Nobody should argue that face masks donāt provide protection, they do, especially indoors. I wouldnāt go into a shop without a surgical mask, but we should also be aware that most masks worn are of little use, and give a false sense of security.
The information in this Farmers Journal article is out of date and incorrect. The key issue to understand here is the difference between droplet transmission and airborne transmission. The WHO and CDC (based on the WHO) claimed from March onward that transmission was droplet. This was based on a study from China that there was no evidence of airborne transmission. The same lads who were claiming in late January there was no evidence of human to human transmission.
The CDC changed itās guidance in early October and said Covid 19 can be spread by airborne transmission and people can be infected by someone infected more than 6 feet away. This should already have been obvious given the respective R0 of the regular flu and Covid 19, the regular flu is 1.3 and it was known that Covid-19 was at least 3 and maybe 5 or 6 back in February. Flu is transmitted mainly by droplets, the R0 for Covid-19 puts it firmly in the airborne category. In terms of transmission, it is probably closer to measles (R0 >12) than influenza. This is a highly infectious virus, which makes stopping itās transmission extremely difficult and maybe impossible in western countries.
What has this got to do with masks? Particles come in all sizes, large droplets expelled when you sneeze are 10 - 2,000 micron, aerosols produced by speaking and even breathing are in the range 300 nm to 5 micron. A person who is infected transmits 1,200 aerosol particles for every droplet. Aerosol particles stay in the air for long periods, so indoors with poor ventilation there is a very high risk of getting infected if someone infected is or was in the room. Aerosol particles can linger in poorly ventilated areas for hours.
The type of mask is critical. A surgical mask fitted with no gaps has 99% filtering efficiency for particles 300 nm to 5 micron, but drops to 50% even with a 1% gap. There is a reason why hospitals here wonāt let you in the door with a cloth mask and insist on you wearing a surgical mask that they provide. A tightly woven cotton mask (600 TRI) is almost as good as a surgical mask, but a porous cotton mask is only 10%. The assorted rags, scarves, and most cloth masks you see people wearing are in the latter category.
Bullet point: Wear a surgical mask or a tightly woven cotton mask, especially indoors, and make sure it is a tight fit to your face.
