Hello. I'd like to talk to you about the decision to give out cloth masks at Zcon. All of the evidence shows that N95+ masks (as defined below) are substantially more effective.
It hadn't even occurred to me when arguing for mandatory mask wearing that I needed to argue specifically for N95+ masks over cloth masks, because I thought this was well known.
Why is ZF spending money on customizing masks that are inadequate to keep us safe?
Definition: an N95+ mask is a mask that filters out at least 94% of particles 0.3 microns (0.3 μm) or above. This includes FFP2 masks (the European equivalent of N95) and N99 or FFP3 masks (which provide at least 98% filtration of partices 0.3 microns or above).
―What Are the Differences between FFP3, N95, And Surgical Masks? October 2021.
Early in the pandemic (before mid-2020), there was insufficient evidence to say whether or not COVID was spread mainly by large droplets (most of which would fall to the ground relatively quickly), or by microdroplets that can persist for long periods as aerosols. The latter is called "airborne transmission". However, it was definitively resolved quite early on that COVID-19 does spread primarily through airborne transmission (see for example this article from New Jersey COVID-19 Information Hub in September 2020).
There was considerable political resistance to making this point clear to the wider public or even to front-line health workers, but it was not scientifically in doubt among competent epidemiologists after, at the latest, the end of 2020.
The critical point in reducing transmission of an airborne viral disease through mask wearing, is to make sure that microdroplets containing virus particles are caught by the mask. This can be either the mask of the infected person as they breathe out, or the mask of the potential infectee as they breathe in. (The reason why N95+ masks are multi-layer is to attempt to stop any caught virus particles from migrating through the mask, at least until those particles are no longer infectious.)
It typically takes between a few hundred and a few thousand inhaled virus particles to catch COVID. Estimates of how long airborne virus particles retain their ability to transmit COVID vary from around 20 minutes to three hours. Virus particles caught by a mask stay infectious for about the same time unless the mask is impregnated with antivirals (which most masks are not). The time for which microdroplets remain in the air also varies from minutes to hours, depending on their size and on air movement.
Because cloth masks normally have a single, somewhat permeable layer, they are much less effective at keeping virus particles that are caught when inhaling from infecting the wearer. They are also less effective at catching particles that are breathed out by an infected person. This is because they are usually less closely fitted, and because many particles are small enough to just go through the mask.
It is known that respiratory protective equipment is only effective when there is an adequate seal formed between a mask and the person’s face to ensure that inhaled air is actually filtered. Indeed, research has suggested that an ineffective seal is the primary cause of airborne contamination amongst wearers of face masks [3]. It has been noted that leakage around the face mask may account for a third of airflow across surgical masks and a sixth of the flow across respirators [3]. Fit is recognized as being particularly important when determining whether masks are capable of reducing the spread of fine particles.
The following studies compare the effectiveness of N95+ vs cloth masks:
- A comparison of performance metrics for cloth masks as source control devices for simulated cough and exhalation aerosols. Aerosol Science and Technology, May 2021
That is, the filtration effectiveness of cloth masks varies over a wide range, and cannot be relied on. (The "cloth mask" that reached 98% filtration efficiency in this study was not a typical example of a cloth mask, it just wasn't certified as an N95.)Collection efficiencies [of ≤7 micron particles] for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. Filtration efficiencies for the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on headforms and 1.0 to 4.0 on human subjects.
- Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021
Wearing an N95/KN95 respirator (aOR = 0.17; 95% CI = 0.05–0.64) or wearing a surgical mask (aOR = 0.34; 95% CI = 0.13–0.90) was associated with lower adjusted odds of a positive test result compared with not wearing a mask (Table 3). Wearing a cloth mask (aOR = 0.44; 95% CI = 0.17–1.17) was associated with lower adjusted odds of a positive test compared with never wearing a face covering but was not statistically significant.
Individually sealed N95+ masks are available at a cost per mask of about 1 USD. The conference lasts for three days, so providing three masks to each attendee is affordable.
Hell, I'd pay for all the masks myself if that were the obstacle to changing the policy. ―Daira Hopwood
By distributing customized cloth masks, ZF is implicitly encouraging attendees to wear those masks, both during and after the conference. Someone wearing a cloth mask is normally not wearing a more effective mask.
Technically, it's possible to wear the cloth mask over an N95+ mask, but please do not encourage people to do that either. It just obscures that an N95+ mask is being worn, which has two disadvantages:
- it is important that N95+ masks are visibly worn in order to reduce social resistance to doing so;
- clinically vulnerable or otherwise COVID-wary attendees need to be able to see that people they're close to are wearing effective masks.
If attendees want to customize their N95+ masks then they can use a non-toxic marker pen to draw Zcash logos or zebras or whatever on them. That doesn't impair the effectiveness of the mask in any way, nor does it obscure that an effective mask is being worn. It also showcases the attendee's creativity! Ⓩ 🦓 🙂
Since N95+ masks are just as comfortable to wear as surgical masks (in my experience, more so for at least some brands), the evidence shows they are more effective, and it is still quite affordable to provide several N95+ masks to all attendees, I'm not sure what the argument would be for providing surgical masks.
Attendees should be strongly encouraged to test for COVID before coming to registration, and in fact before travelling. I don't object at all to providing additional lateral flow tests at registration, but it's not ideal that people are potentially exposing other attendees while not already having tested themselves.
I'm disappointed that the decision-making process over COVID protection has not been a more interactive process that involved people most affected by the decision, i.e. clinically vulnerable attendees.
I am proud of the Zcash community's emphasis on and respect for scientific rigour. I would hope that this extends to evidence-based public health policy and is not limited to cryptography and distributed systems.
I don't know whether this will be a factor at all, but ZF might be reluctant to appear to change its mind twice over COVID policy. If that is an issue, it is one entirely of ZF's own making, since it could have just asked clinically vulnerable attendees what we thought about cloth masks rather than presenting the decision as a fait accompli.
I do want to thank you for taking on board the feedback about the COVID-wary badges.
I hope that we are involved at a much earlier stage for future events including Zcon4, since it seems likely (given the capacity of the SARS-CoV-2 virus to evolve and the continuing failure of governments to institute adequate public health measures) that the pandemic will still be in full swing in 2023.