Un studiu recent publicat in jurnalul „Cancer Discovery” a demonstrat că inhalarea de microbi nocivi poate contribui la forme avansate de cancer pulmonar la adulți. Purtarea îndelungată a măștilor faciale poate ajuta la înmulțirea acestor agenți patogeni.
Microbiologii sunt de acord că purtarea frecventă a măștii crează un mediu umed în care microbilor li se permite să se înmulțească și să prolifereze înainte de a pătrunde în plămâni. Acești microbi străini circulă în jos pe trahee și pe cele două tuburi numite bronhii până când ajung la acei săculeți de aer acoperiți de vase sangvine numiți alveole.
„Mult timp s-a crezut că plămânii sunt sterili dar acum știm că microbii orali comensuali, prezenți în mod frecvent în cavitatea bucală, pătrund în plămâni din cauza unor aspirații inconștiente” – Leopoldo Segal, autorul studiului, director al Programului privind Microbiomul Pulmonar și profesor asociat de medicină la Școala Grossman de Medicină a Universității New York.
Potrivit studiului, după invadarea plămânilor, acești microbi provoacă un răspuns inflamator în proteinele cunoscute ca citokinele IL-17.
„Fiind cunoscut impactul produs de IL-17 și inflamația în cancerul pulmonar, am fost interesați în a determina dacă înmulțirea comensualilor orali în plămâni ar putea duce la o inflamare de tip IL-17 și ar putea influența prognoza și progresul cancerului pulmonar”, a mai spus Segal.
Analizând microbii pulmonari a 83 de adulți cu cancer pulmonar netratat, echipa de cercetare a descoperit că coloniile de Veillonella, Prevotella și streptococi și care pot fi cultivate prin purtarea prelungită a măștilor, se găsesc în cantități mai mari în plămânii pacienților cu cancer în stadiu avansat decât în cei aflați în faze incipiente. Prezența acestor culturi de bacterii este asociată de asemenea cu o șansă mai scăzută de supraviețuire și o rata de creștere a tumorilor mai ridicată, indiferent de stadiu.
Suplimentar, cercetările privind cultivarea bacteriei Veillonella în plămânii șoarecilor a relevat faptul că prezența acestei bacterii duce la apariția celulelor imuno-supresoare dar și a inflamațiilor de tipul citokinei IL-17.
„Luând în considerare rezultatele studiului nostru, este posibil ca schimbări ale microbiomului pulmonar să fie folosite ca biomarkeri pentru a prognoza sau programa pacienții pentru tratament” – Leopoldo Segal.
Pe măsură ce tot mai multe dovezi apar cu privire la efectele pe termen lung ale purtării măștii și carantinării, doctorii și oamenii de știință încep să-și reconsidere părerea dacă nu cumva măsurile autoritariste fac mai mult rău decât bine. Un expert canadian în sănătate publică, Dr. Aji Joffe, a descoperit într-un studiu pe acest subiect că etapele de carantină produc „cel puțin de zece ori” mai multe pagube decât beneficii.
Într-un document recent aparținând unor cercetători de la universitățile Harvard, Duke și John Hopkins, oamenii de știință au concluzionat că „la nivelul întregii populații, creșterea ratei mortalității după pandemia de COVID-19 implică un nivel infricoșător de 0,89 și, respectiv, 1,37 milioane de decese în plus în următorii 15 – 20 de ani.”
Din momentul în care s-a impus purtarea măștii, dermatologii au patentat, la rândul lor, termenul de „mascnee” pentru a descrie o erupție de coșuri în apropierea gurii provocată de obturarea porilor de către mască și înfundarea lor cu grăsimi și bacterii.
Stomatologii au avertizat și ei în privința unui fenomen numit „gură de mască” în care pacienții se întorc la cabinetul stomatologic cu un număr crescut de gingivite și carii dentare – până la 50% mai mult – într-o perioadă de numai câteva luni de la instituirea obligativității purtării măștii.
Această descoperire aduce mai multă lumină asupra numărului crescut de dovezi asupra nocivității purtării măștii pe timp îndelungat.
It found: “Compared to no masks, there was no reduction of influenza-like illness cases or influenza for masks in the general population, nor in healthcare workers.”
This 2020 meta-analysis found that evidence from randomized controlled trials of face masks did not support a substantial effect on transmission of laboratory-confirmed influenza, either when worn by infected persons (source control) or by persons in the general community to reduce their susceptibility.
