On Feb. 10, the Centers for Disease Control and Prevention released new mask guidelines based on a study of how mask fit affects the wearer’s exposure to airborne particles. With more transmissible COVID-19 strains emerging around the world, it is important to properly use the right kinds of face masks.

Some practices – such as taking your mask off to speak or wearing your mask below your nose – are clearly problematic. Other mistakes may be less obvious. Everyone still needs to be wearing masks as much as possible – even if you’ve been vaccinated or have previously been infected with COVID–19. So how do you get the most out of a mask?

Mask materials

Your mask material is the most important consideration. Certain manufacturing techniques can make masks more efficient at filtering out the tiny droplets and aerosols that can carry the coronavirus.

During the past year, my graduate students and I at Binghamton University teamed up with scientists from the surgical robot company Intuitive Surgical and the Intuitive Foundation to test the effectiveness of different fabrics at filtering out airborne particles. Our work has been used by the CDC to inform mask guidelines.

Researchers believe that an infected person who talks expels droplets that can spread COVID-19 – especially in the 2- to 5-micron range, about 10 times smaller than the width of a typical human hair. One reason to wear masks is to catch these relatively big particles before they dry out and shrink into smaller particles, called aerosols, which linger in the air longer because of their diminished size.

For example, a 3-micron saliva droplet could shrink down to about 1 micron. Researchers think that droplets in the 2- to 5-micron range are most transmissive of COVID-19. This range is the sweet spot for droplets to linger in the air due to their small size, while still having a high probability of containing the virus.

N95 masks are the gold standard among lightweight respirators and are at least 95% effective at filtering out particles at 0.3 microns, well below the average size thought to dominate COVID-19 transmission. They are typically greater than 99% effective for particles 2 to 5 microns across. When leakage around the mask seal is taken into account, the performance typically drops to 90% to 95%.

KN95 masks, which have become more prevalent in the U.S. over the past few months, are the Chinese equivalent of N95 masks and are often the next best mask option in terms of performance. While KN95 masks often meet the N95 specifications, some researchers found their performance to be inconsistent in a study that has not yet been peer reviewed. The CDC maintains a list of internationally produced masks and their filtration performance that you can use to confirm the performance of masks before purchase.

Medical-procedure masks – specifically ASTM F2100-19, Class 1 masks, the blue papery ones you see everywhere – are typically made of several layers of meltblown nonwoven fabrics. If one had a perfect seal to your face, the material could filter out 95% of particles as small as 0.1 microns across. But these masks don’t seal all that well, and when you take into account the air leakage, filtration in typical usage drops to about 80%.

Cotton masks are among the most commonly worn and can also provide decent filtration. The filtration varies according to the tightness of the weave, and one study found that two layers of various widely available cotton fabrics filtered out between 34% and 66% of particles in the 2- to 5-micron range. This is good for catching particles from a person talking, but it won’t block small aerosols in the environment.

In our research, we tested a wide range of fabrics to see which worked best. Some samples were washed as many as 10 times with a variety of detergents and then retested for effectiveness. In our study, which is currently under peer review, we found the best combination was soft flannel on the inside for comfort, thin-as-possible cotton on the outside and an efficient filter in the middle.

Two masks are good, but make sure they fit

No matter how good a mask’s material is, it won’t work well if it doesn’t fit well. A lot of filtration efficiency is lost from leakage around the face mask, such as around the bridge of the nose or at the gaps between any facial hair and the mask. A well-fitting mask is one that seals tightly onto your face, ensuring that almost all the air you breathe goes through the filtering material rather than through gaps in the sides.

The CDC’s new guidelines are based on a study that tested ways to improve how masks fit – specifically double-masking and what they call “knotting and tucking.”

Double-masking is wearing a cotton mask over a medical-procedure mask. Knotting and tucking entails tying a knot in the elastic loops that go over your ears, close to where they attach to the mask. Then, you tuck the extra mask fabric into the gap that is often present where the ear loops attach to the mask, and flatten that part as much as possible. Both of these tricks to make a better fit decrease the mask-wearers’ exposure to potentially infectious aerosols by 95% as compared with wearing no mask at all. That’s a 15% improvement over the 80% efficiency found when using a single surgical mask.

DIY fit test

To get the best fit when using a mask, bend the metal nosepiece so that the mask tightly fits the curve of your nose. It is also important to make sure your mask fits beneath your chin and to remove any facial hair – air will take the path of least resistance through stubble rather than through the fine fibers of the mask.

Some places, such as hospitals and labs, do mask fit tests that are certified by the Occupational Safety and Health Administration. But these are impractical for home use. You can do your own qualitative fit test at home by lighting a citronella or other oil-scented candle and trying to smell it with and without a mask. The aerosols from a citronella candle are 0.01 to 0.02 microns across – much smaller than typical droplets from humans that would contain COVID-19. If you can’t smell the candle, or the smell is significantly reduced, you’re likely wearing your mask correctly.

Keep in mind, however, that this test is far from exact. For instance, cotton masks won’t filter out these tiny candle aerosols, but are still an important tool to block the majority of coronavirus droplets.

Making sure you are getting the most out of your masks is critical to slowing this pandemic. Double-masking or knotting and tucking, as well as using the right materials, can ensure that you and those around you are safer.

