To the Editor,
Not wearing a mask in public is like double dipping the guacamole. It’s just not nice.
Two things to know about mask-wearing. First, your face covering protects others from your viral-laden respiratory droplets. Second, it decreases your risk of getting sick by about 65 per cent. The mask can reduce the amount of virus that you get in, so if you do get infected you have a lower dose with milder symptoms or no symptoms at all.
Masks mainly provide a physical barrier to respiratory droplets that are about one-third the size of a human hair. Those drops are one of the major ways the virus is transmitted. (Dean Blumberg, MD, chief of pediatric infectious diseases at UC Davis Children’s Hospital.)
Masks work. An international study that looked at which factors work best to reduce spread of COVID-19 identified three: (1) restriction of large gatherings of people, (2) school closures, (3) social distance (wear masks, keep six feet apart, restrict who you interact with). (“Impact of climate and public health interventions on the COVID-19 pandemic: a prospective cohort study,” CMAJ, July 2020.)
Three other studies analyzing COVID among health-care workers demonstrated that universal masking is associated with a significantly lower rate of COVID-19 transmission. (“Studies Track Infections to Measure Mask Effectiveness” – Medscape – Aug. 14, 2020.)
But even surgical masks are not airtight enough to create an effective barrier against much smaller aerosol particles, which are about 1/100th the size of a human hair. The best defence against aerosol particles is social distancing.
“Studies in laboratory conditions now show the virus stays alive in aerosol form with a half-life on the scale of hours. It persists in the air,” says William Ristenpart, PhD, a professor of chemical engineering at UC Davis. “That’s why you want to be outdoors for any social situations if possible.”
Many people have no symptoms and transmit the virus unwittingly so wearing a mask and keeping a distance are both critical.
Mask material. Studies that look at effectiveness of mask materials not surprisingly find denser fabrics and double layers better able to stop respiratory droplets. Felt and wool are too porous to stop respiratory droplets, and bandanas and neck fleeces actually increase spread of viral particles by breaking down larger particles into many smaller particles that stay airborne longer. Double layer fabrics are ideal. If you can blow out a candle with your mask on, it is not going to stop the spray of your viral-laden respiratory droplets.
Be socially responsible and kindly encourage others to do the same.
Dr. Nell Thomas