Ultraviolet germicidal irradiation disinfection of Stachybotrys chartarum

Abstract

The ultraviolet germicidal irradiation (UVGI) dose necessary to inactivate fungal spores on an agar surface and the efficacy of UVGI were determined for cultures of Stachybotrys chartarum (ATCC 208877). This study employed a UVGI testing unit consisting of four chambers with a 9-W, Phillips, low pressure, mercury UVGI lamp in each chamber. The testing unit's apertures were adjusted to provide 50, 100, 150, and 200 microW/cm2 of uniform flux to the Petri dish surfaces, resulting in a total UVGI surface dose ranging from 12 to 144 mJ/cm2. The UVGI dose necessary to inactivate 90% of the S. chartarum was greater than the maximum dose of 144 mJ/cm2 evaluated in this study. While UVGI has been used to inactivate several strains of culturable fungal spores, S. chartarum was not susceptible to an appropriate dose of UVGI. The results of this study may not correlate directly to the effect of UVGI on airborne fungal spores. However, they indicate that current technology may not be efficacious as a supplement to ventilation unless it can provide higher doses of UVGI to kill spores, such as S. chartarum, traveling through the irradiated zone.

The effect of indoor daylight spectrum and intensity on viability of indoor pathogens on different surface materials

“…We also did not detect any significant indoor daylight effects on S. chartarum , which is in line with previous findings that S. chartarum has high light-resistance. A study by Green et.al (2005) found that ultraviolet germicidal irradiation (UVGI) at 265nm (144mJ cm −2 ) was not efficient to inactivate 90% of the S. chartarum spores 59 . It should note that UVGI emits the highest energy among the UV spectrum, which is much stronger than visible blue light 59 .…”

“…A study by Green et.al (2005) found that ultraviolet germicidal irradiation (UVGI) at 265nm (144mJ cm −2 ) was not efficient to inactivate 90% of the S. chartarum spores 59 . It should note that UVGI emits the highest energy among the UV spectrum, which is much stronger than visible blue light 59 . Therefore, it is not surprising that indoor daylight used in this study was not efficient in reducing the viability of S. chartarum .…”

The effect of indoor daylight spectrum and intensity on viability of indoor pathogens on different surface materials

“…55 No significant indoor daylight effects were detected on S. chartarum, which is in line with previous findings that S. chartarum has high light resistance. A study by Green et al (2005) found that UV germicidal irradiation (UVGI) at 265 nm (144 mJ cm −2 ) was not efficient to inactivate 90% of the S. chartarum spores. 56 It should be noted that UVGI emits the highest energy among the UV spectrum, which is much stronger than visible blue light.…”

“…A study by Green et al (2005) found that UV germicidal irradiation (UVGI) at 265 nm (144 mJ cm −2 ) was not efficient to inactivate 90% of the S. chartarum spores. 56 It should be noted that UVGI emits the highest energy among the UV spectrum, which is much stronger than visible blue light. 56 Therefore, it is not surprising that indoor daylight used in this study was not efficient in reducing the viability of S. chartarum.…”

“…56 It should be noted that UVGI emits the highest energy among the UV spectrum, which is much stronger than visible blue light. 56 Therefore, it is not surprising that indoor daylight used in this study was not efficient in reducing the viability of S. chartarum.…”