Dr. Don Colbert – While the COVID-19 pandemic continues, researchers are looking for many different ways to kill the virus on surfaces and materials, and in the human body. One area of focus is UV rays and heat. Can high temperatures and UV kill COVID-19?
Here’s the current research on UV rays, the types, environmental temperatures, and high heat against COVID-19.
The Studies: Does UV Kill COVID-19?
UV light is showing promise in the fight against COVID-19.
The Solid State Lighting and Energy Electronics Center of UC Santa Barbara is studying the effects of UV light on COVID-19. In fact, this department and member companies are developing UV LEDs to decontaminate surfaces.
They believe UV LEDs can provide disinfection to personal protective equipment and medical surfaces such as floors, tables, devices, and HVAC systems in hospitals.
Another company, called Seoul Semiconductor is reporting “99.9% sterilization” of COVID-19 in just 30 seconds using their UV LED products. They specifically manufacture UV LED lamps used to sterilize the interiors of unoccupied cars.
There is promise with these applications!
How UV Kills COVID-19
However, not all UV rays are effective.
UV-A and UV-B, the length and type of UV rays we receive from the sun, do not appear to be effective against COVID-19.
UV-C, which can be utilized from specific UV LED lamps, is effective. However, even within the UV-C category, the waves must be the right length, strength, and applied for the right amount of time, depending on the surface being decontaminated.
The UV-C rays must be in 260-285 nm wavelength range. Unfortunately, they are harmful to people. Just as they kill and disrupt viruses by damaging their DNA and RNA, they can harm our cells as well when applied to our skin. Even brief exposure can cause skin burns and eye damage (1).
One study compared UV-C applied to the material of an N-95 mask and stainless steel. It took approximately 12 minutes for the virus to become completely undetectable on the stainless steel, and about 1 hour for the mask. The lamps were placed just 20 inches from the surfaces. This study demonstrates the need for accurate time, distance and wavelength for different materials (2).
Can the Sun’s Heat and UV Kill COVID-19?
It’s worth discussing the sun’s heat, and weather in general with the spread of COVID-19. With other infectious diseases, weather and temperature often play a factor in the spread.
At least one study has been published on the changing seasonal temperatures and COVID-19 spread in China. So far, neither temperature nor UV radiation from the sun has made a difference. This may be due to the time of year and temperatures logged so far during the pandemic, or it could point to the Earth’s environmental temperatures and UV-exposure as ineffective in altering the spread of COVID-19 (9).
Do Other Heat Sources Kill COVID-19?
When it comes to heat above our earthly temperatures, it is very effective against viruses and COVID-19 in a relatively short amount of time. In fact, it appears that COVID-19 is more susceptible to heat than SARS.
What kind of heat is required?
High heat, above our normal environmental temperatures, is needed to kill the virus in less than a day. But, it’s still not as high as you might think.
Interestingly, some recent tests on COVID-19 found that the virus in culture medium became undetectable after only 5 minutes at only 158°F (70°C). As temperatures were reduced, the time required to irradicate the virus increased.
At 132°F (56°C), 30 minutes is required. At 98.6°F (37°C), 2 days is required. And at 71.6°F (22°C), 2 weeks is required (9).
Again, this heat is specific for the virus in culture medium and surfaces…not for killing the virus within the human body. Once there, it can replicate faster than it’s killed until the immune system finds a way to kill it.
Still, high heat can be used to disinfect surfaces (although it can also harm specific surfaces and fabrics), and higher summer heat may help us slow it in general.
Can Room Temperature Kill COVID-19?
While room temperature does not really kill COVID-19, the virus does “die off” after a while on surfaces when left at room temperature. Researchers from Hong Kong have found when left on surfaces at room temperature and 65% relative humidity, it becomes undetectable after:
- 3 hours on regular paper and tissue
- 2 days on cloth and paper money
- at least 7 days on surgical masks, plastic, and stainless steel
What’s more, colder temperatures do help preserve it and keep it infectious (10).
There is a lot of promise with using UV-C rays to disinfect medical equipment, and potentially housewares without damaging the surfaces and materials. However, UV rays from the sun (UV-A and UV-B) do not seem to be effective to kill COVID-19. And, while studies are suggesting that high heat kills COVID-19, the temperature needs to be above 130 °F to be effective and efficient, and care must be taken to not compromise materials.
Summer temperatures may slow the virus spread as the heat around 100 °F will kill the virus quicker on surfaces as long as they are not re-infected. Still, there are many benefits to being outside including boosting your immune system and mood, so don’t give up on the sun’s UV-rays and outdoor activity (with social distancing) completely.
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