Science of UVC
Safer Planet Advisor, Christian Sandrock MD is an Infectious Diseases, Pulmonary, and Critical Care expert with over 2 decades of experience in respiratory and emerging infectious diseases. His clinical practice and research have focused on emerging infectious diseases at the animal and human interface, particularly respiratory infections such as avian influenza, SARS, Ebola, Mycobacterial disease, and other pandemic agents such as coronaviruses. Dr. Sandrock currently teaches at U.C. Davis and is an advisor to Safer Planet.
The use of light and UV irradiation to suppress growth of micro-organisms has been known for at least 175 years. UV irradiation is commonly used as a disinfectant for water treatment as well as for air purification. The increase in food borne illness, drug resistant organisms, and the emergence of novel virus (SARS, H1N1) as well as bioterrorism were all red flags for the need of alternative technologies to fight harmful micro-organisms. The COVID-19 global pandemic has brought an even higher sense of urgency for the need for additional tools to make our environment safer. Depending on the pathogen, surface (contact) or air may be the primary mode of transmission, however each mechanism may contribute to a spread.
In simple terms, defensive and preventive strategies against pathogens and making our environment safer are driven by 3 factors as shown below.
The type of pathogen (viruses, bacteria, fungi, protozoa), the mode of transmission (directly or in-directly, e.g., fomites, airborne, vector borne) and pathogen load (quantity and replication time) are major considerations in defining a preventive strategy. Due to this complexity, often times are no simple preventive solutions are available. Every known and proven recommended practice such as wearing of masks and/or other PPE, social distancing, avoiding crowds (particularly indoors), and frequently washing hands, all contribute to reduction in probability of transmission. Generally, it will be good practice to deactivate these pathogens, regardless of the transmission mechanism, before they enter the environment and thus reduce the risk of entering our body.
One technology, ultraviolet germicidal irradiation (UVGI), and specifically UVC, has gained significant momentum in utilization as a sanitizing tool. Broadly speaking, UV light is defined by the wavelength with 4 categories:
Vacuum UV in the range of 100-200nm
UVC in the range of 200-280 nm
UVB in the range of 280-315 nm
UVA in the range of 315 -400 nm
Numerous publications point to the efficacy of UVC deactivating microbes. Simply stated, UVC will damage nucleic acid in the microorganisms as the wavelengths are absorbed by the DNA or RNA, rendering the microbes unable to reproduce. The effectiveness of UVC varies by the type of microbe, wavelength, and fluence (intensity and duration) of the UVC exposure. Proper and safe usage of UVGI can be an effective germicidal tool. Use this link, for more on germicidal efficacy of UVC and published references.
The application of UV technology for environmental decontamination in the healthcare industry is well known. However, the use of UV within the healthcare setting is still at its infancy in understanding the potential and safe operation of UV radiation. For over 20 years other industries such as semiconductor device and equipment manufacturing have safely deployed UV technology to enable next-generation technology nodes in equipment such as photolithography, critical feature measurement and for defect inspection on silicon wafers.
It’s possible that collaboration with other industries can accelerate research and development of new tools and procedures that will benefit healthcare and the public in fight against contagions.
Christian Sandrock MD