Why There Can Never Be an Empirical Test of a Nation-Wide Mask-Wearing Policy
…no study exists that shows a benefit from a broad policy to wear masks in public. There is good reason for this. It would be impossible to obtain unambiguous and bias-free results [because]:
Any benefit from mask-wearing would have to be a small effect, since undetected in controlled experiments, which would be swamped by the larger effects, notably the large effect from changing atmospheric humidity.
Mask compliance and mask adjustment habits would be unknown.
Mask-wearing is associated (correlated) with several other health behaviors; see Wada (2012).
The results would not be transferable, because of differing cultural habits.
Compliance is achieved by fear, and individuals can habituate to fear-based propaganda, and can have disparate basic responses.
Monitoring and compliance measurement are near-impossible, and subject to large errors.
Self-reporting (such as in surveys) is notoriously biased, because individuals have the self-interested belief that their efforts are useful.
Progression of the epidemic is not verified with reliable tests on large population samples, and generally relies on non-representative hospital visits or admissions.
Several different pathogens (viruses and strains of viruses) causing respiratory illness generally act together, in the same population and/or in individuals, and are not resolved, while having different epidemiological characteristics.
Unknown Aspects of Mask Wearing
Many potential harms may arise from broad public policies to wear masks, and the following unanswered questions arise:
Do used and loaded masks become sources of enhanced transmission, for the wearer and others?
Do masks become collectors and retainers of pathogens that the mask wearer would otherwise avoid when breathing without a mask?
Are large droplets captured by a mask atomized or aerolized into breathable components? Can virions escape an evaporating droplet stuck to a mask fiber?
What are the dangers of bacterial growth on a used and loaded mask?
How do pathogen-laden droplets interact with environmental dust and aerosols captured on the mask?
What are long-term health effects on HCW, such as headaches, arising from impeded breathing?
Are there negative social consequences to a masked society?
Are there negative psychological consequences to wearing a mask, as a fear-based behavioral modification?
What are the environmental consequences of mask manufacturing and disposal?
Do the masks shed fibers or substances that are harmful when inhaled?
Conclusion
By making mask-wearing recommendations and policies for the general public, or by expressly condoning the practice, governments have both ignored the scientific evidence and done the opposite of following the precautionary principle.
In an absence of knowledge, governments should not make policies that have a hypothetical potential to cause harm. The government has an onus barrier before it instigates a broad social-engineering intervention, or allows corporations to exploit fear-based sentiments.
Furthermore, individuals should know that there is no known benefit arising from wearing a mask in a viral respiratory illness epidemic, and that scientific studies have shown that any benefit must be residually small, compared to other and determinative factors.
