Why public health officials advise against masks to protect from the Coronavirus – my thoughts using lessons learned from asbestos exposure

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).


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.

This entry was posted in Chemistry and Toxicology, Uncategorized. Bookmark the permalink.

15 Responses to Why public health officials advise against masks to protect from the Coronavirus – my thoughts using lessons learned from asbestos exposure

  1. Andrew Roman says:

    Thank you. An excellent explanation.

    Liked by 2 people

  2. Andrew Kennett says:

    very good explanation — shared


  3. J P says:

    The single most obvious difference between a virus and asbestos, is that the viral load on a surface will spontaneously degrade to become non-viable; unable to infect. If asbestos had spontaneously degraded in 3 days to become inert – you would have needed a different career.

    Further; you make a case that wearing a mask will cause inhalation of aerosol viruses. I believe that it’s important to know that a mask requires time-in-use to become “biologically porous”. A surgical mask is not to be used for more than 10 minutes. A n95 mask is intended for longer duration of use.

    If a person chooses to wear a simple consumer level (or even home made) mask in a social environment, for a duration of less than 10 minutes (buying milk and eggs at the store, for example); they have reduced everybody’s risk (their own and those around them). The only assumption that has to be made, is that the person has the ability to keep that contaminated mask safely untouched for the 3 days following. Like in a plastic bag on a top shelf in the laundry room maybe.


    • Blair says:

      A mask that has a pore size of 0.3 microns doesn’t need time to be biologically porous to a virus that is 0.125 microns. Similarly common fabrics have pores that are exceed 3 microns. There are like sieves being used to stop water. They serve no particular use at the microscopic level.


  4. tomadamsenergy says:

    I am a longtime admirer of your energy analysis, but I think this medical analysis suffers from two fatal flaws. First, your analysis does not account for important differences between the hazard of asbestos vs. this virus. Second, your analysis does not even acknowledge, let alone address, the very large medical literature demonstrating the effectiveness of the widespread public use of masks. (see: https://docs.google.com/document/d/1HLrm0pqBN_5bdyysOeoOBX4pt4oFDBhsC_jpblXpNtQ/edit) Public mask usage needs to be supported with education about donning/doffing, hand washing, and the continued need for quarantine but everyone in public should be using them.


    • Blair says:

      Having read about half the articles in that group I would note that all I have read deal with protection of the public from affected individuals. I noted that fact in my piece. My interest was for protection of non-affected individuals from exposure.


      • tomadamsenergy says:

        Me protecting you from this virus I might be carrying by me wearing a mask is the key point here. My mask protects you, your mask protects me. That’s why everyone should be wearing a mask when they must go out in public.


      • Blair says:

        except if you wearing your mask results in you covering every surface with virus because you keep adjusting your impacted mask….

        Liked by 1 person

      • tomadamsenergy says:

        Your point about the problem of folks touching their masks is important and must be the target of public education. A barrier to that education effort is that public health officials (WHO, CDC, Theresa “The risk to Canadians is low” Tam, etc.) have damaged their own credibility by advising against what appears to be an effective anti-viral weapon.


  5. DMacKenzie says:

    People touch their faces about 20 times an hour, which masks prevent. This effect is often ignored by anti-maskers….sure, touching your mask might contaminate your fingers, but a “touch your mask, wash your hands” rule trains people to not raise their hands to their facial area much faster than without a mask.


    • Chester Draws says:

      We aren’t going to wash our hands 20 times an hour. Not happening.

      Coughing into a tissue and throwing away the tissue would have the same effect, and far more practical when out shopping.


      • DMacKenzie says:

        You miss my point, you’re not going to touch your face 20 times an hour if you are wearing a mask, or sewing thimbles on your fingers, or finger wraps of masking tape, whatever you use to break yourself of that face touching habit. And sneezing into a bandana type mask distributes far fewer droplets than sneezing into an elbow, or a too late kleenex,


  6. DMacKenzie says:

    You miss my point, you’re not going to touch your face 20 times an hour if you are wearing a mask, or sewing thimbles on your fingers, or finger wraps of masking tape, whatever you use to break yourself of that face touching habit. And sneezing into a bandana type mask distributes far fewer droplets than sneezing into an elbow, or a too late kleenex,


  7. Pingback: Understanding Health Canada’s advice about wearing masks in public – let’s try this again | A Chemist in Langley

  8. Laura Fultz says:

    Thank you for the education I got from this article. I don’t wear a mask.


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