Why face masks are an easy answer to the covid Growth Factor

July 19, 2020

In our April blog we discussed the top four reasons for wearing a face mask.

They were:

• The mask acts as a barrier to droplets passing between one person and another.

• The mask prevents the wearer from touching their nose and mouth

• The lower the dose (inoculum) of virus which you might be exposed to by wearing a mask, the better chance your body can mount a defence

• The mask is a visible signal to others that virus transmission prevention is a priority and is becoming a social norm in the current circumstances.

In this new blog we reinforce the message about wise mask wearing by including references to more detailed work that is being done regarding the mitigation of the transfer of the disease.

This article is written at a time when our home State of Victoria, Australia, is experiencing a spike in new cases after quite a long period of control where reopening the State was a real prospect. But as we are all finding out, Covid 19 is a very difficult disease to control as it is especially contagious and can be carried by people who are not experiencing any symptoms.

As a general guide of whether the coronavirus outbreak is getting better or worse is the growth factor.

The common way to calculate this is to divide the number of new cases in the last week by the number of new cases of the week before.

• If the growth factor is above one, the number of new cases each day is going up. If it stays above one consistently, alarm bells should be ringing.
• If it’s below one, we’re getting (or keeping) the outbreak under control.

While most of Australia is running under 1.0 Victoria is currently running at over 2. So to halve the number every tool in the tool box needs to be used.

One of the favoured forms of mitigation is Social Distancing as the further away you are from others the less chance there is of the virus being carried from one to another.

There have been various studies measuring how far the virus could pass through the air as well as how long the virus could remain in the air. And as described later outcomes are affected also by mask wearing.

Visually particle distribution looks a bit like the picture below although the sizes of dots have been exaggerated for effect. Considering human hair is roughly 80 micrometers thick, the droplets range in size from roughly 5 micrometres to 500 micrometers.

The biggest droplets get pulled by gravity to the floor within a couple of meters whereas smaller droplets pass into the air and the water carrying the virus evaporates quite quickly leaving the virus in aerosol form (droplet nuclei) to hang in the air for an estimated 3 hours.

It is unclear how much of the aerosol is needed to infect an individual. And of course air does not usually remain still, especially outside as can easily be seen when you are breathing out on a cold Melbourn morning. But of course in a confined space such as an elevator, office or small room without effective ventilation the aerosols could linger for a long time and the amount of aerosol in the air could become significant.

To mitigate viral aerosol creation and inhalation wearing a mask can be very effective.

One study which simulated aerosol transfers under different mask wearing conditions, ie type of mask demonstrated that droplet and aerosol distribution distances can be reduced to 10-20 centimetres down from 3-4 metres. In addition the amount of droplets captured in the mask means that the total quantity in the air would be much less as well.

Against the need to halve the Growth Factor in Victoria, dramatically reducing the amount and likelihood that the virus can be transmitted becomes a must to sensibly wear masks.

There are some downsides to wearing masks but these are few and can be mitigated.

The major concerns are:

1) The mask itself if contaminated with the virus can be a source of contamination. This is true but can be mitigated by taking proper precautions when taking the mask off, such as placing it in a plastic bag for later sensible disposal or washing. And as always wash your hands after handling the used mask.

2) The mask makes it hard to breathe. This is true to varying degrees depending on the quality of the mask. It is likely that the more difficult masks to breathe through are the ones providing greatest protection, however a mask that is too restrictive can increase the chance of air being dragged in and out via the edges of the mask..

So provided a person's likely exertion rate is taken into account in the context of the environment that they will be wearing the mask then a fair compromise can be made. For example wearing a heavier mask in situations where close encounters for extended periods with others is likely such as on public transport, or in classrooms. A lighter more breathable mask would be suited for walking or cycling in the open air.

3) Single use masks are increasingly becoming an environmental concern because they are not being disposed of properly. This can be solved by wearing a reusable mask and having a sensible washing routine. The virus is susceptible to simple soap and warm water (30C+ would be best). It has even been suggested that leaving a reusable mask on the dashboard of a car parked outside after use exposes it to sufficient Ultra Violet light (not all UV is prevented from traveling through glass). This strategy would be most effective in Summer months where the natural heat of the car interior would also affect the virus.

4) You can't smile with a mask on. Amazingly this is not true. You can still smile and importantly the set of muscles most important to validating that your smile is sincere are the obicularis occuli which encircle our eye sockets.

And did you know that we automatically mimic the smile of others, to feel ourselves whether it is fake or real. If it is real, our brain will activate the same areas from the smiler and we can identify it as a real one.

So all you instagrammers, remember it's still important to smile even when you are wearing a mask.

But seriously, with the Growth Rate needing to be slashed, NOW is the time to be wearing face masks!

Taking these thoughts to their natural conclusion ArmaSkin has made available for its customers, a heavy duty four layer merino wool ArmaSkin Face Mask, for details see www.armaskin.com