Summaries of Mask Studies
Health Freedom Ohio Research Team
Introduction: Here we provide an extensive summary of peer-reviewed literature as well as quotes from medical professionals on the effectiveness of face masks against viruses, as well as potential health concerns that could arise from improper face mask use. It is important to note that few of these studies look at SARS-CoV-2, for the simple reason that little research has been done on what is a presumably new virus. We also note where studies are flawed by making our own comments in [brackets].
Scientific literature examining the effectiveness of face masks of various types against SARS-CoV-2 and other viruses:
A cluster randomised trial of cloth masks compared with medical masks in healthcare workers
Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Cloth masks should not be recommended for health care workers, particularly in high-risk settings such as emergency, infectious disease, respiratory disease and intensive care wards.
N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial
In this pragmatic, cluster randomized trial that involved multiple outpatient sites at 7 health care delivery systems across a wide geographic area over 4 seasons of peak viral respiratory illness, there was no significant difference between the effectiveness of N95 respirators and medical masks in preventing laboratory-confirmed influenza among participants routinely exposed to respiratory illnesses in the workplace. In addition, there were no significant differences between N95 respirators and medical masks in the rates of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness, and influenza like illness among participants (including coronaviruses). A sensitivity analysis suggested that the primary analysis reported was fairly robust to the missing outcome data with quantitative outcomes varying by less than 5%. This supports the finding that neither N95 respirators nor medical masks were more effective in preventing laboratory-confirmed influenza or other viral respiratory infection or illness among participants when worn in a fashion consistent with current US clinical practice.
Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers From Acute Respiratory Infection: A Systematic Review and Meta-Analysis
A meta-analysis of several published studies to look at comparing N95 respirators and surgical masks for the prevention of transmissible acute respiratory infections in a hospital setting and also surrogate exposure studies to detect leakage and penetration from the masks were done. Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, the meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings. The clinical significance was further put into question by the wide 95% CI of the data used in the meta-analysis. The potential harm or negative effects of using respirators and masks were also excluded from the study. The surrogate studies showed that the N95 masks were superior to surgical masks when it came to droplet penetration and leakage but the effects were not statistically significant to prevent infection.
Simple Respiratory Protection--Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 Nm Size Particles
Testing filtration performance against virus nano sized particles using various cloth materials were tested against N95 masks. After using two different face velocities, the results showed a range of 40-90% instantaneous penetration in all fabrics tested. Aerosol particles were much higher than the penetration for N95 respirator filter. Conclusions of results indicate fabric masks of any type provide marginal protection including virus particles.
Respiratory virus shedding in exhaled breath and efficacy of face masks
Surgical masks reduce detection of influenza RNA in respiratory droplets and coronavirus RNA in aerosols from individuals that were diagnosed with those infections. Viral RNA was detected in respiratory droplets from individuals both wearing and not wearing a mask: 30% of coronavirus patients wearing a mask vs 40% of those not wearing a mask, which was not statistically significant. The authors concluded that aerosol transmission is a potential mode of transmission for coronavirus, and that masks could be used by ill people to reduce onward transmission.
Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks
Authors observe that the pore sizes of cloth masks are substantially larger than the particular matter they are intended to filter. Filtering efficiency was noted to range between 63% and 84% with a 20% decrease in filtering efficiency after the 4th washing and drying cycle.
Surgical mask filter and fit performance.
Masks have been used since the early 1900’s to help reduce bacteria spread. The goal of this study was to evaluate the filter performance since the shift has been to use masks as respiratory protection devices. Filter penetration was measured for at least 3 replicates of 9 surgical masks using monodisperse latex sphere aerosols and facial fit was measured on 20 subjects for the 5 masks. The study concluded that none of these surgical masks exhibited adequate filter performance and facial fit characteristics to be considered respiratory protection devices.
The Use of Masks and Respirators to Prevent Transmission of Influenza: A Systematic Review of the Scientific Evidence
Of 17 eligible studies, mask use appeared to reduce transmission of some viruses in some cases, however study authors note that findings were not conclusive and may not be applicable to all viruses, such as influenza, and that many of the studies were of suboptimal quality. Personal hygiene (washing hands) and correct and consistent usage (uncommon outside medical professionals in medical settings) are most likely the main factors in reducing viral transmission.
Evaluating the Efficacy of Cloth Facemasks in Reducing Particulate Matter Exposure
”Standard N95 mask performance was used as a control to compare the results with cloth masks, and our results suggest that cloth masks are only marginally beneficial in protecting individuals from particles<2.5 μm. Compared with cloth masks, disposable surgical masks are more effective in reducing particulate exposure.”
Viruses are 0.004 to 0.1 μm in size or about 100 times smaller than bacteria.
