Ultraviolet-C (UV-C) is a specific type of ultraviolet light known for its ability to inactivate microorganisms. It has a germicidal property, meaning it can eliminate or inactivate pathogens.
Understanding UV-C Radiation
UV-C radiation is a segment of the electromagnetic spectrum. The wavelength of UV-C light ranges from 200 to 280 nanometers (nm). This is the shortest wavelength among the ultraviolet categories, which also include UV-A and UV-B.
UV-A light has the longest wavelength, between 315 nm and 400 nm, and is closest to visible light. UV-B light falls in the medium wavelength range, from 280 nm to 315 nm. While the sun emits all three types of UV radiation, nearly all naturally occurring UV-C rays are absorbed by the Earth’s ozone layer and atmosphere, preventing them from reaching the surface. Therefore, human exposure to UV-C primarily comes from artificial sources.
How UV-C Disinfects
UV-C light inactivates microorganisms by damaging their genetic material, specifically their DNA and RNA. When exposed to UV-C rays, the light is absorbed by the nucleic acids within their cells. This absorption causes molecular damage, disrupting the bonds within the DNA structure.
The damage leads to the formation of pyrimidine dimers, which are abnormal bonds between adjacent DNA building blocks. These dimers prevent the DNA or RNA from being accurately copied or used to produce essential proteins. As a result, the microorganism cannot replicate or carry out its functions, leading to its inactivation or death. The most effective wavelength for this germicidal process is around 254 nm, though the entire UV-C range exhibits germicidal properties.
Common Applications of UV-C
UV-C technology is applied in various settings for disinfection. In air purification, UV-C lamps are integrated into Heating, Ventilation, and Air Conditioning (HVAC) systems and portable air purifiers to disinfect circulating air. This helps reduce airborne pathogens like viruses, bacteria, and mold spores.
For water treatment, UV-C systems disinfect drinking water and wastewater by inactivating waterborne microorganisms without chemicals. This method is effective against pathogens such as E. coli and Cryptosporidium. Surface disinfection is another application, where UV-C devices are employed in hospitals, laboratories, and public transport to sterilize surfaces. They are also used in homes to disinfect everyday items and surfaces.
Safety and Precautions with UV-C
Exposure to UV-C radiation can pose hazards to human health, particularly to the skin and eyes. Direct exposure to UV-C can cause skin burns. For the eyes, it can lead to photokeratitis, a painful inflammation of the cornea, and contribute to the development of cataracts over time.
It is important to never look directly at UV-C light sources or expose bare skin to them. Many UV-C disinfection systems are designed as enclosed units to prevent human exposure during operation. When handling UV-C devices or working in areas where UV-C is in use, appropriate personal protective equipment, such as UV-C blocking eyewear and protective clothing, should be worn. Adequate ventilation is also recommended in areas where UV-C is actively disinfecting, especially for systems that may produce ozone as a byproduct.