Face masks during the COVID-19 pandemic...that's found the number of microscopic particles that leaked to the inside of the homemade masks were twice that of commercial masks

During the COVID-19 pandemic, face masks, such as surgical masks and cloth masks, have been employed as a public and personal health control measure against the spread of SARS-CoV-2. In both community and healthcare settings, their use is intended as source control to limit transmission of the virus and personal protection to prevent infection. Their function for source control is emphasized in community settings.

The use of face masks (or coverings in some cases) has been recommended by American immunologist and NIAID director Anthony Fauci to reduce the risk of contagion. In the COVID-19 pandemic, governments recommend the use of face masks with a main purpose for the general population: to avoid the contagion from infected people to others. Masks with exhalation valves are not recommended, because they expel the breath of the wearer outwards, and an infected wearer would transmit the viruses through the valve. A second purpose of the face masks is to protect to each wearer from environments that can be infected, which can be achieved by many models of masks..Between the different types of face masks that have been recommended throughout the COVID-19 pandemic, with higher or lower effectivity, it is possible to include: cloth face masks surgical masks (medical masks) uncertified face-covering dust masks certified face-covering masks, considered respirators, with certifications such as N95 and N99, and FFP filtering respirators with certifications such as N95 and N99, and FFP other respirators, including elastomeric respirators, some of which may also be considered filtering masks There are some other types of personal protective equipment (PPE), as face shields and medical goggles, that are sometimes used in conjunction with face masks but are not recommended as a replacement. Other kinds of PPE include gloves, aprons, gowns, shoe covers and hair covers. A cloth face mask is worn over the mouth and nose and made of commonly available textiles. Masks vary widely in effectiveness, depending on material, fit and seal, number of layers, and other factors. Although they are usually less effective than medical-grade masks,[citation needed] some health authorities recommend their use by the general public when medical-grade masks are in short supply, as a low-cost and reusable option. Unlike disposable masks, there are no required standards for cloth masks. One study gives evidence that an improvised mask was better than nothing, but not as good as soft electret-filter surgical mask, for protecting healthcare workers while simulating treatment of an artificially infected patient. Research on commonly available fabrics used in cloth masks found that cloth masks can provide significant protection against the transmission of particles in the aerosol size range, with enhanced performance across the nano- and micronscale when masks utilize both mechanical and electrostatic-based filtration, but that leakage due to improper fit can degrade performance.[10] A review of available research published in January 2021 concludes that cloth masks are not considered adequate to protect healthcare practitioners in a clinical setting. Another study had volunteers wear masks they made themselves, from cotton T-shirts and following the pattern of a standard tie behind the head surgical mask, and found the number of microscopic particles that leaked to the inside of the homemade masks were twice that of commercial masks. Wearing homemade masks also leaked a median average of three times as many microorganisms as commercial masks. But another study found that masks made of at least two layers T-shirt fabric could be as protective against virus droplets as medical masks, and as breathable. A woman sews a multi-layered woven cloth face mask on a sewing machine. Many people made cloth face masks at home during the pandemic. World Health Organization infographic on how to wear a non-medical fabric mask safely. A peer-reviewed summary of published literature on the filtration properties of cloth and cloth masks suggested two to four layers of plain-weave cotton or flannel, of at least 100 threads per inch. There is a necessary trade-off: increasing the number of layers increases the filtration of the material but decreases breathability. Decreased breathability makes it harder to wear a mask and also increases the amount of leak around the edge of the mask. A plain-language summary of this work,[16] along with a hand-sewn design, suggestions on materials and layering, and how to put on, take off, and clean cloth masks are available. As of May 2020, there was no research on decontaminating and reusing cloth masks. The CDC recommends removing a mask by handling only the ear loops or ties, placing it directly in a washing machine, and immediately washing hands in soap and water for at least twenty seconds. Cold water is considered as effective as warm water for decontamination. The CDC also recommends washing hands before putting on the mask, and again immediately after touching it. There is no information on reusing an interlayer filter. Disposing of filters after