How Ultraviolet Light Can Disinfect Indoor Spaces

How Ultraviolet Light Can Disinfect Indoor Spaces
Institutions like hospitals and transit systems have been using UV disinfection for years.
Sergei Bobylev\TASS via Getty Images

Ultraviolet light has a long history as a disinfectant and the SARS-CoV-2 virus, which causes COVID-19, is readily rendered harmless by UV light. The question is how best to harness UV light to fight the spread of the virus and protect human health as people work, study, and shop indoors.

The virus spreads in several ways. The main route of transmission is through person-to-person contact via aerosols and droplets emitted when an infected person breathes, talks, sings or coughs. The virus can also be transmitted when people touch their faces shortly after touching surfaces that have been contaminated by infected individuals. This is of particular concern in health-care settings, retail spaces where people frequently touch counters and merchandise, and in buses, trains and planes.

As an environmental engineer who studies UV light, I’ve observed that UV can be used to reduce the risk of transmission through both routes. UV lights can be components of mobile machines, whether robotic or human-controlled, that disinfect surfaces. They can also be incorporated in heating, ventilating, and air-conditioning systems or otherwise positioned within airflows to disinfect indoor air. However, UV portals that are meant to disinfect people as they enter indoor spaces are likely ineffective and potentially hazardous.

What is ultraviolet light?

Electromagnetic radiation, which includes radio waves, visible light and X-rays, is measured in nanometers, or millionths of a millimeter. UV irradiation consists of wavelengths between 100 and 400 nanometers, which lies just beyond the violet portion of the visible light spectrum and are invisible to the human eye. UV is divided into the UV-A, UV-B and UV-C regions, which are 315-400 nanometers, 280-315 nanometers and 200-280 nanometers, respectively.


 Get The Latest By Email

Weekly Magazine Daily Inspiration

The ozone layer in the atmosphere filters out UV wavelengths below 300 nanometers, which blocks UV-C from the sun before it reaches Earth’s surface. I think of UV-A as the suntanning range and UV-B as the sun-burning range. High enough doses of UV-B can cause skin lesions and skin cancer.

UV-C contains the most effective wavelengths for killing pathogens. UV-C is also hazardous to the eyes and skin. Artificial UV light sources designed for disinfection emit light within the UV-C range or a broad spectrum that includes UV-C.

How UV kills pathogens

UV photons between 200 and 300 nanometers are absorbed fairly efficiently by the nucleic acids that make up DNA and RNA, and photons below 240 nanometers are also well absorbed by proteins. These essential biomolecules are damaged by the absorbed energy, rendering the genetic material inside a virus particle or microorganism unable to replicate or cause an infection, inactivating the pathogen.

It typically takes a very low dose of UV light in this germicidal range to inactivate a pathogen. The UV dose is determined by the intensity of the light source and duration of exposure. For a given required dose, higher intensity sources require shorter exposure times, while lower intensity sources require longer exposure times.

Putting UV to work

UV disinfection, which can be performed by robots like this, reduces hospital-acquired infections (how ultraviolet light can disinfect indoor spaces)UV disinfection, which can be performed by robots like this, reduces hospital-acquired infections. Marcy Sanchez/William Beaumont Army Medical Center Public Affairs Office

There is an established market for UV disinfection devices. Hospitals have been using robots that emit UV-C light for years to disinfect patient rooms, operating rooms and other areas where bacterial infection can spread. These robots, which include Tru-D and Xenex, enter empty rooms between patients and roam around remotely emitting high-power UV irradiation to disinfect surfaces. UV light is also used to disinfect medical instruments in special UV exposure boxes.

UV is being used or tested for disinfecting busses, trains and planes. After use, UV robots or human-controlled machines designed to fit in vehicles or planes move through and disinfection surfaces that the light can reach. Businesses are also considering the technology for disinfecting warehouses and retail spaces.

The New York City Metropolitan Transit Authority (MTA) is testing the use of ultraviolet light to disinfect out-of-service subway cars.The New York City Metropolitan Transit Authority (MTA) is testing the use of ultraviolet light to disinfect out-of-service subway cars. MTA, CC BY-SA

It’s also possible to use UV to disinfect air. Indoor spaces like schools, restaurants and shops that have some air flow can install UV-C lamps overhead and aimed at the ceiling to disinfect the air as it circulates. Similarly, HVAC systems can contain UV light sources to disinfect air as it travels through duct work. Airlines could also use UV technology for disinfecting air in planes, or use UV lights in bathrooms between uses.

Far UV-C – safe for humans?

Imagine if everyone could walk around continuously surrounded by UV-C light. It would kill any aerosolized virus that entered the UV zone around you or that exited your nose or mouth if you were infected and shedding the virus. The light would also disinfect your skin before your hand touched your face. This scenario might be possible technologically some day soon, but the health risks are a significant concern.

