To Mask Or Not To Mask? — Dr Tan Poh Tin

By CodeBlue | 25 May 2020

My mask protects you, your mask protects me, our masks protect others.

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We have a few weeks before our kids return to school and kindy, and all to work. Should we and our children still wear masks in public places?

Surgical masks at RM1 to RM1.50 each may be burdensome for the average family to sustain long term. Are DIY cloth masks good alternatives? Which material works best?

As a public health specialist and paediatrician, I have summarised the current scientific findings to help you decide. As Covid-19 is a new virus and much research is ongoing, recommended “good” practice may change with new publications and as the epidemic curve flattens or gets worse. Speak to your doctor or “google” to keep up to date with latest guidelines.

Be reminded that masks must be used in conjunction with other preventative measures i.e. good respiratory etiquette, regular and frequent hand hygiene, self-isolation when unwell and avoiding crowded and noisy places (with people talking or shouting).

Both the American Academy of Pediatrics and CDC strongly advise against masks for children below 2 years, (especially babies), because of the high risk of suffocation.

Universal wearing of masks in public areas have reduced Covid spread in countries, like Taiwan. Taiwan did not lockdown but efficiently implemented all the strategies — Test, Trace, Isolate, Treat (early), Social Distancing, Hand Wash and compulsory face masks. To date, they have only 440+ cases and seven deaths after testing almost 70,000 (population 24 million).

“Mouth and nose lockdown” to minimise community transmission is more sustainable than “full body lockdown” from economic, social and mental health standpoints.

Your mask protects me and my mask protects you from the germ-loaded mucous and saliva droplets expelled as we talk, laugh, sing or sneeze. During surgery, a surgeon wears a surgical mask so that his droplets/aerosol will not contaminate the wound. The mask also reduces the risk of patient’s body fluids, saliva or blood from splashing onto his mouth and nose (and if he wears eye protection, eyes).

Masks, even homemade cloth ones, have been shown to trap exhaled droplets and help reduce contamination of the environment and fomites where these droplets settle.

Studies of healthy volunteers wearing homemade mask, surgical mask, or no mask showed that both masks significantly reduced the number of microorganisms expelled when they coughed.

Compared to homemade masks, surgical masks were 3x more effective in blocking outward transmission to others and 2x better in preventing inward passage of germs to wearer. To prevent droplet transmission from infected individuals, home-made masks should only be a last resort, but it would be better than no protection.

Surgical masks are made from non-woven polypropylene melted and blown onto a conveyor in a web. As the strands cool, they bond with each other. This material is able to block microorganisms smaller than 25nm (coronavirus is 3x bigger and can be filtered out).

Surgical masks are less efficient for inward protection because of the leak around the edges. Hence, health care workers handling Covid cases must wear N95 respirators. This must be test fitted for each wearer.

To protect from inhaling infectious particles, the seal should be so tight that one can still breathe through it but cannot smell anything. The USA standard N95 mask blocks 95% of aerosols or viruses if properly fitted. Protection drops when this seal is not tight, as with people with facial hair or when the correct size mask is unavailable.

N95 should be reserved for health care workers and front-line Covid responders.

Two of the three high school students who collapsed and died during intense running or physical exercise in China in April 2020 were noted to be wearing N95 equivalent masks.

Although autopsy reports for the sudden deaths were not available, the current advice is against wearing high-grade medical ones (N95) during strenuous exercise or gym as these tightly fitted masks may impede the oxygen supply and carbon dioxide removal.

Wearing a mask while driving alone in the car is also not recommended. A US man who lost consciousness while driving and ran into a pole was noted by police to have been wearing an N95 mask. He was not under the influence of alcohol or drugs.

Although his preexisting medical condition was not known, it was thought that the wearing of a N95 mask over a prolonged period could have contributed to his loss of consciousness.

How well do household materials block bacterial or viral aerosols?

