Recognizing that there is a clear difference between the latest theory and experimental results, a group of scientists called for more research on how sunlight can inactivate SARS-CoV-2.
Paolo Luzzatto-Fegiz, a mechanical engineer at the University of California, Santa Barbara, and his colleagues noticed that the virus inactivates in experiments eight times faster than predicted by the latest theoretical model.
Luzzatto-Fegiz explained: “The theory believes that inactivation works by causing UVB to hit the virus’s RNA and cause damage to it.”
But the difference suggests that there is more to be done, and figuring out this may be helpful in managing the virus.
Ultraviolet rays or ultraviolet rays in the spectrum are easily absorbed by certain nucleic acid bases in DNA and RNA, which may cause them to bond in a way that is difficult to fix.
However, not all ultraviolet rays are the same. Longer ultraviolet waves (called UVA) do not have enough energy to cause problems. It is the medium-wave ultraviolet waves in the sun that are mainly responsible for killing microorganisms and exposing our own cells to the danger of sun damage.
Shortwave UVC radiation has been proven to be effective against SARS-CoV-2 and other viruses, even if it is still safely wrapped in the human body.
However, due to the ozone layer, this type of ultraviolet light usually does not come into contact with the earth̵
Co-author Julie McMurry, a toxicologist at Oregon State University, said: “UVC is very suitable for hospital use.” “But in other environments (such as kitchens or subways), UVC interacts with particles. Harmful ozone.”
In July 2020, an experimental study tested the effect of ultraviolet light on SARS-CoV-2 in simulated saliva. They recorded that the virus was inactivated after 10-20 minutes of exposure to simulated sunlight.
Wood and his colleagues concluded in the paper: “Natural sunlight can effectively disinfect contaminated non-porous materials.”
Luzzatto-Feigiz and their team compared these results with a theory on how sunlight achieves this goal, which was released a month later and found that the math did not add up.
This study found that the SARS-CoV-2 virus is three times more sensitive to ultraviolet rays in sunlight than influenza A. After half an hour of exposure at noon in summer, 90% of the coronavirus particles are inactivated.
In contrast, in winter light, infectious particles may remain intact for several days.
Environmental calculations performed by a separate research team concluded that the virus’s RNA molecules were directly photochemically destroyed by light.
This is achieved more efficiently with shorter wavelength light (such as UVC and UVB). Since UVC cannot reach the surface of the earth, they calculate the environmental exposure based on the mid-wave UVB part of the UV spectrum.
Luzzatto-Feigiz and colleagues wrote: “The rate of inactivation in simulated saliva observed through experiments is more than eight times faster than expected by the theory.”
Luzzatto-Fegiz said: “So scientists don’t yet know what happened.”
Researchers suspect that long-wave UVA may accelerate the inactivation of the virus, instead of directly affecting RNA, but may interact with molecules in the test medium (simulated saliva).
A similar phenomenon can be seen in wastewater treatment-UVA reacts with other substances to form molecules that destroy viruses.
If UVA can be used to combat SARS-CoV-2, then inexpensive and energy-saving wavelength-specific light sources may be useful for enhancing air filtration systems with relatively low human health risks.
Luzzatto-Fegiz concluded: “Our analysis shows that additional experiments are needed to test the effects of specific light wavelengths and medium components.”
Because this virus can stay suspended in the air for a long time, the safest way to avoid this virus in countries that are still rampant is to stay away from society and wear a mask that cannot be isolated. But it is nice to learn that the sun may help us in the warmer months.
Their analysis is published in Journal of Infectious Diseases.