Bactericidal Effect and Safety Evaluation of 222 nm Far-ultraviolet
[Objective]The spread of pathogenic bacteria in the environment was an urgent problem to be solved in the prevention and control of current diseases.Traditional ultraviolet(254 nm)was the main mode of environmental disinfection at present,which was limited due to its irreversible damage to the immune system,skin and eyes,so exploring an uninterrupted,safe and effective means of disinfection was a promising study.[Method]A poor site was selected to investigate the effect of uninterrupted irradiation with 222 nm far-ultraviolet light for 8 h on the elimination of pathogenic bacteria in the environment,in which the negative control group was not treated,the positive control group was placed openly,and the far-ultraviolet group was irradiated with the far-ultraviolet light from a distance of 30 cm at the same time as it was placed openly.The common clinical pathogenic bacteria(Staphylococcus aureus,Bacillus subtilis,Pseudomonas aeruginosa and Escherichia coli)were coated with continuous irradiation for 30 min,and negative and positive control groups were set up,so as to compare the difference between the far-ultraviolet rays and the traditional ultraviolet rays.The surface bactericidal effect of the far-ultraviolet rays on the common pathogenic bacteria was examined by comparing the irradiation distances(20 and 30 cm)and the action times(15,30,45,60,75 and 90 s).Common pathogenic bacteria were inoculated into liquid culture medium to investigate the bactericidal effect of ultraviolet radiation on bacteria in the liquid.After uninterrupted irradiation of mice with 222 nm far-ultraviolet radiation for 8 h,the clinical status,blood routine,and skin histological changes were observed to preliminarily determine the safety of far-ultraviolet radiation on the body.[Result]Compared with the negative control group,a variety of bacteria were observed on the culture medium of the positive control group,while no bacteria were colonized on the culture medium of the far-ultraviolet group.By continuously irradiating with 222 nm far-ultraviolet light for 30 minutes,Staphylococcus aureus,Bacillus subtilis,Pseudomonas aeruginosa,and Escherichia coli could be killed.The bactericidal rate could reach 99.9％after 15 s of irradiation.The bactericidal effect of 222 nm far-ultraviolet light irradiated at a distance of 20 cm was generally better than that irradiated at a distance of 30 cm.In the liquid bactericidal evaluation,the sterilizing effect of far-ultraviolet light was not good.The results of the safety test in mice showed that the uninterrupted irradiation of 222 nm far-ultraviolet light for 8 h had no significant effect on the clinical symptoms,internal organs,blood and skin tissues of the mice,while the traditional ultraviolet light might cause damage to them.[Conclusion]222 nm far-ultraviolet light had a strong bactericidal effect on the surface colonization of common pathogenic bacteria,and the bactericidal rate could be as high as 99.9％in 15 s.The irradiation distance was directly proportional to the bactericidal effect,but the bactericidal effect on the liquid still needed to be improved and upgraded.Moreover,the continuous irradiation for 8 h would not have a significant effect on the clinical status,blood routine and skin histology of mice,and it had a good safety,providing a new solution for the prevention and control of the disease in the environment.
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