Identifying airborne transmission as the dominant route for the spread of COVID-19
This study examined the impact of different mitigation strategies (social distancing, mask wearing, etc) implemented in different world governments on changes in epidemic curves. The analysis was based on linear interpolation on the observed epidemic curves. This article makes strong claims about airborne transmission and significant impact of the aforementioned mitigation strategies; in other words, the claim that “masks work”. However, this analysis is biased by an ecological fallacy, that observations made at the population level are appropriate at the individual-level, and disregards any impact of changing treatment modalities, differences in susceptibility by age, and differences over time in other important public health parameters including recovery rate, hospitalization rate, and death rate, all of which declined in many principalities independent of mitigation strategy.
Universal Masking is Urgent in the COVID-19 Pandemic: SEIR and Agent Based Models, Empirical Validation, Policy Recommendations
This paper develops an SEIR (susceptible-exposed-infectious-recovered) theoretical transmission model to better understand the impact of wearing masks. As with many theoretical models, the parameter estimates were based on hypothesized values not rooted in actual data. A few papers were cited that said masks were effective, but the authors did not describe how these few reports led to their parameter estimates. A “validation study” compared the “degree of success in managing COVID-19” by countries and provinces with different “masking cultures”; [such an analysis is prone to ecological fallacy and confounding]. While this paper makes strong recommendations for universal masking, it is based on strong underlying assumptions.
Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks (Update June 15, 2020)
This presents an ecological analysis, examining the association between country-level coronavirus mortality and several population-level factors. In multivariable analyses, lockdowns and per-capita mask wearing were associated with lower mortality, though importantly, neither were statistically significant.
Assessment of influenza virus exposure and recovery from contaminated surgical masks and N95 respirators
These results also support previous studies that suggest that virus trapped on the outside of
facemasks and respirators may pose an indirect contact transmission risk as the healthcare
worker doffs these PPE after seeing a patient or continues to wear their PPE for an extended
period of time.
Contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers
Virus positivity was significantly higher in masks samples worn for > 6 h. Respiratory pathogens
on the outer surface of the used medical masks may result in self-contamination. The risk is
higher with longer duration of mask use (> 6 h). Most of the participants (83.8%, 124/148) reported at least one problem associated with mask use. Commonly reported problems were pressure on face (16.9%, 25/148), breathing difficulty (12.2%, 18/148), discomfort (9.5% 14/148), trouble communicating with the patient (7.4%, 11/148) and headache (6.1%, 9/148).
Surgical masks as source of bacterial contamination during operative procedures
This study provides strong evidence for the identification that surgical masks as source of bacterial contamination during operative procedures, which should be a cause for alarm and attention in the prevention of surgical site infection in clinical practice. The bacterial count on the surface of SMs increased with extended operating times; significant difference was found between the 4- to 6-hour and 0-hour groups. These results demonstrated that the contamination of the SM surface worsens with wearing time extension. We recommend that surgeons should change the mask after each operation, especially those beyond 2 hours.
Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China
The new study was a retrospective cohort study of 124 households with an index SARSCoV-2 case and 355 uninfected household contacts. Households in which masks were used by at least one family member (including the index case) prior to the development of symptoms by the index case were associated with decreased risk of incident infections, after adjusting for other hygiene and infection control practices, physical distance to index case, environmental factors, and presence of diarrhea in the index case (adjusted odds ratio 0.21, 95% confidence interval 0.06 to 0.79). There was no association between mask use after illness onset in the index case and risk of SARS-CoV-2 infections in family members. Masks included N95 respirators, surgical masks, or cloth face coverings, and the study did not conduct analyses by specific mask type. The study was susceptible to recall bias; in addition, the analysis used households (rather than exposed individuals) as the unit of analysis and did not analyze mask use by the index case (“source control”) separately from mask use by household contacts. The applicability of findings to wearing of masks in public is also uncertain. Therefore, the strength of evidence on masks in community settings for prevention of SARS-CoV-2 infection is insufficient.
*** Summary provided by https://effectivehealthcare.ahrq.gov/sites/default/files/pdf/masks-prevention-covid-surveillance-report.pdf?fbclid=IwAR2Dnd1Lqb2tpB-NJR0A-Ae_SXYeZ2tacqrugyunNAke1ce4hn8FbQgVvUM
Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis
Meta-analysis of randomized controlled trials indicated a protective effect of masks and respirators against self-reported clinical respiratory illness (CRI) and influenza-like illness (ILI) in healthcare workers, and the protective effect against laboratory-confirmed viral infections was not statistically significant. N95 respirators conferred superior protection compared to standard face masks against CRI and laboratory-confirmed bacterial, but not viral infections or ILI. Meta-analysis of observational studies provided evidence of a protective effect of masks and N95 respirators against severe acute respiratory syndrome (SARS). The existing evidence is sparse and findings are inconsistent within and across studies, and the studies included in this analysis may have been prone to recall bias.
