Facemasks in the COVID-19 era: A
health hypothesis
Autor: Baruch Vainshelboim
Estudio revisado por pares y publicado en NCBI (National Center for Biotechnological
Information).
El Centro Nacional de Información Biotecnológica (NCBI) forma parte de la Biblioteca Nacional de
Medicina de Estados Unidos, una división de los Institutos Nacionales de Salud. Está aprobado y
financiado por el gobierno de los Estados Unidos.

Abstract
Many countries across the globe utilized medical and non-medical facemasks as nonpharmaceutical intervention for reducing the transmission and infectivity of coronavirus disease2019 (COVID-19). Although, scientific evidence supporting facemasks’ efficacy is lacking,
adverse physiological, psychological and health effects are established. Is has been
hypothesized that facemasks have compromised safety and efficacy profile and should be
avoided from use. The current article comprehensively summarizes scientific evidences with
respect to wearing facemasks in the COVID-19 era, providing prosper information for public
health and decisions making.

Introduction
Facemasks are part of non-pharmaceutical interventions providing some breathing barrier to the
mouth and nose that have been utilized for reducing the transmission of respiratory pathogens
[1]. Facemasks can be medical and non-medical, where two types of the medical masks
primarily used by healthcare workers [1], [2]. The first type is National Institute for Occupational
Safety and Health (NIOSH)-certified N95 mask, a filtering face-piece respirator, and the second
type is a surgical mask [1]. The designed and intended uses of N95 and surgical masks are
different in the type of protection they potentially provide. The N95s are typically composed of
electret filter media and seal tightly to the face of the wearer, whereas surgical masks are
generally loose fitting and may or may not contain electret-filtering media. The N95s are
designed to reduce the wearer’s inhalation exposure to infectious and harmful particles from the
environment such as during extermination of insects. In contrast, surgical masks are designed
to provide a barrier protection against splash, spittle and other body fluids to spray from the
wearer (such as surgeon) to the sterile environment (patient during operation) for reducing the
risk of contamination [1].
The third type of facemasks are the non-medical cloth or fabric masks. The non-medical
facemasks are made from a variety of woven and non-woven materials such as Polypropylene,
Cotton, Polyester, Cellulose, Gauze and Silk. Although non-medical cloth or fabric facemasks
are neither a medical device nor personal protective equipment, some standards have been
developed by the French Standardization Association (AFNOR Group) to define a minimum
performance for filtration and breathability capacity [2]. The current article reviews the scientific
evidences with respect to safety and efficacy of wearing facemasks, describing the
physiological and psychological effects and the potential long-term consequences on health.

Hypothesis
On January 30, 2020, the World Health Organization (WHO) announced a global public health
emergency of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) causing illness
of coronavirus disease-2019 (COVID-19) [3]. As of October 1, 2020, worldwide 34,166,633
cases were reported and 1,018,876 have died with virus diagnosis. Interestingly, 99% of the
detected cases with SARS-CoV-2 are asymptomatic or have mild condition, which contradicts

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with the virus name (severe acute respiratory syndrome-coronavirus-2) [4]. Although infection
fatality rate (number of death cases divided by number of reported cases) initially seems quite
high 0.029 (2.9%) [4], this overestimation related to limited number of COVID-19 tests
performed which biases towards higher rates. Given the fact that asymptomatic or minimally
symptomatic cases is several times higher than the number of reported cases, the case fatality
rate is considerably less than 1% [5]. This was confirmed by the head of National Institute of
Allergy and Infectious Diseases from US stating, “the overall clinical consequences of COVID19 are similar to those of severe seasonal influenza” [5], having a case fatality rate of
approximately 0.1% [5], [6], [7], [8]. In addition, data from hospitalized patients with COVID-19
and general public indicate that the majority of deaths were among older and chronically ill
individuals, supporting the possibility that the virus may exacerbates existing conditions but
rarely causes death by itself [9], [10]. SARS-CoV-2 primarily affects respiratory system and can
cause complications such as acute respiratory distress syndrome (ARDS), respiratory failure
and death [3], [9]. It is not clear however, what the scientific and clinical basis for wearing
facemasks as protective strategy, given the fact that facemasks restrict breathing, causing
hypoxemia and hypercapnia and increase the risk for respiratory complications, selfcontamination and exacerbation of existing chronic conditions [2], [11], [12], [13], [14].
Of note, hyperoxia or oxygen supplementation (breathing air with high partial O2 pressures that
above the sea levels) has been well established as therapeutic and curative practice for variety
acute and chronic conditions including respiratory complications [11], [15]. It fact, the current
standard of care practice for treating hospitalized patients with COVID-19 is breathing 100%
oxygen [16], [17], [18]. Although several countries mandated wearing facemask in health care
settings and public areas, scientific evidences are lacking supporting their efficacy for reducing
morbidity or mortality associated with infectious or viral diseases [2], [14], [19]. Therefore, it has
been hypothesized: 1) the practice of wearing facemasks has compromised safety and efficacy
profile, 2) Both medical and non-medical facemasks are ineffective to reduce human-to-human
transmission and infectivity of SARS-CoV-2 and COVID-19, 3) Wearing facemasks has adverse
physiological and psychological effects, 4) Long-term consequences of wearing facemasks on
health are detrimental.

