Can You Disinfect Your Mask With Sunlight? Not Exactly

07-20-20

With the covid-19 running rampant around the world, masks have been mandated. This brings up many questions of how should you clean your masks and how often? Is sunlight really a good way to clean them?

I’ve seen lots of masks, especially disposables hanging from car’s windshield mirrors. When I ask the people why they do that, the statements are the same… “the sunlight will disinfect it. It’ll save me time from cleaning and I don’t need to throw it away.”

There are many reports on social media that have claimed that sunlight can disinfect. Should you believe it?

In short: no. Here’s why.

And for the covid-19… There’s only one type of UV that can reliably inactivate Covid-19 – and it’s extremely dangerous.

Dangerous Exposure
Sunlight contains three types of UV. The first type is UVA. This makes up the majority of the ultraviolet radiation reaching the Earth’s surface. It’s what deeply penetrates into the skin and is thought to be responsible for up to 80% of skin ageing, from wrinkles to age spots.

Secondly there’s UVB, which is commonly known to damage the DNA in our skin, leading to sunburn and eventually skin cancer. Both UVA & UVB are reasonably well known, and can be blocked out by most good sun-screen.

The third type is UVC. This has a shorter energetic wavelength of light. It’s filtered out by ozone in the atmosphere long before it reaches our fragile skin. Most of us are unlikely to have ever encountered any. That’s a good thing as it is particularly good at destroying genetic material – whether in humans or viral particles.

UVC
Since 1787 scientists discovered that they could harness UVC artificially to kill microorganisms. This has become a staple method of sterilization – one used in hospitals, airplanes, and high risk areas. It has also been used in the process of sanitizing drinking water; some parasites are resistant to chemical disinfectants such as chlorine, so it provides a fail-safe.

In a recent study – which looked at whether UVC could be used to disinfect PPE – it was noted while it is possible to kill the virus this way, in one experiment it needed the highest exposure out of hundreds of viruses that have been looked at so far. The amount of ultraviolet required varied widely, depending on factors such as the shape and type of material the virus was on.

UVC is really not safe to anyone to be exposed to– you shouldn’t be exposed to it. What normally can take hours to get sunburn from UVA/UVB, only takes seconds from UVC. If your eyes are exposed, they can become damaged just after a few seconds.

So is Sunshine a Potential Solution?
Would UVA or UVB work instead by leaving them out in the sun?

The short answer: Maybe – but I wouldn’t want to rely on it.

The WHO is discovering that sunlight has a potential means of sterilizing with water. The technique involves pouring the water into a clear glass or plastic bottle, and leaving it out in the sun for six hours. They believe that it might work because the UVA in sunlight reacts with dissolved oxygen to produce unstable molecules such as hydrogen peroxide, the active ingredient in many household disinfectants, which can damage pathogens.

Without water, sunlight may help with disinfecting surfaces – but it may take longer than you’d think and they don’t know how long it can take. As of right now, no one knows how long it takes to deactivate Covid-19 with sunlight, or what strength is needed.

Even if they did figure this out, the amount of UV in sunlight varies depending on the time of day, the weather, the season, and where in the world you live – especially which latitude – so this wouldn’t be a reliable way to kill the virus.

All this means that using sunlight to disinfect surfaces is extremely problematic.

So, please wash your mask with soap and water. Or if you use a disposable, please throw it away.