UVC light is a specific type of ultraviolet radiation, an invisible form of electromagnetic energy that exists beyond the violet end of the visible light spectrum. UVC wavelengths are imperceptible to the human eye, yet they carry sufficient energy for various applications.
UVC in the Electromagnetic Spectrum
The electromagnetic spectrum encompasses a wide range of radiation, and ultraviolet (UV) light occupies a segment shorter in wavelength than visible light but longer than X-rays. Within the UV spectrum, UVC light is characterized by its shortest wavelengths, ranging from 100 to 280 nanometers. This range places UVC at the higher energy end of the UV spectrum compared to UVA and UVB.
Solar UVC radiation is almost entirely absorbed by Earth’s atmosphere, primarily by the ozone layer and other atmospheric gases, preventing it from reaching the surface. This atmospheric absorption means that any UVC light used for practical purposes must be generated by artificial sources, such as specialized lamps or UVC LEDs. These artificial sources can be engineered to emit specific UVC wavelengths, enabling their controlled application.
How UVC Inactivates Microorganisms
UVC light inactivates microorganisms, including bacteria, viruses, and fungi, by damaging their genetic material. The specific wavelengths of UVC are readily absorbed by the nucleic acids—DNA and RNA—within these microbes. This absorption of high-energy UVC photons causes photochemical reactions within the DNA or RNA strands.
These reactions lead to the formation of molecular lesions known as pyrimidine dimers. Pyrimidine dimers are covalent bonds that form between adjacent pyrimidine bases on the same strand of the DNA or RNA helix. The formation of these dimers distorts the double helix structure, which then prevents the microorganisms’ genetic material from accurately replicating or transcribing. Without the ability to copy their DNA or RNA, the microbes cannot reproduce, rendering them unable to cause infection or spread.
Practical Uses of UVC Light
The germicidal properties of UVC light have led to its widespread adoption for disinfection and purification. In air purification systems, UVC lamps are integrated into HVAC (heating, ventilation, and air conditioning) units or standalone air purifiers to treat airborne microorganisms. As air passes through these systems, the UVC radiation inactivates bacteria, viruses, and molds, improving indoor air quality and reducing the spread of airborne pathogens.
UVC is also employed in water treatment processes, disinfecting drinking water, wastewater, and even pool water. This method offers a chemical-free way to eliminate pathogens, preventing the formation of harmful by-products associated with chemical disinfection. For surface disinfection, UVC light is utilized in hospitals, laboratories, and public spaces to sanitize equipment and high-touch surfaces. Robotic UVC disinfection systems are used for large-scale area sanitization, particularly when spaces are unoccupied.
Medical facilities use UVC light for sterilizing surgical instruments and other medical equipment, ensuring they are free from harmful microorganisms. Beyond healthcare, UVC technology finds application in the food processing industry to disinfect food surfaces and packaging, which can help extend shelf life and enhance food safety. UVC light plays a role in creating cleaner and safer environments across multiple sectors.
Safe Interaction with UVC
Direct exposure to UVC light can pose health risks to humans, primarily affecting the skin and eyes. The high energy of UVC radiation can cause severe sunburn-like effects on the skin. This damage occurs rapidly and can be painful, though it is temporary.
The eyes are particularly vulnerable to UVC exposure, which can lead to a painful condition called photokeratitis, sometimes referred to as “welder’s flash”. Symptoms, such as a feeling of sand in the eyes, appear several hours after exposure and include extreme discomfort and aversion to light. While these eye injuries are temporary and heal within days, prolonged or intense exposure can cause more severe damage.
To interact safely with UVC light, direct exposure to skin and eyes must be avoided. UVC systems are often designed for use in enclosed environments, such as within HVAC ducts or water treatment chambers, or in unoccupied spaces. When personnel must be present during operation, proper shielding and personal protective equipment, including UV-blocking face shields, gloves, and long-sleeved clothing, are necessary to prevent harm.