Evolution of hypothesis
Breathing Physiology
Breathing is one of the most important physiological functions to sustain life and health. Human
body requires a continuous and adequate oxygen (O2) supply to all organs and cells for normal
function and survival. Breathing is also an essential process for removing metabolic byproducts
[carbon dioxide (CO2)] occurring during cell respiration [12], [13]. It is well established that
acute significant deficit in O2 (hypoxemia) and increased levels of CO2 (hypercapnia) even for
few minutes can be severely harmful and lethal, while chronic hypoxemia and hypercapnia
cause health deterioration, exacerbation of existing conditions, morbidity and ultimately mortality
[11], [20], [21], [22]. Emergency medicine demonstrates that 5–6 min of severe hypoxemia
during cardiac arrest will cause brain death with extremely poor survival rates [20], [21], [22],
[23]. On the other hand, chronic mild or moderate hypoxemia and hypercapnia such as from
wearing facemasks resulting in shifting to higher contribution of anaerobic energy metabolism,
decrease in pH levels and increase in cells and blood acidity, toxicity, oxidative stress, chronic
inflammation, immunosuppression and health deterioration [24], [11], [12], [13].

Efficacy of facemasks
The physical properties of medical and non-medical facemasks suggest that facemasks are
ineffective to block viral particles due to their difference in scales [16], [17], [25]. According to
the current knowledge, the virus SARS-CoV-2 has a diameter of 60 nm to 140 nm [nanometers
(billionth of a meter)] [16], [17], while medical and non-medical facemasks’ thread diameter
ranges from 55 µm to 440 µm [micrometers (one millionth of a meter), which is more than 1000
times larger [25]. Due to the difference in sizes between SARS-CoV-2 diameter and facemasks
thread diameter (the virus is 1000 times smaller), SARS-CoV-2 can easily pass through any

