Abstract
BackgroundPulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and also have high potential for use in a wide range of microbial decontamination applications. The acaricidal effect of an experimental UV-C irradiation device was assessed using female adults and eggs of a model organism, the two-spotted spider mite Tetranychus urticae.MethodsUV-C light was generated by a pulsed krypton fluoride excimer laser operating at 248-nm emission wavelength. The pulse energy and pulse repetition rate were 5 mJ and up to 100 Hz, respectively. The distance from the light source to the target was 150 mm; the target surface area was 2.16 cm2. The exposure time for the mites and fresh eggs varied from 1 to 4 min at 5–300 mW, which corresponded to UV doses of 5–80 kJ/m2. Post-irradiation acaricidal effects (mite mortality) were assessed immediately and also measured at 24 h. The effects of UV-C irradiation on the hatchability of eggs were observed daily for up to 12 days post-irradiation.ResultsThe mortality of mites at 5 and 40 kJ/m2 was 26% and 92%, respectively. Mite mortality reached 98% at 80 kJ/m2. The effect of exposure duration on mortality was minimal. The effect of irradiation on egg hatchability was even more significant than that on adult mite mortality, i.e. about 100% egg mortality at an accumulated dose of as little as 5 kJ/m2 for each exposure time.ConclusionsA high rate of mite mortality and lethal egg damage were observed after less than 1 min of exposure to 5 mJ UV-C pulsed irradiation at 60 Hz. Pending further developments (such as beam steering, beam shaping and miniaturisation) and feasibility studies (such as testing with mites in real-life situations), the reported results and characteristics of the UV-C generator (modulation of energy output and adaptability to varying spot sizes) open up the use of this technology for a vast field of acaricidal applications that require long-range radiation.Graphical
Highlights
Pulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and have high potential for use in a wide range of microbial decontamination applications
The effect of UV-C irradiation of the adult female mites was quantified after 24 h, and showed that they were significantly impacted by the amount of energy delivered
The results showed that a reasonably high level of mortality could already be achieved after less than 1 min of exposure to the UV-C radiation produced by the laser beam
Summary
Pulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and have high potential for use in a wide range of microbial decontamination applications. Non-ionising UV-C irradiation, alone or in combination with other cleaning and disinfection methods, is a physical technology that is increasingly used for a wide range of applications. It is used in the food industry and for food safety [7, 8], in agriculture [9], for water decontamination [10, 11], for indoor air purification and surface cleaning [12,13,14], in healthcare environments [15,16,17,18,19], and for the treatment of personal protective equipment [20]. The latter application is under particular scrutiny at the moment in the context of the coronavirus disease pandemic and related critical shortages in the supply chain of personal protective equipment [21, 22]
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