May. 13, 2024
The disinfection and sterilization of transmission routes of pathogens are key infection control procedures. These measures kill any microbes present, thereby making the environment cleaner and safer for human use and occupancy. One of the methods that has been in use for over a century is ultraviolet (UV) light sterilization.
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The use of UV light as a method to sterilize areas and reduce the transmission of pathogens was first proposed in 1878 by Arthur Downes and Thomas P. Blunt. The first recorded use of UV light as a disinfection agent was reported in Marseilles, France, in 1910, to sterilize drinking water in a prototype plant.
By the 1950s, UV water treatment was in use in Switzerland and Austria. By 1985, there were 1,500 UV water treatment plants in operation in Europe. By 2001, this number rose to 6,000 UV water treatment plants that were in use in Europe.
Today, UV light is widely used in hospitals as a sterilization agent for rooms and surfaces. As the use of UV light has become increasingly popular for disinfection purposes, ultraviolet germicidal irradiation (UVGI) systems have also become much cheaper.
The ongoing coronavirus disease 2019 (COVID-19) pandemic has renewed interest in using UV light for sterilizing rooms and air filtration systems.
UV light is electromagnetic radiation that has a wavelength longer than X-rays but shorter than visible light. UV light is categorized into different wavelengths, including UV-C, which is short-wavelength UV light often referred to as "germicidal" UV.
UV-C operates between wavelengths of 200 and 300 nanometers (nm), where nucleic acids in a microbe are disrupted. The nucleic acids absorb the UV-C light, resulting in pyrimidine dimers that disrupt the nucleic acids' ability to replicate or express essential proteins. This leads to cell death in bacteria and inactivation in viruses.
Germicidal UV lamps are the primary method of application. There are several different types of UV lamps currently in use, including:
UVGI systems can be installed in enclosed spaces where the constant flow of air or water ensures high levels of exposure. The effectiveness depends on the quality and type of equipment used, the duration of exposure, wavelength and intensity of UV, the presence of protective particles, and the microorganism's ability to withstand UV light. Even something as simple as dust on the bulb can affect the efficacy, so equipment must be regularly cleaned and replaced to ensure its effectiveness.
UV sterilization processes have several advantages and disadvantages. In the case of water sterilization, UV provides superior disinfection without the use of chlorine; however, UVGI-treated water is prone to reinfection. There are safety concerns, as UV light is harmful to most living organisms, and unwanted exposure can cause sunburns and increased risk of certain cancers in humans. Other safety concerns include the risk of vision impairment.
Microorganisms such as fungal spores, mycobacteria, and environmental organisms are harder to kill with UVGI systems compared to bacteria and viruses. However, UVGI systems that emit high doses of UV light can still remove fungal contaminants from air conditioning systems. Historically, UV light has been used to kill tuberculosis and to prevent hospital-based outbreaks of drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA).
Since early 2020, COVID-19, caused by the highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected over 203 million people worldwide and caused the deaths of more than 4.3 million. Mandated mask-wearing and social distancing measures have been implemented in most countries worldwide to mitigate the spread of SARS-CoV-2. However, several other methods have been employed to gain control of the pandemic.
UV disinfection and sterilization measures have received renewed interest since the pandemic's start. UV-C and, to a lesser extent, UV-A, and UV-B radiation have been shown to inactivate SARS-CoV-2. However, there remains insufficient evidence on the effectiveness of UV-C radiation in mitigating the spread of SARS-CoV-2 due to the limited amount of published data on the duration, wavelength, and dose of UV radiation needed to inactivate SARS-CoV-2.
SARS-CoV-2 primarily spreads through respiratory droplets expelled from symptomatic or asymptomatic carriers. This has led to a burgeoning market in UV-C sterilization equipment, including sanitizing tunnels, UV-C air conditioning and purifying systems, and hand dryers with UV lamps.
Despite their potential utility, these systems do not replace proven controls such as mask-wearing and social distancing. UV-C systems can act as an extra layer of defense against SARS-CoV-2.
UV light is an effective sterilization measure against a wide range of different microorganisms present within the environment. The use of UV sterilizing equipment is becoming more widespread, particularly in response to the ongoing COVID-19 pandemic. It is likely that this industry will continue to grow over the coming years.
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