Anna Davies et al (“Testing the Efficacy of Homemade Masks: Would they protect in an Influenza Pandemic” August 2013 in Disaster Medicine and Pubic Health Preparedness) showed that all materials show some capability to filter microbial aerosol.

The Filtration Efficiency for bacteria (0.95-1.25 micron) were linen 60%, silk 58%, 100%-cotton T shirt 69%, tea towel 83%, antimicrobial pillow case 65% (surgical mask 96%).

Tested for bacteriophage (viral particle 23 nm) the filtration efficiencies were still surprisingly high — linen 62%, silk 54%, 100% cotton 51%, tea towel 72%, antimicrobial pillow 68% (surgical mask 90%).

Even a simple scarf can block 62% of bacteria and 49% virus RNA (could be useful if you are caught in a crowded closed place without a mask!!)

Doubling the layer of tea towel increases filtration to 96% for bacteria, or cotton 70%. Vacuum cleaner bags have been found to be as effective as surgical mask, 94% and 86%, but are harder to breathe through, forcing air to escape around the mask.

The antimicrobial pillowcase and 100% cotton T-shirt were found to be most suitable for DIY masks. T-shirt material has the added advantage of being stretchy for better fit and less leak.

Doubling the fabric improve the filtration slightly, but breathability affects long-term use. Avoid using old fabrics because washing and drying may stretch the pores and allow more particles to get through.

Paper towels have been tested and found to capture 23% of particles 0.3 microns or larger if single layer, and 33% if doubled.

One report claims that an extra outer lining with nylon stocking to a DIY cloth mask may improve filtration.

Face masks reduce aerosol exposure by a combination of filtration action of the fabric and the seal between the face and mask. If masks are uncomfortable, wearers may remove them to cough, sneeze or wipe their eyes or nose. This will cause increased transmission.

Decontaminating masks for reuse

DIY cloth masks have to be washed in the washing machine or with soap and hot water or dilute bleach and dried in the sun.

Where surgical masks are limited, they can be slipped in between the layers of DIY mask for longer reuse. The best strategy to kill the germs on these is to put the mask in a paper bag and leave it for seven days.

Some HCW (health care workers) leave the paper bag with mask in the parked car and let the heat from the sun kill the virus on the mask. Plastic bags are not used because the mask may collect moisture leading to bacterial contamination.

Some have suggested washing surgical masks, but this may affect efficacy. Surgical masks are meant for single-use, so in a high-risk environment, all these recycling measures are not recommended.

In times of shortage, N95 respirators can be decontaminated and re-used for up to three times for UV and Vaporised Hydrogen Peroxide, and up to two times for dry heat (70°C).

N95 masks decontaminated with 70% ethanol spray did not function effectively after decontamination. Alcohol and bleach interfere with electrostatic charges in the N95 mask, which is part of the filter, so they should not be used.

The take-home message is 25% of infected Covid-19 persons are asymptomatic throughout. Most patients may not show symptoms in the first 5-6 days of infection, but can infect others.

By wearing masks, infected persons can trap much of the infective droplets and protect others and the environment. Start making masks to give to those who cannot afford to buy any. Their wearing masks protect you.

We can protect ourselves from breathing in aerosols especially in crowded places, public transport or in classrooms where we cannot stay out of range of their droplets! Surgical mask is best, but any mask is better than none.

If four out of five wear masks, we can block the virus from leap-frogging and prevent the next Covid tsunami. Keep washing hands, frequently, for at least 20 seconds with soap and water.

Dr Tan Poh Tin is a Consultant Pediatrician and Public Health Specialist who served in the Sarawak Health Department as Divisional Medical Officer of Kapit and Sibu Divisions in the 80s and State Pediatrician early 90s. She retired as Associate Professor from the UNIMAS Medical School to private practice. Her passion is to simplify medical information and help people learn.

  • This is the personal opinion of the writer or publication and does not necessarily represent the views of CodeBlue.
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