ORLANDO, Fla. – The omicron variant of COVID-19 has people rethinking how they protect themselves.
Some media stories are telling people to ditch their cloth masks and go straight for N95 respirators.
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While the N95 is a gold standard that will offer the wearer more protection from COVID-19 than other face coverings, some researchers say the mask that fits well and is comfortable to wear for each individual is the best -- and that may not be the N95 for you.
“There are multiple issues around masks,” said Prof. Steven Luby of Stanford University, one of the lead authors of a study on mask efficacy. “One is how well they actually filter and the other is how well they fit. So if they don’t fit very well then it sort of doesn’t matter how well they filter.”
Types of masks
We’ve also long been told by U.S. health officials that when a person wears a mask, they are protecting other people rather than themselves because the mask minimizes any particulates that get expelled when that person coughs or sneezes.
The N95 respirator is rated highly by the National Institute for Occupational Safety and Health for its performance in workplaces where workers are exposed to small particulate matter or viruses. The N95 actually offers some protection to the wearer.
At the beginning of the pandemic, concerns about PPE shortages led health officials to tell the public not to go out and buy masks, and then to use cloth masks or disposable surgical ones as they became more available, to conserve stocks for health care workers.
Now they are more available, but they are not for everyone.
The Centers for Disease Control and Prevention says the masks should not be worn:
- If you have certain types of facial hair
- If it’s hard to breathe
- If it’s wet or dirty
- With other masks
Luby said there isn’t much data right now on reusing an N95 mask, but points out that some medical professionals early in the pandemic often could use only one mask a day because of supply concerns, even though guidance had them changing out masks with every new patient examined.
“You have a mask for the day and you wear it for the whole day,” Luby said. “And you know, when you look at the amount of transmission that occurred using that approach, very little. I mean, health care workers who had good masks and practice good hygiene had very low transmission, so that says to me that we probably don’t need to change all the time.”
NIOSH says it does not recommend that medical workers reuse the N95s unless their facility is implementing crisis strategies. For the general public, NIOSH says people should follow manufacturer instructions.
“N95 respirators cannot be washed. They should be discarded when they are dirty, damaged, or difficult to breathe through,” a spokesperson for the agency said.
There’s another type of mask called a KN95 mask. Although it’s similar to the N95, it isn’t the same.
“So the KN95 is made in China and aspires to have the same filtration efficiency, but they have not been certified by U.S. NIOSH,” Luby said. “And CDC does have a site where they tested several different brands, and some of them did perform up to that standard, and others did not and so, so it’s less clear when you purchase these, whether you have one that is meeting that high standard or not. And I think that that’s something that’s just really hard for consumers.”
NIOSH said the KN95 masks are rated by an international standard, and manufacturers can ask NIOSH to rate them, but then they would be classified as N95 masks, not KN95.
The CDC also warns on its website that about 60% of KN95 masks sold in the United States are counterfeit and not approved.
Disposable medical procedure (or surgical) masks and cloth masks are more widely known and available to the general public. While not as effective as the N95 or similar masks, they do offer protection when used in a community setting.
Luby, a professor of infectious diseases, and his team conducted a large-scale clinical trial of more than 300,000 people in Bangladesh. Some of the subjects used cloth masks while the others used surgical masks. His team found that people who wore the surgical masks had significantly better efficiency than people who wore the cloth masks, even when the cloth masks had multiple layers -- 30% to 40% for the cloth masks.
“In contrast to the 90-plus percent that we would get out of medical-grade masks,” Luby said.
Even more surprising, Luby said the surgical masks still outperformed the cloth masks after they were washed.
“What we found in Bangladesh is that we could wash them with detergent, wash them and dry them and people could wear them. Wear them as much as a month in the trial,” Luby said. “And when you do that, when you get them wet, then you lose some of the filtration efficiency because some of that is based on charging of the spun polyester. But they still outperform even when washed, they still outperform the cloth masks.”
Luby said the masks were hand washed with a detergent similar to laundry detergent.
However, Luby said cloth masks still have been shown to interrupt COVID-19 symptoms.
“I’m not saying the cloth masks are worthless, but rather we got a strong signal on surgical masks,” Luby said.
He also points out that cloth masks tend to fit better for some people and again, that fit can make a difference.
How to get a good fit on your mask
NIOSH researchers published a study in the American Journal of Infection Control in December on mask efficacy and preventing the spread of infection.
The study focused on two areas that Luby agrees are important – filtration and fit.
The study concluded that a three-ply cloth mask over a medical mask (which is known as double masking), or securing a medical mask provided the best protection against particles from respiratory systems, outside of the N95.
This again goes back to the importance of a well-fitting mask in stopping those particles from getting through.
The study offered several options for improving the fit of the surgical mask, including adding a brace over the mask, using ear loop toggles, or knotting the ear loops. The study said crossing the earloops or putting a bracket under the mask did not increase performance.
“There’s still sort of an open question of how much is mask-wearing--that the people who have COVID are now wearing a mask and therefore we’re getting less COVID transmission, versus how much is that by wearing a mask I’m protecting myself,” Luby said. “And for example, the N95 is really designed to protect the healthcare worker. Yeah, but if we put surgical masks on patients, we also know for tuberculosis and other airborne diseases that that actually protects both healthcare workers and the community. So in some sense, when we’re putting this on, are we trying to optimally reduce shedding, or are we trying to protect ourselves? And I suspect that is some of both. And so that the better the fit, the more you’re actually forcing both inhalation and exhalation to go through the mask. And so that there are that many more opportunities to stop particles.”
What about filters?
“So the more that you can put between the air and between external and internal, the better. And so multi-layer masks tend to outperform single-layer masks, including those with inserts,” Luby said.
If you are keen to stick with a cloth mask and don’t want to double mask, the more layers that mask has the better. Some mask patterns, and some designer retailers like Very Bradley have sold two-layer cloth masks that come with a PM.2 filter that you can insert in between the layers.
There is not enough real data on filters in masks to determine if they are truly as effective.
A study published last summer in the American Chemical Society Nano found using polypropylene filters could potentially provide protection, but more research is needed.
Polypropylene is the same material used to make N95 masks, and filters made with polypropylene are available for sale.
The number of studies on masks as effective in warding off illness continues to grow. The EPA has an effectiveness study as well, and there are other studies published within the last six months. The CDC has the latest guidance on masks and choosing the right one on its website.
While not all face coverings are created equal, Luby says what matters is that people wear a mask, more than the type.
“I would much rather they put on a cloth mask than put on a surgical mask or put on an N95 and say ‘this is so darn uncomfortable. Forget it,’ and tear it off and go maskless,” Luby said. “So I think that people would protect themselves and protect their communities if they wore a mask. The better the mask, the more protection for them, the more protection for their community.”