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facemask [25]. In addition, the efficiency filtration rate of facemasks is poor, ranging from 0.7%
in non-surgical, cotton-gauze woven mask to 26% in cotton sweeter material [2]. With respect to
surgical and N95 medical facemasks, the efficiency filtration rate falls to 15% and 58%,
respectively when even small gap between the mask and the face exists [25].
Clinical scientific evidence challenges further the efficacy of facemasks to block human-tohuman transmission or infectivity. A randomized controlled trial (RCT) of 246 participants [123
(50%) symptomatic)] who were allocated to either wearing or not wearing surgical facemask,
assessing viruses transmission including coronavirus [26]. The results of this study showed that
among symptomatic individuals (those with fever, cough, sore throat, runny nose ect…) there
was no difference between wearing and not wearing facemask for coronavirus droplets
transmission of particles of >5 µm. Among asymptomatic individuals, there was no droplets or
aerosols coronavirus detected from any participant with or without the mask, suggesting that
asymptomatic individuals do not transmit or infect other people [26]. This was further supported
by a study on infectivity where 445 asymptomatic individuals were exposed to asymptomatic
SARS-CoV-2 carrier (been positive for SARS-CoV-2) using close contact (shared quarantine
space) for a median of 4 to 5 days. The study found that none of the 445 individuals was
infected with SARS-CoV-2 confirmed by real-time reverse transcription polymerase [27].
A meta-analysis among health care workers found that compared to no masks, surgical mask
and N95 respirators were not effective against transmission of viral infections or influenza-like
illness based on six RCTs [28]. Using separate analysis of 23 observational studies, this metaanalysis found no protective effect of medical mask or N95 respirators against SARS virus [28].
A recent systematic review of 39 studies including 33,867 participants in community settings
(self-report illness), found no difference between N95 respirators versus surgical masks and
surgical mask versus no masks in the risk for developing influenza or influenza-like illness,
suggesting their ineffectiveness of blocking viral transmissions in community settings [29].
Another meta-analysis of 44 non-RCT studies (n = 25,697 participants) examining the potential
risk reduction of facemasks against SARS, middle east respiratory syndrome (MERS) and
COVID-19 transmissions [30]. The meta-analysis included four specific studies on COVID-19
transmission (5,929 participants, primarily health-care workers used N95 masks). Although the
overall findings showed reduced risk of virus transmission with facemasks, the analysis had
severe limitations to draw conclusions. One of the four COVID-19 studies had zero infected
cases in both arms, and was excluded from meta-analytic calculation. Other two COVID-19
studies had unadjusted models, and were also excluded from the overall analysis. The metaanalytic results were based on only one COVID-19, one MERS and 8 SARS studies, resulting in
high selection bias of the studies and contamination of the results between different viruses.
Based on four COVID-19 studies, the meta-analysis failed to demonstrate risk reduction of
facemasks for COVID-19 transmission, where the authors reported that the results of metaanalysis have low certainty and are inconclusive [30].
In early publication the WHO stated that “facemasks are not required, as no evidence is
available on its usefulness to protect non-sick persons” [14]. In the same publication, the WHO
declared that “cloth (e.g. cotton or gauze) masks are not recommended under any
circumstance” [14]. Conversely, in later publication the WHO stated that the usage of fabricmade facemasks (Polypropylene, Cotton, Polyester, Cellulose, Gauze and Silk) is a general
community practice for “preventing the infected wearer transmitting the virus to others and/or to
offer protection to the healthy wearer against infection (prevention)” [2]. The same publication
further conflicted itself by stating that due to the lower filtration, breathability and overall
performance of fabric facemasks, the usage of woven fabric mask such as cloth, and/or nonwoven fabrics, should only be considered for infected persons and not for prevention practice in
asymptomatic individuals [2]. The Central for Disease Control and Prevention (CDC) made
similar recommendation, stating that only symptomatic persons should consider wearing
facemask, while for asymptomatic individuals this practice is not recommended [31]. Consistent
with the CDC, clinical scientists from Departments of Infectious Diseases and Microbiology in
Australia counsel against facemasks usage for health-care workers, arguing that there is no
justification for such practice while normal caring relationship between patients and medical
staff could be compromised [32]. Moreover, the WHO repeatedly announced that “at present,

3

there is no direct evidence (from studies on COVID-19) on the effectiveness face masking of
healthy people in the community to prevent infection of respiratory viruses, including COVID19”[2]. Despite these controversies, the potential harms and risks of wearing facemasks were
clearly acknowledged. These including self-contamination due to hand practice or non-replaced
when the mask is wet, soiled or damaged, development of facial skin lesions, irritant dermatitis
or worsening acne and psychological discomfort. Vulnerable populations such as people with
mental health disorders, developmental disabilities, hearing problems, those living in hot and
humid environments, children and patients with respiratory conditions are at significant health
risk for complications and harm [2].

Physiological effects of wearing facemasks
Wearing facemask mechanically restricts breathing by increasing the resistance of air
movement during both inhalation and exhalation process [12], [13]. Although, intermittent
(several times a week) and repetitive (10–15 breaths for 2–4 sets) increase in respiration
resistance may be adaptive for strengthening respiratory muscles [33], [34], prolonged and
continues effect of wearing facemask is maladaptive and could be detrimental for health [11],
[12], [13]. In normal conditions at the sea level, air contains 20.93% O2 and 0.03% CO2,
providing partial pressures of 100 mmHg and 40 mmHg for these gases in the arterial blood,
respectively. These gas concentrations significantly altered when breathing occurs through
facemask. A trapped air remaining between the mouth, nose and the facemask is rebreathed
repeatedly in and out of the body, containing low O2 and high CO2 concentrations, causing
hypoxemia and hypercapnia [35], [36], [11], [12], [13]. Severe hypoxemia may also provoke
cardiopulmonary and neurological complications and is considered an important clinical sign in
cardiopulmonary medicine [37], [38], [39], [40], [41], [42]. Low oxygen content in the arterial
blood can cause myocardial ischemia, serious arrhythmias, right or left ventricular dysfunction,
dizziness, hypotension, syncope and pulmonary hypertension [43]. Chronic low-grade
hypoxemia and hypercapnia as result of using facemask can cause exacerbation of existing
cardiopulmonary, metabolic, vascular and neurological conditions [37], [38], [39], [40], [41], [42].
Table 1 summarizes the physiological, psychological effects of wearing facemask and their
potential long-term consequences for health.

