As schools and colleges gear up to reopen, ultraviolet (UV) lights have come up as the best way to sanitise classrooms, pathways and seats from COVID-19.

Several studies support the efficacy of UV lights in disinfecting some living and working spaces, daily use items and even food products.

Can UV light prevent COVID-19 transmission by reducing contamination? Is it safe to use a UV light for disinfection purposes at home?

FIT breaks down these questions for you.

Yes, UV light can be used to destroy or deactivate the novel coronavirus.

UV light is produced by the sun and by special lamps and are divided into three main types - UVA, UVB, and UVC - based on their wavelengths.

Research shows that the UVC light that has the wavelengths of light from 200 to 280 nanometers is able to inactivate the genetic material in previously seen coronaviruses. A more recent study shows that it can also destroy SARS-CoV-2 virus or COVID-19.

This UVC light is much “stronger” than normal sunlight and has a wavelength that ranges from 200 to 280 nanometers.

Exposure to a wavelength of around 252-254 nanometers for 10 minutes deactivates or kills bacteria and viruses by damaging their cell walls in case of SARS-CoV-1. It can also be used for SARS-CoV-2. However, these wavelengths are extremely harmful to humans.

Studies have also shown that far-UVC light (207–222nm) efficiently deactivates human coronaviruses including SARS-CoV-2, which have not shown any harmful effects on human skin.

It depends on how one uses the UVC light for disinfection. The wavelength, dose and duration of exposure needs to calibrated carefully.

• UVC lamps may pose health and safety risks if not used properly.

• While using UV chambers for disinfection, one should make sure it’s leak-proof.

• In the case of handheld UVC device, people should make sure it is not pointed at the user.

No, direct exposure to UVC light poses harmful effects like skin burns and eye injury in humans and pets.

The World Health Organisation (WHO) has also said that UVC lamps should not be used to disinfect hands or other areas of one’s skin.

According to the United States Food and Drug Administration, (FDA),

• Direct exposure to UVC radiation can cause skin burns and painful eye injury.
• Some UVC lamps produce ozone and it can cause irritation when breathing.
• Extended exposure to UVC lights can degrade certain materials, such as plastic, polymers, and dyed textile.

WHO also recommends the use of chemical disinfectants for sanitising surfaces and products. However, chemical disinfectants have residual effects and cannot be used to disinfect many articles like eatables, laptops, phones, watches etc.

UVC light does not have a residual effect and can successfully sanitise these products.

Can exposure to sunlight protect you from COVID-19?

Sunlight is a source of UV light but it’s mostly UVA and UVB light. These types of UV lights are not as effective at deactivating SARS-CoV-2 as UVC light.

Moreover, prolonged exposure to sunlight can also lead to skin damage, sunburn, or even skin cancer.