Commentaries not using data:
Should I Wear a Face Mask?
While this is not in a scientific journal, it is written by an environmental, health and safety manager, responsible for respiratory protection. The writer has degrees in engineering/materials science, and pharmacology and toxicology.
First, cloth face masks show only marginal filtration performance against virus-size particles when sealed around the edge. Face seal leakage will further decrease the respiratory protection offered by fabric materials. Thus, cloth masks are not recommended. Second, surgical masks also do not form a seal, which allows for air leakage and thus respiratory droplets. Third, N95 do not provide complete protection against small virions. In addition, training is required for effective PPE use. Frequently touching ones face to adjust an ill-fitting or uncomfortable mask increases the risk of viral exposure. In summary, the general public should not be wearing face mask to lessen viral transmission because of the potential drawbacks.
COMMENTARY: Masks-for-all for COVID-19 not based on sound data
Masks may give people a false sense of security. The general public who do not have symptoms of COVID-19-like illness should not routinely wear cloth or surgical face masks. There is no scientific evidence that face masks are effective in reducing the risk of SARS-CoV-2 transmission. Cloth masks exhibit very low filter efficiency. Even masks that fit well against the face will not prevent inhalation of small particles by the wearer or emission of small particles from the wearer. Cloth masks offer no protection for healthcare workers inhaling infectious particles near an infected or confirmed patient.
Universal Masking in Hospitals in the Covid-19 Era
Universal masking of the public offers little, if any protection and is mostly a knee jerk reaction to fear and anxiety over the virus. Universal masking of hospital personnel offers very little protection and must be used in conjunction with other meticulous measures as outlined below. It could actually lead to more infections if the other measures are not followed since people wearing masks have a tendency to touch their face more often.
Quoting directly from the New England Journal of Medicine:
"We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic."
In hospital settings where Covid-19 infections are present, the article states, “A mask alone in this setting will reduce risk only slightly, however, since it does not provide protection from droplets that may enter the eyes or from fomites on the patient or in the environment that providers may pick up on their hands and carry to their mucous membranes (particularly given the concern that mask wearers may have an increased tendency to touch their faces)….What is clear, however, is that universal masking alone is not a panacea. A mask will not protect providers caring for a patient with active Covid-19 if it’s not accompanied by meticulous hand hygiene, eye protection, gloves, and a gown. A mask alone will not prevent health care workers with early Covid-19 from contaminating their hands and spreading the virus to patients and colleagues. Focusing on universal masking alone may, paradoxically, lead to more transmission of Covid-19 if it diverts attention from implementing more fundamental infection-control measures.”
Universal Masking in the Covid-19 Era
This letter was a response to the letter cited above. It is interesting that in the original article, the authors state that is “unclear to what extent transmission from asymptomatic individuals contributed to the spread of infection”, but in this article, they say that asymptomatic or presymptomatic individuals may be “highly contagious”. Here, the authors emphasize the importance of masks for passing encounters in public spaces, then say that the risk of SARS-CoV-2 transmission is strongly correlated with intensity and duration of contact [though “passing encounters” are not intense or of long duration]. The authors close by saying they “support the calls of public health agencies for all people to wear masks when circumstances compel them to be within 6 ft of others for sustained periods.”
Comprehensive Review of Mask Utility and Challenges During the COVID-19 Pandemic
The paper discusses the universal masking strategy and challenges faced during COVID-19. Symptomatic patients who wore cloth or surgical masks were seen to not filter out SARS-COV2 during coughing. In one study more contamination was found outside the mask than on the inside owing to the masks’ aerodynamic properties. Universal masking may also give a false impression of protection and may result in increased face touching leading to more contamination.
Furthermore, even the most effective mask is useless if not worn correctly or fitted properly. Though healthcare workers may feel falsely safe or protected while wearing a mask (particularly loose-fitting industrial masks), minimal air leakage, regular fit-testing and seal checks with N95 respirators are of paramount importance. The authors conclude that masking alone is not sufficient to stop the spread of COVID-19 and other non-pharmacological interventions such as social distancing, quarantining/isolation, and diligent hand hygiene must be coupled with mask wearing for better outcomes.
A possible solution to alleviate mask shortages that might arise due to universal mask wearing is to modify the mask policy to stagger the requirement based on the severity of community transmission in each particular area of residence.
Rational use of face masks in the COVID-19 pandemic
(The following are direct quotes from the paper.)