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In addition to hypoxia and hypercapnia, breathing through facemask residues bacterial and
germs components on the inner and outside layer of the facemask. These toxic components are
repeatedly rebreathed back into the body, causing self-contamination. Breathing through
facemasks also increases temperature and humidity in the space between the mouth and the
mask, resulting a release of toxic particles from the mask’s materials [1], [2], [19], [26], [35], [36].
A systematic literature review estimated that aerosol contamination levels of facemasks
including 13 to 202,549 different viruses [1]. Rebreathing contaminated air with high bacterial
and toxic particle concentrations along with low O2 and high CO2 levels continuously challenge
the body homeostasis, causing self-toxicity and immunosuppression [1], [2], [19], [26], [35], [36].
A study on 39 patients with renal disease found that wearing N95 facemask during hemodialysis
significantly reduced arterial partial oxygen pressure (from PaO2 101.7 to 92.7 mm Hg),
increased respiratory rate (from 16.8 to 18.8 breaths/min), and increased the occurrence of
chest discomfort and respiratory distress [35]. Respiratory Protection Standards from
Occupational Safety and Health Administration, US Department of Labor states that breathing
air with O2 concentration below 19.5% is considered oxygen-deficiency, causing physiological
and health adverse effects. These include increased breathing frequency, accelerated heartrate
and cognitive impairments related to thinking and coordination [36]. A chronic state of mild
hypoxia and hypercapnia has been shown as primarily mechanism for developing cognitive
dysfunction based on animal studies and studies in patients with chronic obstructive pulmonary
disease [44].
The adverse physiological effects were confirmed in a study of 53 surgeons where surgical
facemask were used during a major operation. After 60 min of facemask wearing the oxygen
saturation dropped by more than 1% and heart rate increased by approximately five beats/min
[45]. Another study among 158 health-care workers using protective personal equipment
primarily N95 facemasks reported that 81% (128 workers) developed new headaches during
their work shifts as these become mandatory due to COVID-19 outbreak. For those who used
the N95 facemask greater than 4 h per day, the likelihood for developing a headache during the
work shift was approximately four times higher [Odds ratio = 3.91, 95% CI (1.35–11.31) p =
0.012], while 82.2% of the N95 wearers developed the headache already within ≤10 to 50 min
[46].
With respect to cloth facemask, a RCT using four weeks follow up compared the effect of cloth
facemask to medical masks and to no masks on the incidence of clinical respiratory illness,
influenza-like illness and laboratory-confirmed respiratory virus infections among 1607
participants from 14 hospitals [19]. The results showed that there were no difference between
wearing cloth masks, medical masks and no masks for incidence of clinical respiratory illness
and laboratory-confirmed respiratory virus infections. However, a large harmful effect with more
than 13 times higher risk [Relative Risk = 13.25 95% CI (1.74 to 100.97) was observed for
influenza-like illness among those who were wearing cloth masks [19]. The study concluded
that cloth masks have significant health and safety issues including moisture retention, reuse,
poor filtration and increased risk for infection, providing recommendation against the use of
cloth masks [19].

Psychological effects of wearing facemasks
Psychologically, wearing facemask fundamentally has negative effects on the wearer and the
nearby person. Basic human-to-human connectivity through face expression is compromised
and self-identity is somewhat eliminated [47], [48], [49]. These dehumanizing movements
partially delete the uniqueness and individuality of person who wearing the facemask as well as
the connected person [49]. Social connections and relationships are basic human needs, which
innately inherited in all people, whereas reduced human-to-human connections are associated
with poor mental and physical health [50], [51]. Despite escalation in technology and
globalization that would presumably foster social connections, scientific findings show that
people are becoming increasingly more socially isolated, and the prevalence of loneliness is
increasing in last few decades [50], [52]. Poor social connections are closely related to isolation
and loneliness, considered significant health related risk factors [50], [51], [52], [53].

