Ultraviolet Sterilisation

UV radiation has been shown to inactivate the virus that causes COVID-19, though further research is needed to exactly determine safe exposure doses. Different UV wavelengths cause photochemical reactions that target different cellular processes and inactivate microbes at varying rates.


Industrial-grade UV germicidal irradiation systems are highly effective at controlling airborne pathogens like fungi, bacteria and viruses. However, sanitizers sold for home use may be less powerful.

Inactivation of Microorganisms

Due to an increase in hospital-associated infections and multidrug-resistant bacteria, new cleaning and disinfection techniques are being sought, especially for near patient environments. UV irradiation is a chemical-free method that has been shown to be effective in the inactivation of microorganisms. This method of sterilization can be used in food processing and water treatment systems to prevent contamination with pathogenic organisms and reduce the risk of outbreaks and infections.

UV-C radiation causes DNA and protein damage in microorganisms, which inhibits their ability to reproduce. This makes it an effective disinfectant, even for drug resistant bacteria. It is also very easy to use and does not leave any chemical residue.

However, the antimicrobial effect of UV-C irradiation can be significantly affected by environmental factors. For example, the absorption and shadowing effects of surrounding organic and inorganic substances can greatly diminish UV-C radiation’s effectiveness.

In addition, the wavelength of UV-C light influences its efficacy. For example, the far-UVC radiation (220 nm) is more effective than the deep-UVC radiation (260 nm).

This is because it penetrates deeper into cells, causing a more extensive DNA and protein damage. Moreover, the antimicrobial effect of UV-A is less dependent on these factors because it acts by activating naturally occurring constituents in water or target cells. These reactive species then cause hydroxyl radicals that damage the cell’s membranes and proteins, which inactivates the microorganisms.

Sterilization of Food

As a sterilization technique, UV radiation can be used to treat all major liquid and solid food groups. This approach is an alternative to chemical treatment methods and can be used in combination with existing processing techniques (e.g. thermal and pasteurization).

It is also a cost-effective method for disinfection, as it does not require any additional equipment or chemicals. Additionally, UV irradiation is less energy-intensive than other types of light, making it an environmentally friendly option.

In the case of fresh fruit and vegetables, UV-C has been shown to reduce or eliminate a number of pathogens, including E. coli, salmonella and listeria. This is due to the fact that these bacteria have very thin cell walls, which makes them very susceptible to UV rays. In contrast, mold spores have much thicker cell walls and are often pigmented, which means they are more resistant to UV rays.

As a result of these findings, several juice-manufacturing companies have integrated UV-C irradiation into their production lines. This has become a critical part of their Hazard Analysis and Critical Control Points, especially as the FDA recently mandated that most juice-manufacturing facilities use this method to avoid future E. coli outbreaks. Furthermore, UV-C treatment can eliminate the need for chemical sterilizers in frozen foods. This translates into lower production costs and better overall product quality for the end consumer.

Sterilization of Water

UV light disinfects water by destroying germs. This technique is especially effective against bacteria but also kills viruses and protozoans like Giardia lamblia cysts or Cryptosporidium oocysts. The radiation is very energetic and can break chemical bonds. The energy is much higher than that of visible light but lower than that of x-rays.

UV rays attack the DNA of microorganisms. This breaks down the structure and makes it impossible for organisms to reproduce. The damage causes mutations which render them unable to cause infections. This is known as a bacteriostatic effect, not a bactericidal one.

The effectiveness of UV treatment depends on the length of exposure to the light and the intensity of the lamp. The US Department of Health recommends a minimum exposure time of 90 seconds for 1 L of water (default setting on the SteriPEN).

In addition, the SteriPEN uses a specialized spectral filter that eliminates all UV-B and -C and a significant fraction of UV-A rays. It has been demonstrated that PET and glass bottles filter out the entire UV-A spectrum and only a small fraction of UV-B and –C passes through the bottle material.

Sterilization of Environment

In contrast to chemical or heat disinfectants, UV rays inactivate microorganisms by targeting their genetic material and speeding up the cross-linking of its molecules. This prevents cellular reproduction and limits the organism’s ability to carry out vital functions, including respiration and growth.

This form of sterilization is commonly known as germicidal irradiation. It can be used to disinfect air, surfaces, and liquids. However, effective inactivation of microorganisms depends on the degree of exposure to UV light. This is influenced by the size of the target organism, its shape and surface characteristics, the wavelength of the UV radiation being used, and the concentration of the target substance. It is also influenced by the presence of shadowing effects. For example, forced-air systems by design impede line-of-sight of the UV radiation and can create areas where the inactivation rate is significantly reduced.

When choosing a device that uses UV rays to sterilize the environment, make sure it is specified as using germicidal UV radiation. This will ensure it is within the wavelength range (100-280 nm) that is able to penetrate the cellular structure of microorganisms and inactivate them. It is important to follow all manufacturers’ instructions on the use of these devices, especially regarding light-source distance, exposure time and safety precautions. With the increase in hospital-acquired infections, multidrug- and extensive drug-resistant bacteria and viruses such as the severe acute respiratory syndrome coronavirus (SARS-CoV) pandemic since December 2019, it is even more important to pay close attention to hygiene and sanitation in order to avoid infection.