UV radiation and blue light disinfection – what are their differences?

LED Tailor Oy is a leading specialist in light-based disinfection technologies. We manufacture disinfection products using both LED-UVC and visible blue light. In this article we compare UVC and blue light technologies and situations in which they excel.

Ultraviolet (UV) radiation is well-known for its antimicrobial properties. It is a well-established solution for disinfection of surfaces, air and water, and has been in use for decades. The UV part of the electromagnetic spectrum of light comprises wavelengths in the 100 to 400 nanometer range. The most efficient wavelengths used for disinfection purposes are within the UVC band, at around 254-265 nanometers. The term UVC disinfection typically refers to UVC radiation at this narrow range.

Antimicrobial blue light (aBL) means certain wavelengths of visible light inside the blue band, within 405-470 nanometer range. While the antimicrobic properties of visible blue light have been known for decades, blue light disinfection has only become practical and economically viable relatively recently through innovation and rapid advancements in LED technology. LED Tailor's Spectral Blue technology is based on multi-wavelength visible blue light.

Figure: Electromagnetic spectrum of light and different wavelength bands.
Spectral Blue devices operate on specific antimicrobial
wavelengths between 405 and 470 nanometers.

Video: How multi-wavelength blue light works

Both UVC radiation and visible blue light are effective antimicrobial tools. However, their mechanisms of action are based on very different principles. In UVC radiation, the photons are absorbed by DNA and RNA molecules in a way that causes damage to living cells. Illumination with antimicrobial blue light, on the other hand, causes the forming of reactive oxygen species (ROS) inside microbial cells. The ROS are highly reactive oxygen molecules that can damage the vital structures of microbial cells.

Due to its superior safety, lower lifecycle costs, and lower overall environmental impact, blue light disinfection provides better value than legacy systems based on UVC disinfection such as UVC tubes.

Impacts on Health

Blue light does not damage living cells directly. Its mechanism of action is based on activating light-absorbing compounds, which are present in all microbial cells but not in human cells. This means that human cells do not react to blue light and it is completely safe for humans. Neither does blue light produce ozone. 

While Spectral Blue devices are designed to be used when no people are present, this is only because very bright blue light can be straining on the eyes. Spectral Blue devices have been tested and proven to be safe for eyes in normal use according to Blue Light Hazard standard. Looking directly at any bright light sources is however not recommended. As a summary, there are no known negative health impacts and no safety protocols are needed for users of blue light disinfection.

The efficiency of UVC disinfection is based on the ability of UVC radiation to damage DNA and RNA strands. While there are different types of UVC radiation sources, generally they all constitute a health hazard for users. Specific hazards may depend on the kind of lamp and how it is installed. Since UVC radiation damages also human DNA, it is a well-known carcinogen and may also cause burn-like skin damage. Invisible UVC radiation also causes eye damage.

Some UVC lamps produce ozone, which is harmful when inhaled. The most common type of UVC radiation sources, UVC tubes, also contain mercury, which is highly toxic even in small quantities. It is not irrelevant how UVC disinfection devices are installed, used and disposed of. Their use requires staff training and safety measures.

Unlike UVC tubes, UVC LEDs do not produce ozone and do not contain mercury. That is why LED Tailor uses only UVC-LED technology in its UVC-based DS disinfection cabinet.

Degradation of Materials

Visible blue light has less energy than UVC radiation and does not have the ability to break down polymers and degrade materials such as plastics. Blue light does not damage the room’s surface materials or equipment.

High-energy UVC radiation (and UV radiation in general), on the other hand, is known to degrade many materials. These include most plastics, other polymers and pigments found in paints and dyed textiles. UVC is known to cause color transformation, yellow hue, and signs of aging in many materials. Degraded materials may also become brittle.

UVC solutions can therefore cause extra expenses and effort to repair material damage or replace the degraded materials. The lifespan of expensive laboratory or healthcare equipment is also shortened by UVC damage.

Recent research also shows that material degradation caused by UVC radiation generates particle emissions into the room air.

Ability to Penetrate Materials - and Biofilm

Blue light is very effective at penetrating a multitude of materials, including clear plastics, clear glass and water. Blue light also penetrates biofilms more efficiently than UVC, making it more efficient in eliminating microbes that grow under the protective shelter of biofilm. The forming of biofilms is a common defense mechanism for many microbes. They constitutes a significant risk factor in many industries and clean manufacturing facilities.

UVC radiation does not penetrate materials like glass and most plastics. Depending on material, it may also reflect less well from surfaces compared to visible light. This means UVC disinfection solutions can be less practical to implement and can leave blind spots and shadows.

UVC radiation has also limited capacity to penetrate biofilm.

Antimicrobial Resistance in Microorganisms

Blue light does not promote the development of antimicrobial resistance. This is as the reactive oxygen species cause so wide-ranging and non-specific damages inside the microbial cells that it would be very difficult for the microbes to learn to repair and adapt to it all at once.

Since UVC has only one mechanism of action (damages DNA and RNA strands), it is possible that some microbes can learn to repair the damages and develop resistance towards UVC radiation under repeated contact. Such adaptation can occur if the radiation dosage is not sufficient to kill the colonies.

Lifespan and Costs

LED-based blue light devices contain no toxic chemicals and are easy to recycle. Because they require no tube changes and do not generate hazardous waste, they have a lower lifecycle cost than many UVC solutions.

Most commercially available UVC disinfection systems still employ UVC tubes, which have a relatively short expected lifespan, only approximately 8 000 hours. Their output significantly decreases during that time. Typically it is recommended that UVC tubes are replaced every year, which causes additional costs during the lifecycle of the UVC appliance. UVC LEDs have similar lifespan, but their output does not degrade as rapidly and can be cycled on/off repeatedly without issues.

Blue light disinfection systems use modern LED components, which have a significantly longer lifespan, up to 50 000 hours, and do not decrease in output significantly.

Furthermore, UVC tubes contain mercury, which is a hazardous material. Mercury is not only a health hazard for the user; it is also a liability due to the difficulty and costs of recycling the appliances that are at the end of their lifecycle.

Overall Value

Overall, as the only disinfection method without any negative side effects, blue light provides a unique solution due to its unrivalled safety, lower environmental impact, lower life cycle costs, and ease of use. It’s the obvious choice of leading professional organizations. Thanks to its many advantages, blue light is the best choice when you need to disinfect whole rooms.

Use of UVC radiation in disinfection solutions comprises a broad range of different appliances and tools, but its high lifecycle costs, health risks and adverse environmental effects make it less well suited for the increasing sustainability requirements of today’s world. In general, we see that UVC is best used in closed systems like disinfection cabinets and inside air ventilation ducts.

There have been promising recent developments in “Far-UVC” disinfection, which exploits the shortest wavelengths of the UVC band (222 nm). Far-UVC disinfection can have potential to make UVC disinfection safer and more viable in the future. However, most Far-UVC related innovations are still in their infancy and require significant safety research and product development to have comparable performance to UVC or blue light.

Technology / suitability table:

Performance-wise, UVC requires less energy to inactivate microbes. This means that a blue light device with similar electric power has to be on for a longer time to achieve same results as UVC. However, many times such direct comparison is not meaningful, as the optimal application areas for the technologies are different. The below table gives an overview of how UVC and blue light technologies are best used.

Related articles:

• Blue light eliminates biofilm effectively
• Substantial and persistent microbial reduction in a pharmaceutical GMP facility after deploying blue light