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A meta-analysis of 91 studies of about 400,000 people showed a 13% increased morality risk
among people with low compare to high contact frequency [53]. Another meta-analysis of 148
prospective studies (308,849 participants) found that poor social relationships was associated
with 50% increased mortality risk. People who were socially isolated or fell lonely had 45% and
40% increased mortality risk, respectively. These findings were consistent across ages, sex,
initial health status, cause of death and follow-up periods [52]. Importantly, the increased risk for
mortality was found comparable to smoking and exceeding well-established risk factors such as
obesity and physical inactivity [52]. An umbrella review of 40 systematic reviews including 10
meta-analyses demonstrated that compromised social relationships were associated with
increased risk of all-cause mortality, depression, anxiety suicide, cancer and overall physical
illness [51].
As described earlier, wearing facemasks causing hypoxic and hypercapnic state that constantly
challenges the normal homeostasis, and activates “fight or flight” stress response, an important
survival mechanism in the human body [11], [12], [13]. The acute stress response includes
activation of nervous, endocrine, cardiovascular, and the immune systems [47], [54], [55], [56].
These include activation of the limbic part of the brain, release stress hormones (adrenalin,
neuro-adrenalin and cortisol), changes in blood flow distribution (vasodilation of peripheral blood
vessels and vasoconstriction of visceral blood vessels) and activation of the immune system
response (secretion of macrophages and natural killer cells) [47], [48]. Encountering people who
wearing facemasks activates innate stress-fear emotion, which is fundamental to all humans in
danger or life threating situations, such as death or unknown, unpredictable outcome. While
acute stress response (seconds to minutes) is adaptive reaction to challenges and part of the
survival mechanism, chronic and prolonged state of stress-fear is maladaptive and has
detrimental effects on physical and mental health. The repeatedly or continuously activated
stress-fear response causes the body to operate on survival mode, having sustain increase in
blood pressure, pro-inflammatory state and immunosuppression [47], [48].

Long-Term health consequences of wearing facemasks
Long-term practice of wearing facemasks has strong potential for devastating health
consequences. Prolonged hypoxic-hypercapnic state compromises normal physiological and
psychological balance, deteriorating health and promotes the developing and progression of
existing chronic diseases [23], [38], [39], [43], [47], [48], [57], [11], [12], [13]. For instance,
ischemic heart disease caused by hypoxic damage to the myocardium is the most common
form of cardiovascular disease and is a number one cause of death worldwide (44% of all noncommunicable diseases) with 17.9 million deaths occurred in 2016 [57]. Hypoxia also playing an
important role in cancer burden [58]. Cellular hypoxia has strong mechanistic feature in
promoting cancer initiation, progression, metastasis, predicting clinical outcomes and usually
presents a poorer survival in patients with cancer. Most solid tumors present some degree of
hypoxia, which is independent predictor of more aggressive disease, resistance to cancer
therapies and poorer clinical outcomes [59], [60]. Worth note, cancer is one of the leading
causes of death worldwide, with an estimate of more than 18 million new diagnosed cases and
9.6 million cancer-related deaths occurred in 2018 [61].
With respect to mental health, global estimates showing that COVID-19 will cause a catastrophe
due to collateral psychological damage such as quarantine, lockdowns, unemployment,
economic collapse, social isolation, violence and suicides [62], [63], [64]. Chronic stress along
with hypoxic and hypercapnic conditions knocks the body out of balance, and can cause
headaches, fatigue, stomach issues, muscle tension, mood disturbances, insomnia and
accelerated aging [47], [48], [65], [66], [67]. This state suppressing the immune system to
protect the body from viruses and bacteria, decreasing cognitive function, promoting the
developing and exacerbating the major health issues including hypertension, cardiovascular
disease, diabetes, cancer, Alzheimer disease, rising anxiety and depression states, causes
social isolation and loneliness and increasing the risk for prematurely mortality [47], [48], [51],
[56], [66].

6

Conclusion
The existing scientific evidences challenge the safety and efficacy of wearing facemask as
preventive intervention for COVID-19. The data suggest that both medical and non-medical
facemasks are ineffective to block human-to-human transmission of viral and infectious disease
such SARS-CoV-2 and COVID-19, supporting against the usage of facemasks. Wearing
facemasks has been demonstrated to have substantial adverse physiological and psychological
effects. These include hypoxia, hypercapnia, shortness of breath, increased acidity and toxicity,
activation of fear and stress response, rise in stress hormones, immunosuppression, fatigue,
headaches, decline in cognitive performance, predisposition for viral and infectious illnesses,
chronic stress, anxiety and depression. Long-term consequences of wearing facemask can
cause health deterioration, developing and progression of chronic diseases and premature
death. Governments, policy makers and health organizations should utilize prosper and
scientific evidence-based approach with respect to wearing facemasks, when the latter is
considered as preventive intervention for public health.

Credit authorship contribution statement
Baruch Vainshelboim: Conceptualization, Data curation, Writing – original draft.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.

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