Ultraviolet germicidal efficacy as a function of pulsed radiation parameters studied by spore film dosimetry

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 178; pp. 69 - 75
• Main Authors: Bauer, Stefan, Holtschmidt, Hans, Ott, Günter
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 01.01.2018; Elsevier BV
• Subjects: Analysis; Biological effects; Biological materials; Broadband; Disinfection; Disinfection & disinfectants; Dosimeters; Dosimetry; Exposure; Germicidal efficacy; Incoherent UV radiation; Irradiance; Lasers; Parameters; Pulse duration; Pulse parameter; Pulse repetition frequency; Pulsed radiation; Pulsed ultraviolet radiation; Radiation sources; Spore film; Spores; Ultraviolet radiation; Disinfection; Germicidal efficacy; Spore film; Pulse parameter; Incoherent UV radiation; Pulsed ultraviolet radiation
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2017.10.027

Disinfection by pulsed ultraviolet (UV) radiation is a commonly used method, e.g. in industry or medicine and can be carried out either with lasers or broadband UV radiation sources. Detrimental effects to biological materials depending on parameters such as pulse duration τ or pulse repetition frequency fp are well-understood for pulsed coherent UV radiation, however, relatively little is known for its incoherent variant. Therefore, within this work, it is the first time that disinfection rates of pulsed and continuous (cw) incoherent UV radiation studied by means of spore film dosimetry are presented, compared with each other, and in a second step further investigated regarding two pulse parameters. After analyzing the dynamic range of the Bacillus subtilis spore films with variable cw radiant exposures H=5–100Jm−2 a validation of the Bunsen-Roscoe law revealed its restricted applicability and a 28% enhanced detrimental effect of pulsed compared to cw incoherent UV radiation. A radiant exposure H=50Jm−2 and an irradiance E=0.5Wm−2 were found to be suitable parameters for an analysis of the disinfection rate as a function of τ=0.5–10ms and fp=25–500Hz unveiling that shorter pulses and lower frequencies inactivate more spores. Finally, the number of applied pulses as well as the experiment time were considered with regard to spore film disinfection. [Display omitted] •Disinfection rates of incoherent UV radiation were studied by spore film dosimetry.•The Bunsen-Roscoe law is restricted to a certain irradiance-exposure time-regime.•Pulsed compared to cw irradiation yields a 28% enhanced germicidal efficacy.•Shorter pulses and higher pulse repetition frequencies inactivate more spores.