Effect of UV Light on Mildew


Molds and mildew are part of the fungi family, a microorganism which forms colonies in damp conditions. Typically this occurs when wood (such as walls), furniture or other organic materials are exposed to water damage. One mechanism to control fungal colonies involves exposing them to ultraviolet light, which effectively kills molds and other fungi.


  • Fungi are multicellular organisms which include mildew, molds and mushrooms. As with all fungi, mildew grows on organic material in conditions of humidity and within a certain temperature range. Fungi reproduce by spreading airborne spores that can establish new colonies elsewhere. Extremes of cold and heat can kill mildew, but fungal spores can tolerate these conditions and remain dormant until the environment is ideal for growth.

Mildew Growth

  • Though part of the fungi family, "mildew" refers to a mold which is growing on fabric or any other covering made of organic matter. As with all fungi, mildew does not produce food by photosynthesis; it extrudes roots, or "hyphae" into the material it is growing in. The hyphae secrete enzymes which breaks down organic matter into compounds the mildew fungus can absorb for nutrition. This leads to damage on whatever the mildew colony is growing on. Optimal conditions for mildew growth are 60 percent humidity in the environment, with a temperature of between 10 to 32 degrees Celsius.

Ultra-Violet Light

  • Ultraviolet or "UV" light is a wavelength of radiation. It is part of the electromagnetic spectrum, which includes microwaves, visible light and infrared radiation. Each wavelength of radiation is composed of an electric and magnetic field, with energy moving back and forth between them. All radiation vibrates at a particular frequency and moves at the speed of light.

How UV Light Kills Mildew

  • Ultraviolet light has energy characteristics which makes it effective in destroying microorganisms such as fungi. When exposed to UV light, the genetic material in cells is damaged as chemical bonds are severed within the DNA structure. Prolonged exposure to UV light inflicts more damage to the point where the DNA cannot be repaired and cells die as a result. UV light is used to control fungal growths in homes after water damage and to treat items infested with mold, such as books and museum exhibits.

Health Risks of Fungi

  • Health hazards associated with mold and mildew are respiratory; this is due to spores being released by fungi into the air. If inhaled, spores can irritate tissue in the lungs or upper respiratory tract, and trigger asthmatic or other severe allergic reactions. Spore presence in air is compounded if there is poor ventilation where molds are present. Certain molds which grow in foods produce mycotoxins which are poisonous when ingested. Other fungi such as mushrooms are also toxic when eaten.

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  • Photo Credit mould image by dinostock from Fotolia.com
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