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Intermittent low-dose far-UVC irradiation inhibits growth of common mold below threshold limit value

Summary

This study shows that a special type of ultraviolet light called far-UVC, operating at 222 nanometers, can effectively stop common household mold from growing. The light works best when it cycles on and off throughout the day, and importantly, the doses used are safe enough for people to be in the same room. This technology could help prevent mold problems in homes and hospitals without requiring chemicals or forcing people to leave the area.

Background

Mold infestations in buildings pose significant health challenges, triggering asthma and allergies in immunocompetent individuals and life-threatening infections in immunocompromised patients. Far-UVC light at 222 nm can inactivate microorganisms while remaining safe for human exposure, offering potential for use in occupied spaces.

Objective

To investigate the inhibitory efficacy of intermittent low-dose far-UVC light at 222 nm on the growth of Penicillium candidum, a common mold-producing fungus, when delivered in on-off duty cycles at doses below the Threshold Limit Value of 23 mJ/cm².

Results

Far-UVC light significantly inhibited both vertical and horizontal growth of P. candidum in both experimental setups. At 25 mJ/cm² from airborne spores, only minor growth appeared on one-third of plates with <1% coverage. In seeded spore experiments, 20 mJ/cm² prevented all growth, while 10 and 15 mJ/cm² doses showed minimal diameter increases of 0.53 and 0.25 mm respectively compared to 3.28 mm in controls.

Conclusion

Intermittent cycling doses of far-UVC light below the current TLV of 23 mJ/cm² effectively inhibit P. candidum growth, suggesting far-UVC technology has potential to improve indoor air quality and prevent mold infestations while remaining safe for human presence.
  • Published in:PLoS ONE,
  • Study Type:Experimental Laboratory Study,
  • Source: 10.1371/journal.pone.0299421; PMID: 38954713
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