A team of scientists is calling for more research into how sunlight inactivates SARS-CoV-2 after realizing there is a clear difference between recent theory and experimental results.
Paolo Luzatto-Fagis, a mechanical engineer at UC Santa Barbara, and colleagues found that the virus became inactive eight times faster in experiments predicting the latest theoretical model.
“The theory assumes that inactivation damages the RNA of the virus by hitting it with UVB, damaging it,” Luzto-Fagiz explained.
But discrepancies suggest that something more than that is going on, and finding out what this is can be helpful in managing the virus.
UV light, or the ultraviolet portion of the spectrum, is easily absorbed by some nucleic acid bases in DNA and RNA, making it difficult to repair.
But not all UV lights are the same. Long UV waves, called UVAs, do not have enough energy to cause problems. It is the mid-range UVB waves in sunlight that are primarily responsible for killing microbes and putting our own cells at risk of sun damage.
Short-wave UVC radiation has been shown to be effective against viruses such as SARS-CoV-2, which are still safely absorbed into human fluids.
But these types of UV do not usually come into contact with the Earth’s surface, thanks to the ozone layer.
“UVC is great for hospitals,” said Julie McCurry, co-author and reggae State University toxicologist. “But in other environments – for example, kitchens or subways – UVC will interact with parts to produce harmful ozone.”
In July 2020, an experimental study tested the effects of UV light on SARS-Cavi-2 in simulated saliva. They noted that the virus became inactive when exposed to simulated sunlight for 10-2 minutes.
“Natural sunlight can be effective as a disinfectant for contaminants,” Wood and colleagues concluded in the paper.
Luzto-Figiz and the team compared these results with the theory of how sunlight is, which was published only a month later and saw that the math did not increase.
The study found that the SARS-CoV-2 virus is three times more susceptible to UV exposure to sunlight than influenza A, while 90 percent of coronavirus particles are inactivated after half an hour of exposure to afternoon sunlight in summer.
By comparison, light infectious particles can remain intact for days in winter.
Environmental calculations by a separate team of researchers have concluded that the RNA molecules of the virus are being photomically damaged by light rays.
This is achieved more powerfully by shorter wavelengths of light like UVC and UVB. UVCs do not reach the Earth’s surface, so they rely on calculations of their environmental light exposure on the middle-wave UVB portion of the UV spectrum.
“The inactivity observed experimentally in silhouetted saliva is eight times faster than expected by theory,” Luzto-Figiz and colleagues wrote.
“Therefore, scientists do not yet know what is going on,” Luzto-Fagiz said.
Researchers suspect that instead of directly affecting RNA, long-wave UVA may interact with molecules in a test medium (simulated saliva) that accelerates the inactivation of the virus.
Something similar is found in wastewater treatment – where UVA reacts with other substances to form molecules that damage the virus.
If the UVA. While SARS-CoV-2 can be used to counteract, cheap and energy-efficient wavelength-specific light sources may be useful for enhancing air filtration systems at relatively low risk to human health.
“Our analysis points to the need for additional experiments to test the effect of specific light wavelengths and medium composition separately,” concludes Luzto-Fagis.
With the ability to keep this virus in the air for extended periods of time, safe means to avoid it in countries where it runs very fast and to wear a mask where distance is not possible. But it’s nice to know that sunlight can help us during the warmer months.
His analysis was published in Journal of Infectious Diseases.