a single use may be desirable. A narrative review of the literature on filtration properties of cloth and other household materials did not find support for the idea of using a filter. A layer of cloth, if tolerated, was suggested instead, or a PM2.5 filter, as a third layer. A surgical mask is a loose-fitting, disposable mask that creates a physical barrier separating the mouth and nose of the wearer from potential contaminants in the immediate environment. If worn properly, a surgical mask is meant to help block large-particle droplets, splashes, sprays, or splatter that may contain viruses and bacteria, keeping them from reaching the wearer's mouth and nose. Surgical masks may also help reduce exposure of others to the wearer's saliva and respiratory secretions. Certified medical masks are made of non-woven material and they are mostly multi-layer. Filters may be made of microfibers with an electrostatic charge; that is, the fibers are electrets. An electret filter increases the chances that smaller particles will veer and hit a fiber, rather than going straight through (electrostatic capture). While there is some development work on making electret filtering materials that can be washed and reused, current commercially produced electret filters are ruined by many forms of disinfection, including washing with soap and water or alcohol, which destroys the electric charge.[30] During the COVID-19 pandemic, public health authorities issued guidelines on how to save, disinfect and reuse electret-filter masks without damaging the filtration efficiency. Standard disposable surgical masks are not designed to be washed. Surgical masks may be labeled as surgical, isolation, dental, or medical procedure masks. The material surgical masks are made from is much poorer at filtering very small particles (in range a tenth of a micrometre to a micrometre across) than that of filtering respirators (for example N95, FFP2) and the fit is much poorer. Surgical masks are made of a non-woven fabric created using a melt blowing process. Random control studies of respiratory infections like influenza find little difference in protection between surgical masks and respirators (such as N95 or FFP masks). However, the filtering performance of correctly worn N95/FFP2 type filtering respirators is clearly superior to surgical and to cloth masks and for influenza, work by the UK Health and Safety executive found that live virus penetrated all surgical masks tested but properly fitted respirators reduced the viral dose by a factor of at least a hundred. Tsai Ing-wen, President of Taiwan, wearing a surgical mask Surgical masks made to different standards in different parts of the world have different ranges of particles which they filter. For example, the People's Republic of China regulates two types of such masks: single-use medical masks (Chinese standard YY/T 0969) and surgical masks (YY 0469). The latter ones are required to filter bacteria-sized particles (BFE ≥ 95%) and some virus-sized particles (PFE ≥ 30%), while the former ones are required to only filter bacteria-sized particles. The effectiveness of surgical masks in limiting particle transmission is a function of material and fit. Since the start of the pandemic, scientists have evaluated various modifications to ear loop surgical masks aimed at improving mask efficacy by reducing or eliminating gaps between the mask and face. The CDC evaluated and recommends two such modifications to ear loop masks to reduce transmission of SARS-CoV-2. Under normal use, the CDC found that a surgical mask worn by a coughing individual blocked 41.3% of simulated cough aerosols (0.1–7.0 μm particle size) from reaching a second individual six feet away. However, by applying a knot and tuck technique,[a] 62.9% of particles were blocked. When the surgical mask was covered with a larger cloth mask, 82% of particles were blocked. When both the source and recipient wore masks, 84% of particles were blocked. The number increased to more than 95% when both parties either wore double masks (surgical mask with larger cloth mask) or used the knot and tuck technique. Il Another type of modifications was aimed to improve the comfort of the wearers. Early on in the pandemic, healthcare workers were required to continue wearing surgical masks for 12 or more hours a day. This caused the ear loops of the masks to chafe the back of their ears. Ear savers, plastic straps and hooks that go around wearer's heads, were invented to move the ear loops away from the wearer's ears. They could be made on demand by using 3D printing process. An N95 mask is a particulate-filtering facepiece respirator that meets the N95 air filtration rating of the US National Institute for Occupational Safety and Health, meaning it filters at least 95 percent of airborne particles, while not resistant to oil like the P95. It is the most common particulate-filtering facepiece respirator. It is an example of a mechanical filter respirator, which provides protection against particulates, but not gases or vapors. Like the middle layer of surgical masks, the N95 mask is made of four layers[ of melt-blown nonwoven polypropylene fabric. The corresponding face mask used in the European Union is the FFP2 respirator. Hard electret-filter