National Institute for Occupational Health weighs in on UCT student model using UVC to kill Covid-19

A student looking through a microscope in the lab (PHOTO: Sanjeri/Getty Images)
A student looking through a microscope in the lab (PHOTO: Sanjeri/Getty Images)
Sanjeri

A University of Cape Town (UCT) engineering professor challenged his students to come up with innovative ways to curb the spread of Covid-19 and aid in the nation’s response to the virus. An invention by an electrical engineering student sheds light on the use of ultraviolet-C (UVC) light as a multipurpose disinfectant.

Rowyn Naidoo’s cost-effective smart UVC light system design is said to simply the sanitisation of large and small rooms, like lecture halls and classrooms, and face masks which could be disinfected and reused – ending the war on personal protective gear being in short supply.

His design hinges on the use of UVC light, also referred to as ultraviolet germicidal irradiation (UVGI), as it has a strong germicidal effect and is widely used in the form of mercury lamps to deactivate microorganisms in water and on surfaces and those that are airborne.

Dr Tanusha Singh from the National Institute for Occupational Health (NIOH), a division of the National Health laboratory service, says they have been actively involved in the use of UVC as a disinfectant for several years and explains that UVC protons emitted become absorbed by proteins, RNA and DNA of microorganisms, “which ultimately leads to the disruption of the cell membranes and its ability to replicate”, she says.

“UVC destroys viruses by high energy electrons passing through or diffusing through the protein coat into the nucleic acid core, resulting in damage of the viral RNA (coronaviruses). A cell that cannot replicate cannot cause disease,” Singh adds.

Rowyn’s design uses a cost-effective approach of implementing UVC in a model that uses layers of aluminium foil and reuses materials for the outer structure. Speaking to UCT campus media, he said his cheaper design will still get the job done. “While there are some commercially available UVC disinfection products, this project will provide automatic, optimised disinfection on a much larger scale, such as entire rooms.”

His design will use additional apparatus with the light to ensure that the light is on when there is no one inside the room. Because UVC rays can be harmful to human skin, his design will feature trip sensors and motion detectors to sense for human presence in the room and switch the lights off.

Singh explains that different microorganisms require a different magnitude of UVC targeting and that is still not known for the novel Sars-CoV-2 which causes Covid-19.

“The UVC rays or irradiance produced by a device must be able to make contact with the microorganism (fungi, bacteria eg TB or virus eg influenza) to penetrate the membrane and disrupt the DNA or RNA. If the surface contains grit, it makes it difficult for the UV rays to penetrate the soiled layers to target the microorganism. And, may not reach shadowed surfaces or nooks and crannies.”

For these reasons, Singh suggests it is still best to use UVC along with other precautionary measures. “UVC is a supplementary control and should be used to complement existing controls. For example, when other controls like ventilation is not sufficient to reduce risk. UVC is commonly used in healthcare settings, laboratories and pharmaceuticals to disinfect the air and accessible surfaces.”