“Evidence that face masks can provide effective protection against respiratory infections in the community is scarce, as acknowledged in recommendations from the UK and Germany…. It would be reasonable to suggest vulnerable individuals avoid crowded areas and use surgical face masks rationally when exposed to high-risk areas. As evidence suggests COVID-19 could be transmitted before symptom onset, community transmission might be reduced if everyone, including people who have been infected but are asymptomatic and contagious, wear face masks…. One advantage of universal use of face masks is that it prevents discrimination of individuals who wear masks when unwell because everybody is wearing a mask…. WHO currently recommends that people should wear face masks if they have respiratory symptoms or if they are caring for somebody with symptoms. Perhaps it would also be rational to recommend that people in quarantine wear face masks if they need to leave home for any reason, to prevent potential asymptomatic or presymptomatic transmission. In addition, vulnerable populations, such as older adults and those with underlying medical conditions, should wear face masks if available. Universal use of face masks could be considered if supplies permit.”
Health concerns associated with wearing face masks:
Preliminary Report on Surgical Mask Induced Deoxygenation During Major Surgery
“Our study revealed a decrease in the oxygen saturation of arterial pulsations (SpO2) and a slight increase in pulse rates compared to preoperative values in all surgeon groups. The decrease was more prominent in the surgeons aged over 35.”
“Oxygen saturation of hemoglobin decreased significantly after the operations in both age groups (p<0.0001). The post operational decrease was more prominent in surgeons over 35 when compared to the surgeons under 35 (p=0.0073)”
The Physiological Impact of Wearing an N95 Mask During Hemodialysis as a Precaution Against SARS in Patients With End-Stage Renal Disease
Seventy percent of the patients showed a reduction in partial pressure of oxygen (PaO2), and 19% developed various degrees of hypoxemia. Wearing an N95 mask significantly reduced the PaO2 level (101.7 +/- 12.6 to 92.7 +/- 15.8 mm Hg, p = 0.006), increased the respiratory rate (16.8 +/- 2.8 to 18.8 +/- 2.7/min, p < 0.001), and increased the occurrence of chest discomfort (3 to 11 patients, p = 0.014) and respiratory distress (1 to 17 patients, p < 0.001).”
Headaches Associated With Personal Protective Equipment - A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19
Healthcare workers assigned to high risk Covid hospital areas in Singapore were mandated to wear personal protective equipment, so a questionnaire was given to them to determine if increased in headaches were occurring in 158 participants. The study indicates this population wore a mask and goggles greater than 4 hours per day. Out of 158 respondents, 128 (81.0%) respondents developed de novo PPE-associated headaches.
Carbon Dioxide Rebreathing in Respiratory Protective Devices: Influence of Speech and Work Rate in Full-Face Masks
Overall, the results of the study indicate speech and low work rates significantly increase CO2 rebreathing in RPDs. Based on Australian respirator design standards it is evident speech could contribute to inspired CO2 exceeding the maximal allowable concentrations in inspired air…The implication of these findings is that high CO2 concentrations in full face RPDs may be linked to wearer discomfort and contribute to reduced tolerability and wear time of the device. Since many occupations require workers to communicate while wearing RPDs these findings must be taken into consideration.
The Physiological Impact of N95 Masks on Medical Staff
Authors of this clinical trial observe that, "Wearing N95 masks results in hypooxygenemia [lowered blood oxygen levels] and hypercapnia [increased blood carbon dioxide levels] which reduce working efficiency and the ability to make correct decision[s]... dizziness, headache, and short[ness] of breath are commonly experienced by the medical staff wearing N95 masks."
Media reports including interviews with physicians and scientists:
Gregory Poland, MD, an infectious disease & vaccine expert at the Mayo Clinic, stated that the
mask is an indicator of a constellation of behaviors that collectively reduce transmission.
Wearing a mask leads someone to touch their face less often & serves as a constant
psychological reminder to do other known infection prevention behaviors, such as frequent,
rigorous hand-washing and keeping a good distance from other people.
America’s surgeon general, Jerome Adams, M.D., M.P.H., said in an interview in March that masks can be dangerous is because people tend to touch their masks many times per hour and can spread the disease that way. [The media has reported that Dr. Adams has backtracked on this statement.]
Dr. Jennie Harries says that masks could actually “trap the virus” and cause the person wearing it to breathe it in. “For the average member of the public walking down a street, it is not a good idea” to wear a face mask in the hope of preventing infection. “Because of these behavioural issues, people can adversely put themselves at more risk than less.”
Dr. Jake Dunning said “Face masks must be worn correctly, changed frequently, removed properly, disposed of safely and used in combination with good universal hygiene behaviour in order for them to be effective.”
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