Blair King: Lessons from exposure to another airbone killer – asbestos.
A heated debate has arisen about wearing masks in public to help protect against COVID-19. 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 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 one of the guys sent to fit-test workers; run seminars on how to properly wear and maintain masks; and train others to conduct fit-testing. I did all this in the context of mold and asbestos investigations, remediation and monitoring.
This experience is directly relevant to the pandemic.
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 to 6 feet before gravity pulls them down onto nearby surfaces. This is why “social distancing” is important.
A potential secondary mechanism of Coronavirus infection is 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 – so the eye thing is still hypothetical; no controlled testing has been done that I’m aware of.)
Why masks are recommended
Let’s start with some simple facts. Masks, even homemade masks, will stop droplet spread. This is a good thing if you are an asymptomatic carrier of the virus, and the single biggest reason to wear a mask. A mask eliminates the direct air-to-air (inhalation of droplets) mechanism of infection, but 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 makeshift mask will catch the vast majority of infected droplets…which is a very good thing. As the health authorities have repeated, if you have Coronavirus, or believe you may have been exposed, 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 social distancing while creating a mass of potentially biohazardous materials; and
- Wearing a mask creates whole new mechanisms of transfer (and thus infection) and leads to issues with contact control.
Masks versus social distancing
The first is really easy to understand. If we feel that masks will protect us from airborne transmission, we’re more likely to reduce our attention to social distancing. We know social distancing works; any action that reduces it is bad.
But there’s also a second issue: if you are asymptomatic and using a mask to protect the public, that mask becomes a reservoir of viral material. If not replaced regularly it becomes a biohazard; if disposed of inappropriately, it poses a risk to anyone it comes in contact with (more on this later).
Mask provide a new mechanism of viral transfer
Now here’s the part that hasn’t been explained well, in my opinion. As noted above, asymptomatic mask wearers don’t just shed virus via airborne droplets, but also when the droplets hit surfaces. But what is not considered is these masks become viral reservoirs.
Cough a few times, and your entire mask is now covered in virus. Every time you touch that mask, your hands get re-infected. Since masks are uncomfortable, mask wearers tend to touch their face more. This negates a lot of the benefits of regular hand-washing.
Then we have the unaffected mask wearer. Sure, they are protected from direct transfer – but if they touch an infected surface, 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’s only for a short time. These masks are not designed to stop the migration of virus particles; the weave is too large and the virus too small. So if your mask gets exposed, 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. Your mask is only of use if you replace it regularly.
To put this another way, my kids love their vaporizers. They put in the aroma scent, and enjoy the vapours all evening.
Similarly, an infected mask becomes a vaporizer for Coronavirus until replaced. What’s worse, it becomes a new secondary reservoir of infected material – which as we’ve seen, then becomes a source of viral particles that helps defeat hand-washing.
But we aren’t done yet. One of the saddest parts of the asbestos story was the effect on the children of asbestos workers. Not only were the workers affected, but since the fibres got on their clothing, they brought the 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 homemade masks come home. If you’re using a bandanna as a mask ,you 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 transfer mechanisms 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. Another is ensuring clothing worn outside goes directly into the washer, not the hamper. But ultimately there are not enough masks to go around, and any re-used mask becomes a potential reservoir to re-infect users and their family members.
From my perspective, it’s easy to see where our public health officials are coming from. An individual not wearing a mask and practicing good social distancing runs a very low risk of direct inhalation, and avoids three other mechanisms of transfer (mouth-to-hand; hand-to-mask-to-hand; and mask-to-family member).
Moreover, since a makeshift mask provides little protection, and an infected mask runs risk of the vaporizer effect and also potentially reducing our desire to social distance – it’s easy to see why some health officials don’t recommend wearing masks.
Blair King is an environmental scientist who works out of Langley BC and blogs at the website A Chemist in Langley on the topic of evidence-based environmental decision-making.