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Visible light that’s safe and effective for combatting healthcare-associated infections

“The efficacy of manual cleaning procedures can vary considerably among hospitals.”

October 7, 2021  By Dr. Cliff Yahnke

Photo: Photographe corporatif Montréal, courtesy Kenall Manufacturing Co. Used with permission.

October 7, 2021 – The World Health Organization defines healthcare-associated infections (HAIs) as “infections occurring in a patient during the process of care in a hospital or other healthcare facility, which were not present or incubating at the time of admission”.

Approximately 20% to 40% of HAIs result from the transmission of pathogens by a healthcare worker after touching another patient or a contaminated surface.[1] HAIs include methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), C. difficile and other infections caused by bacteria and viruses.

The consequences of HAIs are significant. According to the Canadian organization Coalition for Healthcare Acquired Infection Reduction (CHAIR):

• One out of 10 Canadian patients acquires an infection from the hospital—that’s 200,000 people each year.
• 10,000 Canadians (5%) who acquire infection from a hospital will die.
• It costs Canadians $4 to $5 billion annually to treat HAIs.


The Canadian Committee on Antibiotic Resistance estimates that at least 30% of healthcare-associated infections can be prevented. Attention to cleanliness and disinfection of surfaces plays a large role in reducing HAIs. Cleaning, laundry, and other support services are a vital element of infection prevention and control strategies.

However, the efficacy of manual cleaning procedures can vary considerably among hospitals. Pathogens such as C. difficile, VRE, MRSA, norovirus, influenza, and severe acute respiratory syndrome (SARS) -associated coronavirus can survive in the healthcare environment for extended periods—even months. In fact, these infections are inherently well-adapted to survive in dust and on floors, bedrails, telephones, call buttons, curtains and other surfaces. Hand-washing is important, but if bacteria and viruses are not eliminated from the environment, hands will repeatedly become contaminated.[2] There is a clear need for technology to help mitigate HAIs.

Germicidal ultraviolet light

Evidence demonstrating the persistent contamination of environmental surfaces despite traditional cleaning and disinfection methods has led to the widespread acceptance that there is both a need for reassessing traditional cleaning protocols and for using secondary disinfection technologies.[3]

Ultraviolet (UV) disinfection is one type of no-touch technology shown to be a successful adjunct to manual cleaning in reducing environmental bioburden. This technology is designed for use in operating rooms, patient rooms, and other healthcare settings.

Essentially, UV light kills bacteria and viruses by damaging their nucleic acid, thus destroying their ability to replicate and cause disease. UV wavelengths, which are less than 400 nm, are beyond the range of visible light, and can kill pathogenic microorganisms.

Most experts agree that the C bandwidth (approx. 100 nm to 280 nm) is the most germicidal, and that UV-C light can remove approximately 99% of microbial contamination in the air and on surfaces. The energy required to kill microorganisms is a product of the UV light’s intensity and exposure time, measured in microwatt seconds per square centimetre.[4]

Short wavelengths can kill pathogens through a variety of pathways, depending on the wavelength, duration and amount of optical radiation.[5] The advantage of UV-C technologies for minimizing HAIs is that an effective dosage can be achieved with short time durations (less than one hour).[6] There are, however, disadvantages to this technology.

The disadvantage of UV-C is that the radiation must be applied when the hospital room is unoccupied, as it is inherently toxic to humans. Additionally, as a tool for disinfection, UV has other drawbacks:

• Portable devices require specialized staff and training to operate.
• Episodic: once UV disinfects the room, pathogens immediately begin to re-enter the space: in the air, on patients and staff, and on surfaces.
• UV requires line of sight to work. If a surface is in shadow, it will not be disinfected.
• UV light sources degrade. According to one manufacturer’s specs, replacement may be required in as little as four months when operated continuously.
• UV causes material degradation, damaging plastics and fading fabrics/finishes.

A visible light alternative

Scientists and engineers have developed technology that utilizes 405 nanometre Indigo visible light to provide disinfection around the clock, even when people are present. These luminaires automatically kill viruses, bacteria, molds, yeasts and fungi in the air and on surfaces without requiring specially trained staff. Unlike UV, 405-nm visible light is both direct and indirect. Reflecting off walls and other surfaces, it kills pathogens in shadowed areas UV lighting cannot reach.

Rather than relying solely on staff to clean surfaces, or HVAC systems to purify the air, this technology combines the benefits of both. Using the visible light spectrum, the technology is safe at all times—even when performing at its highest level of disinfection. No room downtime, and no worries about safety.

Case Study: 405-nm visible light in action

Knowing the seriousness of HAI issues even before Covid, the Centre Hospitalier Regional de Lanaudiere (CHRDL) in Joliette, Que., installed germicidal luminaires in the facility’s 1000-m endoscopy unit and adjacent support areas, including a medical device reprocessing unit.

The luminaires use 405-nm visible light to continuously disinfect the air and surfaces. The lights can reduce high-risk bacterial transmission events involving coagulase-negative staphylococci, and are clinically proven to reduce transmission of S. aureus—the number one cause of surgical-site infections.[7]

Although the hospital had cleaning protocols in place, staff were concerned about the human factor and the techniques used that limit the effectiveness of the application of the procedures.

Photo: Photographe corporatif Montréal, courtesy Kenall Manufacturing Co. Used with permission.

A primary driver in the selection of the technology was that the lights are controlled automatically: when the rooms are occupied, they produce a blend of White and 405-nm light. When the rooms are unoccupied, the lights switch to 405-nm Indigo-only for maximum disinfection.

GBi Experts-Conseils Inc.—a Quebec engineering firm retained by the hospital—learned about this technology at an Illuminating Engineering Society conference, and knew it would be beneficial to CHRDL.

“Despite the current protocols and procedures established for disinfection in health facilities, the human factor and the techniques used limit the effectiveness of the application of the procedures,” said Grégoire Tremblay, GBi Experts-Conseils. “The addition of an external agent that operates continuously using cutting-edge technology becomes an asset to improve the effectiveness of disinfection in more sensitive places.”

Dr. Cliff Yahnke is chief scientist and head of clinical affairs for Indigo-Clean and Kenall Manufacturing Co., a Legrand company, and can be reached at cliff.yahnke@kenall.com.


1. “Patient safety and quality: an evidence-based handbook for nurses,” Amy Collins.
2. “Healthcare associated infections: backgrounder and fact sheet,” Canadian Union of Public Employees, 26 May 2014. LINK.
3. “Ultraviolet-C: a primary means of disinfection,” Coalition for Healthcare Acquired Infection Reduction, January 2017. LINK.
4. “UV light’s germicidal properties aid in fight against HAIs,” Infection Control Today, 6 November 2008. LINK.
5.“An assessment of a hybrid lighting system that employs ultraviolet-A for mitigating healthcare associated infections in a newborn intensive care unit,” JA Brons, A. Bierman, R White, K Benner, L Deng, MS Rea, The Society of Light and Lighting, January 2020.
6. Ibid.
7. “Could visible light be a safe and effective Sars-CoV-2 disinfectant?”, Lakshmi Supriya, Ph.D., Medical Life Sciences, 17 March 2021.

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