triplicate. The mean logarithmic reduction and its 95% confidence interval were calculated from the replicates data and compared with positive controls (1.5x107CFU/mL). Results: Mean logarithmic reduction compared to positive control was in spot A: 6.33 log10(C.I. 5.90-6.75), spot B: 4.74 log10(C.I. 4.11-5.33), spot C: 4.83 log10(C.I. 4.75-4.91), spot D: 4.89 log10(C.I. 4.12-5.65), spot E: 5.00 log10(C.I. 4.79-5.21). Conclusions: These experiments showed that after 3minutes of UV-C exposure there is a significant reduction in the bacterial load, 4 to 6 log10 (99.99% to 99.9999% reduction), on the carriers. The results also highlight the ability of the UV-C box to disinfect all infected spots, including those irradiated by reflected light. [ABSTRACT FROM AUTHOR]