masks like N95 and FFP masks must fit the face to provide full protection. Untrained users often get a reasonable fit, but fewer than one in four gets a perfect fit. Fit testing is thus standard. A line of petroleum jelly on the edge of the mask. has been shown to reduce edge leakage in lab tests using mannequins that simulate breathing. Some N95 series respirators, especially those intended for industrial use, have an exhalation valve to improve comfort, making exhalation easier and reducing leakage on exhalation and steaming-up of glasses. But those respirators are not reliable for the control of infected people (source control) in respiratory diseases such as COVID-19, because infected users (asymptomatic or not) would transmit the virus to others through the valve. During the COVID-19 pandemic, there were shortages of filtering facepiece respirators, and they had to be used for extended periods, and/or disinfected and reused. At the time, public health authorities issued guidelines on how to save, disinfect and reuse masks, as some disinfection methods damaged their filtration efficiency. Some hospitals stockpiled used masks as a precaution, and some had to sanitize and reuse masks. The US Centers for Disease Control and Prevention (CDC) does not recommend the use of face shields as a substitute for masks to help slow the spread of COVID-19.[54] In a study by Lindsley et al. (7 January 2021) funded by the National Institute for Occupational Safety and Health, part of the CDC, face shields were found to block very few cough aerosols in contrast to face coverings – such as cloth masks, procedure masks, and N95 respirators – indicating that face shields are not effective as source control devices for small respiratory aerosols and that face coverings are more effective than face shields as source control devices to reduce the community transmission of SARS-CoV-2. In a scoping review, Godoy et al. (5 May 2020) said face shields are used for barrier protection against splash and splatter contamination, but should not be used as primary protection against respiratory disease transmission due to the lack of a peripheral seal rather than as an adjunct to other facial protection. They remarked that face shields have been used like this alongside medical-grade masks during the COVID-19 pandemic. They cited a cough simulation study by Lindsley et al. (2014) in which face shields were shown to reduce the risk of inhalation exposure up to 95% immediately following aerosol production, but the protection was decreased with smaller aerosol particles and persistent airborne particles around the sides. A systematic review of observational studies on the transmission of coronaviruses, funded by the World Health Organization found that eye protection including face shields was associated with less infection (adjusted odds ratio 0.22; 95% confidence interval 0·12 to 0·39), but the evidence was rated as low certainty. Elastomeric respirators are reusable personal protective equipment comprising a tight-fitting half-facepiece or full-facepiece respirator with exchangeable filters such as cartridge filters. They provide an alternative respiratory protection option to filtering facepiece respirators such as N95 masks for healthcare workers during times of short supply caused by the pandemic, as they can be reused over an extended period in healthcare settings. However, elastomeric respirators have a vent to exhalate the air outwards and unfiltered, so the wearer must be attentive that he or she is not infected with SARS-CoV-2, to prevent a possible transmission of the virus to others through the vent. For the COVID-19 response when supplies are short, the US CDC says contingency and crisis strategies should be followed: Each elastomeric respirator is issued for the exclusive use of an individual healthcare provider, but must be cleaned and disinfected as often as necessary to remain unsoiled and sanitary. If there is no other option than to share a respirator between healthcare providers, the respirator must be cleaned and disinfected before it is worn by a different individual. Filters (except for unprotected disc types) may be used for an extended period, but the filter housing of cartridge types must be disinfected after each patient interaction. A powered air-purifying respirator (PAPR) is a personal protective equipment in which a device with a filter and fan creates a highly filtered airflow towards the headpiece and a positive outflow of air from the headpiece. There is an increased risk for healthcare workers to become exposed to SARS-CoV-2 when they conduct aerosol-generating procedures on COVID-19 patients, which is why it is argued that such situations may require enhanced personal protective equipment (i.e., higher than N95) such as PAPRs for healthcare workers. In a systematic review, Licina, Silvers, and Stuart (8 August 2020) said field studies indicate that there was equivalent rates of infection between healthcare workers, who performed airway procedures on critical COVID-19 patients, utilizing PAPRs or other appropriate respiratory equipment (such as N95 or FFP2), but remarked that there is a need to further collect field data about optimal respiratory protection during highly virulent pandemics. Some masks