As UV wavelength decreases, the ability of the photons to penetrate into the skin decreases. These shorter-wavelength photons get absorbed in the top skin layer, which minimizes DNA damage to the actively dividing skin cells below. At wavelengths below 225 nanometers – the Far UV-C region – UV appears to be safe for skin exposure at doses below the exposure levels defined by the International Committee on non-Ionizing Radiation Protection.

Research is confirming these numbers using mouse models. However, less is known about exposure to eyes and injured skin at these Far UV-C wavelengths and people should avoid direct exposure above safe limits.

Research suggests that far UV-C light might be able to kill pathogens without harming human health:


The promise of Far UV-C for safely disinfecting pathogens opens up many possibilities for UV applications. It’s also led to some premature and potentially risky uses.

Some businesses are installing UV portals that irradiate people as they walk through. While this device may not cause much harm or skin damage in the few seconds walking through the portal, the low dose delivered and potential to disinfect clothing would also likely not be effective for stemming any virus transmission.

Most importantly, eye safety and long-term exposure have not been well studied, and these types of devices need to be regulated and validated for effectiveness before being used in public settings. The impact of continuous germicidal irradiation exposure on the overall environmental microbiome also needs to be understood.

As more studies on Far UV-C bear out that exposure to human skin is not dangerous and if studies on eye exposure show no harm, it is possible that validated Far UV-C light systems installed in public places such as retail shops and transportation hubs could support attempts at controlling virus transmission for SARS-CoV-2 and other potential airborne viral pathogens today and into the future.The Conversation

About the Author

Karl Linden, Professor of Environmental Engineering and the Mortenson Professor in Sustainable Development, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

books_science

Monday, 24 July 2023 16:37

Uterine fibroids, or leiomyomas, are benign tumors commonly occurring in the uterus. They affect many women, particularly African Americans, and can lead to clinical symptoms such as abnormal...

Friday, 21 July 2023 15:37

During uncomfortably hot weather, people seek ways to cool down their homes. Air conditioners often become the default solution when temperatures rise as they provide fast and effective relief from...

Friday, 21 July 2023 14:28

  Brushing your teeth is essential for maintaining optimal oral health, but like most aspects of health, the full story is more complicated.

Friday, 21 July 2023 06:06

Are you seeking a gentle yet powerful practice that brings balance to your body and mind? Look no further than Tai Chi. 

Friday, 21 July 2023 05:40

  As the world grapples with the ongoing COVID-19 pandemic, there has been a surge of interest and concern regarding vaccines. Vaccines play a crucial role in preventing infectious diseases,...

Thursday, 20 July 2023 22:38

As the temperatures rise during the summer months, it's important to be aware of the risks associated with extreme heat.

Thursday, 20 July 2023 15:45

People who exercise only on the weekend have similar heart-health benefits as those who exercise throughout the week

Wednesday, 19 July 2023 17:42

The World Health Organisation (WHO) recently reported that around one in six couples globally are affected by infertility. For many years people tended to blame women for a couple’s infertility –...

AVAILABLE LANGUAGES

English Afrikaans Arabic Chinese (Simplified) Chinese (Traditional) Danish Dutch Filipino Finnish French German Greek Hebrew Hindi Hungarian Indonesian Italian Japanese Korean Malay Norwegian Persian Polish Portuguese Romanian Russian Spanish Swahili Swedish Thai Turkish Ukrainian Urdu Vietnamese

follow InnerSelf on

facebook icontwitter iconyoutube iconinstagram iconpintrest iconrss icon

 Get The Latest By Email

Weekly Magazine Daily Inspiration

Friday, 02 April 2021 08:02

  Microdosing has become something of a wellness trend in recent years. The practice involves taking a low dose of a psychedelic drug to enhance performance, or reduce stress and anxiety.

Tuesday, 20 April 2021 08:05

Wild bees are essential for sustaining the landscapes we love. A healthy community of wild pollinators ensures that most flowering plants have an A-team pollinator species and a reserve bench of...

Tuesday, 18 May 2021 16:15

In my blog posts, free resources, and courses, I talk a lot about the things that we can do to support and develop our inborn, natural interspecies communication abilities. In this post, I...

Sunday, 02 May 2021 08:18

When you think about soil, you probably think of rolling fields of countryside. But what about urban soil? With city dwellers expected to account for 68% of the world’s population by 2050, this oft...

Sunday, 16 May 2021 14:24

The human body is an amazing thing, full of systems, organs, nerves, and vessels that work together in harmony. You’ve seen the body described as a machine, as a city, or even as a factory....

Wednesday, 21 April 2021 07:23

Whether it’s your arthritic relative who knows rain is on the way when their knees ache or your lifelong pal who gets a headache when a storm is approaching, we all know somebody who claims they...

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.