Ultraviolet (UV) radiation, specifically the UV-C band, is a germicidal electromagnetic energy. With wavelengths typically ranging from 200 to 280 nanometers, it is used for disinfection. Its aim is to eliminate or inactivate microorganisms, controlling pathogen spread.
How UV Radiation Works
UV-C light disinfects by directly impacting the genetic material of microorganisms. When bacteria, viruses, molds, or spores are exposed to UV-C radiation, the high-energy photons are absorbed by their DNA and RNA. This absorption forms pyrimidine dimers in the nucleic acids.
These dimers disrupt the DNA or RNA structure, preventing replication and rendering them inactive and unable to cause infection. Unlike chemical disinfection methods, UV-C operates through a physical process, without introducing any chemical compounds into the treated area.
Appropriate Uses for UV Sterilization
UV-C radiation is used in various settings for disinfection, particularly where direct exposure to the light can be ensured. One significant application is in air disinfection, where UV-C lamps are integrated into HVAC systems or placed in upper room fixtures to continuously clean circulating air. This method helps reduce airborne pathogens in spaces like cleanrooms, hospitals, and public venues.
Water purification also benefits from UV-C technology, offering a chemical-free way to inactivate microbes in drinking water, wastewater treatment facilities, and even aquariums. UV sterilizers in water systems expose water to UV-C light as it flows through a chamber, inactivating microorganisms like bacteria, viruses, and parasites.
Surface disinfection is another common use, especially for non-porous and high-touch surfaces. Laboratory equipment, medical instruments (after cleaning), personal items like phones and keys, and surfaces in healthcare or public transportation can be disinfected. For effective surface disinfection, direct exposure to the UV light is necessary, along with adequate exposure time. Surfaces must also be pre-cleaned to remove any physical debris that could shield microbes.
When UV Sterilization Is Not Effective
Despite its benefits, UV-C sterilization has limitations. One primary constraint is its lack of penetration; UV-C light cannot pass through opaque solids, liquids (like contents inside a sealed bottle), or packaging materials. Only surfaces directly exposed to the light are disinfected, leaving shadowed areas or internal components unaffected.
Porous or rough materials, including fabrics, wood, carpets, or even visibly dirty surfaces, pose another challenge for UV-C disinfection. These materials can shield microorganisms from the UV light, or absorb the radiation, leading to incomplete or ineffective disinfection. UV-C inactivates microbes but does not physically clean surfaces; it does not remove dirt, dust, or organic matter. Therefore, pre-cleaning is consistently required to ensure the UV-C light can reach the target microorganisms.
Direct exposure to UV-C light is harmful to human skin and eyes, causing damage such as DNA lesions and changes to skin cells. This necessitates strict safety protocols, making it unsuitable for direct application on people or in occupied spaces without proper shielding or automated systems that operate when no one is present. Additionally, the effectiveness of UV-C diminishes with increased distance from the light source, and specific intensity and exposure times are required for adequate disinfection.