Recently, a doctor said on Twitter that now that there isn’t a shortage of surgical masks or N95 respirators, people should prefer them over cloth masks.

cloth masks hanging for drying Image for representation. congerdesign/Pixabay
Coronavirus Coronavirus Wednesday, October 21, 2020 - 18:41

Masks became quite the necessity for a good part of this year, and will continue to be for several coming months at least. They have also become an accessory, with every other retailer selling them – with quirky prints, boasting of multiple layers, maximum filtration, reusability and so on. Recently though, a doctor named Faheem Younus tweeted that the efficacy of cloth masks was poor and people should go back to using surgical masks or N95 masks now that the latter are not in shortage.

“Cloth masks/bandanas were recommended due to low supply. Governments should now recommend surgical masks/KN95 for people in crowded places. Shun cloth masks. Their efficacy — like the valved masks — is poor. People may reuse surgical masks/KN95,” he said.

But is this really true? Do even those who are not health workers, or in close proximity with COVID-19 patients or working at the frontlines also need surgical masks or N95 masks? TNM asked some experts.

What determines efficacy of cloth masks?

Dr Sundeep Salvi, Director of Pulmocare Research and Education Foundation (PURE), based in Pune, says that depending on material, layers and make, different cloth masks have different filtering capacity from 50-60% to even over 90% depending on threads per inch (TPI), number of layers, as well as the fabric used in those layers.

“A higher number of layers are not necessarily good, because it could make the mask uncomfortable or cause difficulty in breathing. It is, however, possible to increase filtration to 90% and above if the TPI count is above 400 to 600, and if there are chiffon or silk layers in the cloth mask.

A study published in April 2020 found that cotton and chiffon blend provided protection up to 97% from particles that are less than 300 nanometres in size, like the SARS-CoV-2 – almost at par with a properly worn N95 mask. Further, a cotton quilt material provided 96% protection, while two layers of a cotton material with 600 threads per inch would provide 82% protection, the study, called ‘Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks’ added.

Dr Shahid Jameel, a virologist, also suggests that a good way to judge a mask’s efficacy is to see if light passes through it. “Two or three ply or layer cloth masks are fine for the general public. If light passes through, it probably needs another layer.”

Read: Which material works best for a home-made mask? This and more answered by an expert

“To examine the filtration efficacy of the different kinds of layered cloth masks in the market right now, we need research labs to be set up by the government at the regional as well as national levels,” Dr Sundeep says. He also emphasises that the reason to wear masks is not to protect oneself as much as to prevent droplets with the virus escaping from yourself if you have COVID-19. “Therefore, to protect yourself, you need to ensure that the person(s) in front of you are also wearing masks.”

Exposure determines filtration required

Both Dr Sundeep and Dr Shahid say that for the community, it is okay to wear cloth masks as opposed to surgical masks or N95 masks. “The virus is not simply around us, it is in droplets. Therefore, cloth masks that have at least two layers should be able to provide good enough protection against transmission,” Dr Shahid says.

Both Dr Shahid and Dr Sanjiv warn that a lot of masks being sold are single layer cotton masks, which are not enough. Dr Sanjiv also contests that any mask made of cotton alone is enough. “Cotton essentially absorbs moisture, which does not bode well for protection at this point. The global standard for any surgical gowns or masks is a fabric that is a blend of 67% cotton and 33% polyester. Any layered mask should ideally have a melt blown fabric layer.” Melt blown fabric is a non-woven sheet made from plastic that works as a filter material in masks.

However, Dr Sundeep and Dr Sameer Agarwal of Rajasthan-based Practicing Pathologists Society say that the type of adequacy of the type of mask is also determined by the exposure that a person has to the virus. “So, while it is ok to wear a layered cloth mask while going to buy vegetables, a surgical mask would be needed while going to a hospital. If I am going to see a patient, and if I have to perform a procedure in their mouth or nose, the risk of exposure is higher, I would need to wear a tight-fitting N95 mask,” Dr Sameer says.

However, experts also say that it does not make sense for everyone to switch to N95 masks, because not only are they expensive, but they are not high on comfort and can be difficult to breath in. “Comfort is an important factor given the varying temperatures in different parts in our country to ensure that people wear masks uniformly,” Dr Sameer says.

Many experts insist that it is crucial to bring in regulation. Though masks have been classified as a ‘drug’ under the Medical Devices (Amendment) Rules, 2020 that came into effect earlier this year, seemingly to bolster quality control, no regulations have been announced. Further, the Central Drugs Standard Control Organisation (CDSCO) relaxed the requirement for licensing and registration by mask manufacturers till September 1, 2021. This has resulted in a buffer period till September next year wherein manufacturers can make masks in a vacuum of norms, points out Dr Sanjiv, Chairperson of the Preventive Wear Manufacturers' Association of India (PWMAI).

The virus transmits via droplets

It is important to remember that the novel coronavirus transmits through droplets. So, even though any cloth mask has ‘spaces’ in it, it does not necessarily mean that the SARS-CoV-2 virus can pass through. This article by three epidemiology experts notes that the virus is about 0.1 micrometer in diameter, and the holes in a woven cloth viewable by the naked eye could be five to 200 micrometers in diameter. When we sneeze or cough, the droplets potentially containing the virus released could be of a range sizes. However, while there are gaps in the mask, the threads are usually wider than the gaps. “The particle is not like a mosquito, which can redirect itself to avoid obstacles,” the article says. A mask having multiple cloth layers adds to this protection – so while some particles could pass through, some will be contained.

Dr Sanjiv argues though, that masks that are single layer or just made of cotton may not cut it in the next few months, especially in north India due to the air pollution due to the festive season. “Because the virus is on droplets, the smog and fog will give it a medium to exist on in the air.”

While it can be difficult to gauge the efficacy of a cloth mask in the absence of standards and a plethora of options, even if the community wears cloth masks that are 50-60% effective, it can have a significant impact on reducing transmission, Dr Sundeep says.

study done in Washington and New York in the US and published in April found that hypothetically, immediate 80% adoption of masks that are moderately (50%) effective could prevent 17-45% of the projected deaths in New York over two months, while reducing the daily death rate by 34-58%. Even masks that are only 20% effective were found to be useful in reducing transmission. “80% adoption of such masks could reduce mortality by 24-65% (and peak deaths 15-69%), compared to 2-9% mortality reduction in New York (peak death reduction 9-18%),” the study, called ‘To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic’, found.

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