Far-UVC light is a novel disinfection technology, distinct from other forms of ultraviolet light. It is currently being studied and commercially developed for its ability to inactivate pathogens like viruses and bacteria. Its purpose is to neutralize these microorganisms, offering a new approach to environmental decontamination.
Understanding the Science of Far-UVC
The ultraviolet (UV) light spectrum is broadly categorized into UVA, UVB, and UVC, based on their wavelengths. UVC light, ranging from 100 to 280 nanometers (nm), is known for its germicidal properties but is typically blocked by Earth’s atmosphere. Far-UVC light occupies a narrow band within this spectrum, generally between 200-230 nm, with 222 nm being a commonly studied wavelength.
The germicidal mechanism of Far-UVC light involves its energy being absorbed by the molecular structures of microorganisms. This absorption damages their genetic material, DNA or RNA, preventing them from replicating and rendering them inactive. Unlike conventional germicidal UVC at 254 nm, Far-UVC’s shorter wavelength is absorbed more strongly by proteins, which helps explain its unique effects on living tissues.
Safety for Human Exposure
Conventional UVC light, particularly at 254 nm, can be hazardous to humans because its longer wavelength allows it to penetrate deeper into the skin and eyes, potentially leading to cellular damage. This penetration can result in conditions like skin cancer and cataracts with prolonged exposure. Therefore, traditional UVC systems are used in unoccupied spaces or with designs that minimize human exposure.
Far-UVC light, especially at 222 nm, has a reduced potential for harm in occupied spaces due to its shorter wavelength. Its photons are largely absorbed by proteins in the outermost, non-living layer of human skin, the stratum corneum, or by the tear layer on the surface of the eye. This absorption mechanism prevents the light from reaching and damaging living human cells underneath these protective layers. Studies have shown that Far-UVC light does not substantially penetrate the dead cell layer of skin and does not reach germinative cells in the basal layer.
Real-World Applications
Far-UVC light’s ability to provide continuous disinfection in occupied spaces presents a significant advantage over traditional methods. Far-UVC lamps are often integrated into environments as overhead fixtures to continuously reduce airborne pathogens.
Examples of its application include hospitals, where it can be used in operating theaters and waiting rooms to enhance infection control. Public transit systems, such as buses and airplanes, are exploring or implementing Far-UVC to disinfect air and surfaces, potentially reducing disease transmission. Schools and offices represent other public venues where this technology can be deployed to create safer indoor environments by neutralizing airborne viruses and bacteria in real-time.
Efficacy and Current Research
Scientific studies consistently demonstrate Far-UVC’s effectiveness at inactivating a wide range of pathogens. This includes common respiratory viruses like influenza and coronaviruses, such as SARS-CoV-2. Research also shows its ability to neutralize antibiotic-resistant bacteria, often referred to as superbugs, including Methicillin-resistant Staphylococcus aureus (MRSA).
Far-UVC has proven effective at inactivating pathogens on surfaces and in the air. For instance, low doses of 222-nm Far-UVC light, specifically 1.7 mJ/cm² and 1.2 mJ/cm², inactivated 99.9% of aerosolized human coronaviruses HCoV-229E and HCoV-OC43, respectively. Continuous Far-UVC exposure at current regulatory limits could achieve approximately 99.9% viral inactivation in about 25 minutes in occupied public locations. Ongoing research aims to optimize dosage and explore its use against an even broader array of pathogens, positioning Far-UVC as an evolving and promising technology for public health.