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What you need to know about UV disinfection




Often referred to as ultraviolet (UV) light, UV radiation is a type of electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays. UV radiation comes naturally from the sun, but it can also be created by artificial sources.

How UV disinfection works

UV radiation falls into three main categories depending on its wavelength: UVA, UVB and UVC (see the diagram below). The shorter the wavelength, the more energetic is the radiation. UVC, which has the shortest wavelength can act as a disinfectant and has been used in healthcare, food and biotech for over 30 years.


 


UVC “kills” or rather inactivates cells by disrupting their cellular membranes and damaging their DNA or RNA. If cellular processes are disrupted because of DNA damage, the cell cannot carry out its normal functions and can’t reproduce. Microorganisms that can’t reproduce can’t cause diseases. This technology works by line of sight, so the light must reach a surface in order for bacteria or viruses to be deactivated. Environments where design creates obstacles that block the UV light are not as effective. 

UV radiation works by line of sight

Ensuring effective UV disinfection

UV disinfection is controlled by two key parameters: wavelength and total UV exposure (UV dose).

 

The most effective germicidal wavelength occurs at a peak of 265 nm at which DNA absorbs UV the most. Mercury-based lamps operating at low vapor pressure emit UV light at 253.7 nm. UVC LED lamps emit UV light at selectable wavelengths between 255 and 280 nm. PureFize® creates UVC light with a very broad germicidal spectrum with a peak wavelength at 262 nm. The germicidal effectiveness of UVC peaks at about 260-265 nm, which corresponds to the peak of UV absorption by bacterial DNA.* 

* Kowalski, W. "Ultraviolet Germicidal Handbook. UVGI for Air and Surface Disinfection." Springer-Verlag Berlin Heidelberg, 2009, p.17

UV damage and photoreactivation

Some organisms are able to repair the UV damage inflicted to their DNA and start reproducing again. This process is called photoreactivation and may greatly reduce the efficacy of UV disinfection. A number of studies have been performed to investigate this subject and researchers have found that using UV light at a broad range of wavelengths hinders subsequent photoreactivation (1). PureFize, with its broad wavelength spectrum, is designed to deliver enough UV dose to prevent any germ reactivation and regrowth.

 

(1) For example: Oguma K, Katayama H, Ohgaki S. Photoreactivation of Escherichia coli after low- or medium-pressure UV disinfection determined by an endonuclease sensitive site assay. Appl Environ Microbiol. 2002;68(12):6029-6035.

Disinfection vs sterilization

The PureFize technology is designed for disinfection. It is important to understand the difference between disinfection and sterilization as these terms are often used incorrectly.

Disinfection and sterilization are both decontamination processes. Sterilization is a process that destroys or eliminates all forms of microbial life and is carried out in medical and health-care facilities. It is usually done through combinations of heat, irradiation, filtration, high pressure, etc. A product that has been sterilized is safe for use in an operating procedure or as an implant.

Disinfection describes a process that eliminates almost all harmful microorganisms. The level of disinfection is described using a standard called logarithmic (log) reduction. When evaluating products for high-level disinfection, their log reduction capability is paramount. The table below shows log reduction levels with the corresponding germ reduction for the case where the starting point is 1,000,000 microorganisms.

 

Log reduction

Number of microorganisms remaining

Percentage reduction

Log 0

1,000,000

0%

Log 1

100,000

90%

Log 2

10,000

99%

Log 4

100

99.99%

Log 6

1

99.9999%

Log 8

<1

99.999999%

 

PureFize has been shown to provide extremely high germicidal reduction in a short time. Up to log 8 microbial inactivation has been proven, which puts the PureFize technology as close to sterilization as it is possible.

Types of germicidal lamps

Several technologies can be used to produce UV light.

Mercury based UV lamps are so far the most common type of germicidal lamps and have been used since the 1930s. They are filled with mercury, which is in gas form during operation. There are two major types differentiated by the mercury vapor pressure in the lamp. Low-pressure lamps emit at a wavelength of 253.7nm. High pressure lamps radiate many different wavelengths, rather than a single bandwidth.

UVC LEDs are a relatively new technology. They use semiconductor materials to produce light and can be manufactured to target very specific and narrow wavelengths. This allows solutions to be tailored to the particular application need. As applications for UVC LEDs expand, the number of providers increases, which offers more choices, but also variation in provider product specifications.

PureFize is 100% mercury-free and builds on the principle of field emission in a nanostructured environment. Field emission is discharge of electrons from the surface of a material due to the presence of a strong electric field. The electrons strike the inside of a lamp glass coated with light powder (luminescent layer) and a very thin conductive layer, creative light. The properties of the light, such as wavelength, are controlled by the light powder.

Mercury and the environment

Mercury (Hg), also known as quicksilver, is a naturally occurring element found in rocks in the earth’s crust. It is released to the atmosphere from natural sources and through anthropogenic processes. Once released, it persists in the environment and becomes concentrated as it rises up the food chain, reaching its highest level in large predator fish. High exposure to mercury is a serious risk to human health and to the environment.

In 2013, the United Nations Environmental Programme (UNEP) initiated the Minimata Convention on Mercury. The convention entered into force in 2017 and has been ratified by more than 100 countries. Although it does not specifically prohibit the manufacture and sales of UV mercury lamps, it encourages a more widespread adoption of other technologies.

UV light and ozone

The shortest UV wavelengths are referred to as VUV or Vacuum UV light. Some UVC devices produce light in these wavelengths. Unfortunately VUV also generates ozone, which is effective as germicide but has a variety of adverse health effects.

PureFize does not involve VUV and thus provides highly effective disinfection without producing any harmful ozone.

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