include an exhalation valve to expel the breath outwards, but that current of air is not filtered. Certification (as N95 or FFP2) is about the mask itself and does not warrant any safety about the air that is exhaled. Putting tape over the exhalation valve can make a mask or respirator as effective as one without a valve. Scientists have visualized droplet dispersal for masks with exhalation valves and face shields, and concluded that they can be ineffective against COVID-19 spread (e.g., after a cough) and recommended alternatives. The use of face masks or coverings by the general public has been recommended by health officials to minimize the risk of transmissions, with authorities either requiring their use in certain settings, such as on public transport and in shops, or universally in public. Health officials have advised that medical-grade face masks, such as respirators, should be prioritized for use by healthcare workers in view of critical shortages, so they generally first and foremost recommend cloth masks for the general public. The recommendations have changed as the body of scientific knowledge evolved. According to #Masks4All, about 95% of the world population lives in countries where the government and leading disease experts recommend or require the use of masks in public places to limit the spread of COVID-19. Early in 2020, the WHO had only recommended medical masks for people with suspected infection and respiratory symptoms, their caregivers and those sharing living space, and healthcare workers.[71][72][73] In April 2020, the WHO acknowledged that wearing a medical mask can limit the spread of certain respiratory viral diseases including COVID-19, but claimed that medical masks would create a false sense of security and neglect of other necessary measures, such as hand hygiene. The early WHO advice on limited mask usage was scrutinized for several reasons. First, experts and researchers pointed out the asymptomatic transmission of the virus. Second, according to Marteau et al. (27 July 2020), available evidence does not support the notion that masking adversely affects hand hygiene: Dame Theresa Marteau, one of the researchers, remarked that "The concept of risk compensation, rather than risk compensation itself, seems the greater threat to public health through delaying potentially effective interventions that can help prevent the spread of disease." The WHO revised its mask guidance in June 2020, with its officials acknowledging that studies indicated asymptomatic or pre-symptomatic spread.[81] The updated advice recommended that the general public should wear non-medical fabric masks where there is known or suspected widespread transmission and where physical distancing is not possible, and that vulnerable people (60 and over, or with underlying health risks) and people with any symptoms suggestive of COVID-19 as well as caregivers and healthcare workers should wear surgical or procedure masks.[68] They stated that the purpose of mask usage is to prevent the wearer transmitting the virus to others (source control) and to offer protection to healthy wearers against infection (prevention). The WHO advises that non-medical fabric masks should comprise a minimum of three layers, suggesting an inner layer made of absorbent material (such as cotton), a middle layer made of non-woven material (such as polypropylene) which may enhance filtration or retain droplets, and an outer layer made of non-absorbent material (such as polyester or its blends) which may limit external contamination from penetration. On 21 August 2020, the WHO and UNICEF released an annex guidance for children.[83] For children five and younger, they advise that masks should not be required in consideration to a child's developmental milestones, compliance challenges, and autonomy required to use a mask properly, but recognized that the evidence supporting their cut-off age is limited and countries may hold a different and lower age of cut-off. For children 6–11, they advise that mask usage should be decided in consideration of several factors including the intensity of local viral transmission, (the latest evidence about) the risk of infection for the age group, the social and cultural environment (which influences social interactions in communities and populations), the capacity to comply with appropriate mask usage, the availability of appropriate adult supervision, and the potential impact on learning and psychosocial development, as well as additional factors involving specific settings or circumstances (such as disabilities, underlying diseases, elderly people, sport activities, and schools). For children 12 and older, they advise that masks should be worn under the same conditions for adults in accordance to WHO guidance or national guidelines. Regarding the use of non-medical fabric masks in the general population, the WHO has stated that high-quality evidence for its widespread use is limited, but advises governments to encourage its use as physical distancing may not be possible in some settings, there is some evidence for asymptomatic transmission, and masks could be helpful to provide a barrier to limit the spread of potentially infectious droplets.

 

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