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Scott N. Schiffres, Assistant Professor of Mechanical Engineering, Binghamton University, State University of New York

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Trillions of barely visible pieces of plastic are floating in the world’s oceans, from surface waters to the deep seas. These particles, known as microplastics, typically form when larger plastic objects such as shopping bags and food containers break down.

Researchers are concerned about microplastics because they are minuscule, widely distributed and easy for wildlife to consume, accidentally or intentionally. We study marine science and animal behavior, and wanted to understand the scale of this problem. In a newly published study that we conducted with ecologist Elliott Hazen, we examined how marine fish – including species consumed by humans – are ingesting synthetic particles of all sizes.

In the broadest review on this topic that has been carried out to date, we found that, so far, 386 marine fish species are known to have ingested plastic debris, including 210 species that are commercially important. But findings of fish consuming plastic are on the rise. We speculate that this could be happening both because detection methods for microplastics are improving and because ocean plastic pollution continues to increase.

Solving the plastics puzzle

It’s not news that wild creatures ingest plastic. The first scientific observation of this problem came from the stomach of a seabird in 1969. Three years later, scientists reported that fish off the coast of southern New England were consuming tiny plastic particles.

Since then, well over 100 scientific papers have described plastic ingestion in numerous species of fish. But each study has only contributed a small piece of a very important puzzle. To see the problem more clearly, we had to put those pieces together.

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We did this by creating the largest existing database on plastic ingestion by marine fish, drawing on every scientific study of the problem published from 1972 to 2019. We collected a range of information from each study, including what fish species it examined, the number of fish that had eaten plastic and when those fish were caught. Because some regions of the ocean have more plastic pollution than others, we also examined where the fish were found.

For each species in our database, we identified its diet, habitat and feeding behaviors – for example, whether it preyed on other fish or grazed on algae. By analyzing this data as a whole, we wanted to understand not only how many fish were eating plastic, but also what factors might cause them to do so. The trends that we found were surprising and concerning.

A global problem

Our research revealed that marine fish are ingesting plastic around the globe. According to the 129 scientific papers in our database, researchers have studied this problem in 555 fish species worldwide. We were alarmed to find that more than two-thirds of those species had ingested plastic.

One important caveat is that not all of these studies looked for microplastics. This is likely because finding microplastics requires specialized equipment, like microscopes, or use of more complex techniques. But when researchers did look for microplastics, they found five times more plastic per individual fish than when they only looked for larger pieces. Studies that were able to detect this previously invisible threat revealed that plastic ingestion was higher than we had originally anticipated.

Our review of four decades of research indicates that fish consumption of plastic is increasing. Just since an international assessment conducted for the United Nations in 2016, the number of marine fish species found with plastic has quadrupled.

Similarly, in the last decade alone, the proportion of fish consuming plastic has doubled across all species. Studies published from 2010-2013 found that an average of 15% of the fish sampled contained plastic; in studies published from 2017-2019, that share rose to 33%.

We think there are two reasons for this trend. First, scientific techniques for detecting microplastics have improved substantially in the past five years. Many of the earlier studies we examined may not have found microplastics because researchers couldn’t see them.

Second, it is also likely that fish are actually consuming more plastic over time as ocean plastic pollution increases globally. If this is true, we expect the situation to worsen. Multiple studies that have sought to quantify plastic waste project that the amount of plastic pollution in the ocean will continue to increase over the next several decades.

Risk factors

While our findings may make it seem as though fish in the ocean are stuffed to the gills with plastic, the situation is more complex. In our review, almost one-third of the species studied were not found to have consumed plastic. And even in studies that did report plastic ingestion, researchers did not find plastic in every individual fish. Across studies and species, about one in four fish contained plastics – a fraction that seems to be growing with time. Fish that did consume plastic typically had only one or two pieces in their stomachs.

In our view, this indicates that plastic ingestion by fish may be widespread, but it does not seem to be universal. Nor does it appear random. On the contrary, we were able to predict which species were more likely to eat plastic based on their environment, habitat and feeding behavior.

For example, fishes such as sharks, grouper and tuna that hunt other fishes or marine organisms as food were more likely to ingest plastic. Consequently, species higher on the food chain were at greater risk.

We were not surprised that the amount of plastic that fish consumed also seemed to depend on how much plastic was in their environment. Species that live in ocean regions known to have a lot of plastic pollution, such as the Mediterranean Sea and the coasts of East Asia, were found with more plastic in their stomachs.

Effects of a plastic diet

This is not just a wildlife conservation issue. Researchers don’t know very much about the effects of ingesting plastic on fish or humans. However, there is evidence that that microplastics and even smaller particles called nanoplastics can move from a fish’s stomach to its muscle tissue, which is the part that humans typically eat. Our findings highlight the need for studies analyzing how frequently plastics transfer from fish to humans, and their potential effects on the human body.

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Our review is a step toward understanding the global problem of ocean plastic pollution. Of more than 20,000 marine fish species, only roughly 2% have been tested for plastic consumption. And many reaches of the ocean remain to be examined. Nonetheless, what’s now clear to us is that “out of sight, out of mind” is not an effective response to ocean pollution – especially when it may end up on our plates.

Alexandra McInturf, PhD Candidate in Animal Behavior, University of California, Davis and Matthew Savoca, Postdoctoral researcher, Stanford University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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