A heated debate has arisen about wearing masks in public to help protect against the Coronavirus. Our health authorities have been advising against general mask use but have not been very effective at explaining why general mask use is not recommended. I am writing this blog post to help explain, using my experience with protecting from exposure to asbestos.

I write as a chemist whose practice involves occupational health and safety (including asbestos and mold abatement, testing and monitoring). Masks and respirators have been part of my work life for decades. I have been fit-tested multiple times and for a decade was the guy sent out to fit-test workers; to run seminars on how to properly wear and maintain masks; and to train others to conduct fit-testing. I did all this in the context of mold and asbestos investigations, remediation and monitoring. This experience directly correlates to the Coronavirus pandemic.

To explain, asbestos, like Coronavirus, is a hidden killer. The asbestos fibers that kill you are invisible. Asbestos fibers are airborne and can get all over your body, but only cause damage if inhaled. Protection against asbestos provides a model for protection against Coronavirus.

As we all now know, Coronavirus is not a typical airborne disease. Primary transmission is understood to be via droplets (also called droplet spread). The current understanding is that a cough can generate thousands of droplets which typically travel no more than 3-6 feet before gravity pulls them down onto nearby surfaces. This is why “social distancing” is an important preventative mechanism.

A potential secondary mechanism of Coronavirus infection is from contact with contaminated surfaces or objects where the droplets spread. This would involve touching a surface that has infected droplets on it then touching your mouth, nose, or possibly eyes. Our current understanding, is that the virus needs to be inhaled to infect an individual so the eye thing is still hypothetical (no controlled testing has been done at this time).

Why Masks are Recommended

Let’s start with some simple facts. Masks, even home-made masks, will stop droplet spread. This is a good thing if you are an asymptomatic carrier of the virus. This is the biggest reason to wear a mask. A mask eliminates the direct air-to-air (inhalation of droplets) mechanism of infection. But a mask poses a risk of creating new mechanisms of infection (more on this later).

To stop droplet spread you don’t need a medical mask. Even a make-shift mask will catch the vast majority of infected droplets. Thus a mask will interrupt the direct transmission of droplets…which is a very good thing. As the health authorities have repeated, if you have Coronavirus, or believe you may have been exposed then you should avoid contact with all others and if you absolutely must venture outdoors you should be wearing a mask.

Why Masks are not recommended

Having established that masks are important for some, why aren’t they good for all? The answer has several parts but they break down to two biggies:

• Wearing a mask can cause individuals to relax their social distancing while creating a mass of potentially biohazardous materials to be disposed; and
• Wearing a mask creates whole new mechanisms of transfer (mode of infection) and leads to a host of issues with contact control.

Masks versus social distancing

The first of these is really easy to understand. If we feel that masks are going to protect us from airborne transmission then masks are more likely to reduce our attention to social distancing. We know, social distancing works and any action that reduces that action is bad. But there is a second issue.

If you are asymptomatic and are using a mask to protect the public that mask becomes a reservoir of viral material. If your mask is not replaced regularly it becomes a biohazard and if it is disposed of inappropriately it poses a risk to any individual who comes in contact with it (more on this later).

Mask provide a new mechanism of viral transfer

Now here is the part the doctors have been really bad at explaining. As I noted above, asymptomatic masks wearers don’t just shed virus via airborne droplets. They also shed viral materials when the droplets hit surfaces. But what is not considered is these masks become viral reservoirs. Cough a few times and your entire masks is now covered in virus. Then every time you touch that mask your hands get re-infected. Since masks are uncomfortable mask wearers tend to touch their face more than non-mask wearers. This mask-to-hand transfer mechanism negates a lot of the benefits of regular hand-washing. If you wash your hands then touch your infected mask you now have re-infected hands.

Then we have the unaffected mask wearer. Sure they are protected from direct transfer but should they touch an infected surface (from asymptomatic infected individuals) they run the risk of then transferring that material onto their masks (hand-to-mask).

Even if the mask protects the user from airborne droplets it does so only for a short time. Because these masks are not designed to stop the migration of virus particles through the mask (the weave is too large and the virus too small) if your mask gets exposed then it goes from being a protection to a source of aerosolized virus particles. The virus on the outside of the mask will get inhaled through the mask. So your mask is only of use if you replace it regularly.

To put this in a way more can understand. My kids love their vaporizers. They put the aroma scents into the vaporizers and then inhale the generated vapours all evening. An infected masks becomes a vaporizer for Coronavirus until it is replaced.

Not only is the affected mask a vapourizer, that mask then becomes a new secondary reservoir of infected material. This then recreates the problem we faced earlier, that impacted mask then becomes a source of viral particles that helps defeat hand-washing. When an unaffected person touches their infected mask (because the mask is annoying) and then touches another surface they have created a new mechanism of transfer (hand-to-mask-to-hand).

But we aren’t done yet. One of the saddest parts of the asbestos story was the effect of asbestos on the children of asbestos workers. Not only were the workers affected, but since the fibres got on their clothing, which they wore home, they brought the asbestos problem home with them. This was discovered when children of asbestos workers got lung cancer from exposure to their parent’s laundry.

This begs the question, what happens when those home-made masks come home. If you are using a bandanna as a mask your aren’t going to throw it away. Instead it will likely go into the laundry hamper, and the cycle continues. This creates a completely new mechanism of transfer (mask-to-family member).

Conclusion

To be clear, a lot of these mechanisms of transfer can be addressed. But each involves changing the way we behave. Learning not to touch our faces so the infected mask doesn’t re-infect our freshly washed hands is one thing we can learn. Another is ensuring that clothing worn outside goes directly into the washer (not the hamper) which would eliminate another mechanism of transfer. But ultimately the problem exists that there are not enough masks to go around and any mask that is re-used becomes a potential petri dish serving as a reservoir to re-infect users and their family members.

From my perspective it is easy to see where our public health officials are coming from. An individual practicing good social distancing ,while not wearing a mask, runs a very low risk of direct inhalation but in doing avoids three other mechanisms of transfer (mouth-to-hand; hand-to-mask-to-hand; and mask-to-family member). Moreover, since a make-shift mask provides little protection and an infected mask runs risk of the vapourizer effect while potentially reducing our desire to social distance it is easy to see why some health officials don’t recommend wearing masks.

photo credit from CTV news.