I didn't realise how THIN the research advice was, which the UK government was receiving from SAGE
https://assets.publishing.service.gov.u ... age-48.pdf
NERVTAG/EMG - emerging virus threats grouping, paper on the role of "aerosol transmission" of Covid-19, dated July 23, considered by SAGE, the day before mask wearing became "mandatory" in indoor settings.
the paper was the best assessment of the evidence at the time of writing.
Assuming, for the sake of argument, that virusus can survive on water and spread through the air [lol!]
Most types of cloth face coverings and masks are likely to provide some benefit as
a source control against both larger droplets and small aerosols. Small aerosols (<10 µm) that carry
virus and can remain airborne in the air in a room may start life as much larger respiratory droplets
(>10 µm). These evaporate when they leave the mouth and are exhaled into the less humid air in an
indoor environment. Studies suggest that the final size of an aerosol which has evaporated is around
20-40% of its starting diameter depending on the humidity[22]. Hence, a 30µm droplet in a dry
environment could evaporate to become a 6 µm aerosol. Although a cloth face covering or surgical
mask is not likely to be effective at trapping small aerosols, they are likely stop these larger droplets
that would go on to become the small aerosols as there is no time for them to evaporate. As such,
they are likely to reduce the source of both larger droplets and small aerosols. Face coverings and
masks will be less effective at preventing the release of smaller aerosol particles that are less than 5
µm when exhaled. A study of the influence of surgical facemasks on exhalation from people with
influenza shows a 25-fold reduction in aerosols >5 µm and a 2.8-fold reduction for aerosols <5
µm[23]. An unpublished PHE study considering the reduction effect of masks against exhalation of
oral bacteria when coughing shows cloth face masks to be as effective as surgical masks. A report of
lack of transmission from two COVID-19 infected hairdressers in the US to 139 clients in a hair
dressing salon, when both the stylists and clients and wore facemasks/coverings [24] is evidence of
the potential benefit of these in reducing transmission ***. Similarly, there is anecdotal evidence that
nosocomial transmission of COVID-19 has reduced since the extended use of facemasks by
healthcare workers was implemented in hospitals in England and the US [25]. However, in both of
these cases it is not clear whether transmission is through droplets or aerosols.
As protection for the wearer: Face coverings are likely to provide some protection for the wearer
from exposure to large droplets via the nose and mouth, but are unlikely to reliably protect against
the inhalation of small aerosols although laboratory studies show they may have a small effect
*** lol! and this is being cited, 2020, as the most recent piece of evidence to government?
Seems like the purpose of the mask is to make sure the wearer is continuously breathing in a nice moist cocktail of bacteria.
As current evidence suggests that the highest likelihood of aerosol transmission, outside of high risk
clinical spaces, is from an asymptomatic infector in a poorly ventilated space, enhanced use of face
coverings in indoor spaces is recommended. Face coverings are not usually in scope of personal
protective equipment (PPE) regulations, which has meant that there has been no standard against
which performance can be checked. However, recent work by CEN, the European Committee for
Standardization, has produced a guide to community face coverings (CWA 17553:2020) which
specifies the minimum requirements for reusable or disposable community face coverings and
materials intended for the general public, including adults and children aged 3-12 (when being
supervised by an adult)
In their own words - more research needed.
Job done, based on essentially no hard science, and the bio-terrorists of the asyptomatic carrier.
