Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a serious threat to human health worldwide. The inactivation of SARS-CoV-2 on object surfaces and in the indoor air might help to halt the COVID-19 pandemic. Far-ultraviolet light (UVC) disinfection has been proven to be highly effective against viruses and bacteria. To understand the wavelength and duration of UVC radiation required for SARS-CoV-2 inactivation, we examined the efficacy of UVC light prototype devices with the wavelengths of 275, 254, and 222 nm. The disinfection effectiveness was determined by cell-based assays including the median tissue culture infectious dose (TCID50) and an immunofluorescent assay on African green monkey kidney epithelial Vero E6 cells. Among the three prototypes, the UVC LED (275 nm) had the best virucidal activity with a log-reduction value (LRV) >6 after 10 s of exposure. The mercury lamp (254 nm) reached similar virucidal activity after 20 s of exposure. However, the excimer lamp (222 nm) showed limited anti-SARS-CoV-2 activity with a LRV < 2 after 40 s of exposure. Overall, in comparison, the UVC LED (275 nm) exhibited superior SARS-CoV-2 disinfection activity than the mercury lamp (254 nm) and the excimer lamp (222 nm).

Indoor recirculating aquaculture systems make light control possible and enable the usage of specific coloured lights to promote the growth and immunity of aquaculture species. Five different LED wavelengths (white light, red light [622 nm], green light [517 nm], blue light [467 nm], and dark) were used in this study to evaluate growth and immunity in the glass eel stage of two high-valued anguillid species, Japanese eel ( Anguilla japonica ) and giant mottled eel ( A. marmorata ). There were no significant differences in growth of the Japanese eel among the groups after ­12 weeks of feeding (P > 0.05); the survival rate of each group was over 95%. The giant mottled eel showed better growth in total length and body weight in the red light and dark groups (P < 0.05). Expression levels of immune-related genes were not significantly different between each group of the Japanese eel and the giant mottled eel (P > 0.05). The growth of the Japanese glass eel was not significantly sensitive to different LED wavelengths, while the giant mottled glass eel showed better growth under red light and dark environments. Neither eel species showed significant differences in innate immunity under different LED wavelengths.