2.) J Xiao, E Shiu, et al. Nonpharmaceutical measures for pandemic influenza in non-healthcare settings – personal protective and environmental measures. Centers for Disease Control. 26(5); 2020 May.
Another recent review found that masks had no effect specifically against Covid-19, although facemask use seemed linked to, in 3 of 31 studies, “very slightly reduced” odds of developing influenza-like illness.
3.) J Brainard, N Jones, et al. Facemasks and similar barriers to prevent respiratory illness such as COVID19: A rapid systematic review. MedRxiv. 2020 Apr 1.
This 2016 meta-analysis found that both randomized controlled trials and observational studies of N95 respirators and surgical masks used by healthcare workers did not show benefit against transmission of acute respiratory infections. It was also found that acute respiratory infection transmission “may have occurred via contamination of provided respiratory protective equipment during storage and reuse of masks and respirators throughout the workday.”
5.) J Smith, C MacDougall. CMAJ. 2016 May 17. 188(8); 567-574.
A 2011 meta-analysis of 17 studies regarding masks and effect on transmission of influenza found that “none of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”
6.) F bin-Reza, V Lopez, et al. The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence. 2012 Jul; 6(4): 257-267.
However, authors speculated that effectiveness of masks may be linked to early, consistent and correct usage. Face mask use was likewise found to be not protective against the common cold, compared to controls without face masks among healthcare workers.
7.) J Jacobs, S Ohde, et al. Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial. Am J Infect Control. 2009 Jun; 37(5): 417-419.
Airflow around masks. Masks have been assumed to be effective in obstructing forward travel of viral particles. Considering those positioned next to or behind a mask wearer, there have been farther transmission of virus-laden fluid particles from masked individuals than from unmasked individuals, by means of “several leakage jets, including intense backward and downwards jets that may present major hazards,” and a “potentially dangerous leakage jet of up to several meters.”
8.) M Viola, B Peterson, et al. Face coverings, aerosol dispersion and mitigation of virus transmission risk.
All masks were thought to reduce forward airflow by 90% or more over wearing no mask. However, Schlieren imaging showed that both surgical masks and cloth masks had farther brow jets (unfiltered upward airflow past eyebrows) than not wearing any mask at all, 182 mm and 203 mm respectively, vs none discernible with no mask. Backward unfiltered airflow was found to be strong with all masks compared to not masking.
For both N95 and surgical masks, it was found that expelled particles from 0.03 to 1 micron were deflected around the edges of each mask, and that there was measurable penetration of particles through the filter of each mask.
9.) S Grinshpun, H Haruta, et al. Performance of an N95 filtering facepiece particular respirator and a surgical mask during human breathing: two pathways for particle penetration. J Occup Env Hygiene. 2009; 6(10):593-603.
Penetration through masks. A study of 44 mask brands found mean 35.6% penetration (+ 34.7%). Most medical masks had over 20% penetration, while “general masks and handkerchiefs had no protective function in terms of the aerosol filtration efficiency.” The study found that “Medical masks, general masks, and handkerchiefs were found to provide little protection against respiratory aerosols.”
10.) H Jung, J Kim, et al. Comparison of filtration efficiency and pressure drop in anti-yellow sand masks, quarantine masks, medical masks, general masks, and handkerchiefs. Aerosol Air Qual Res. 2013 Jun. 14:991-1002.
It may be helpful to remember that an aerosol is a colloidal suspension of liquid or solid particles in a gas. In respiration, the relevant aerosol is the suspension of bacterial or viral particles in inhaled or exhaled breath.
In another study, penetration of cloth masks by particles was almost 97% and medical masks 44%.
11.) C MacIntyre, H Seale, et al. A cluster randomized trial of cloth masks compared with medical masks in healthcare workers. BMJ Open. 2015; 5(4)
N95 respirators are so named, because 95% of particles having a diameter of 0.3 microns are filtered by the mask forward of the wearer, by use of an electrostatic mechanism. Coronaviruses are approximately 0.125 microns in diameter.
This meta-analysis found that N95 respirators did not provide superior protection to facemasks against viral infections or influenza-like infections.
13.) V Offeddu, C Yung, et al. Effectiveness of masks and respirators against infections in healthcare workers: A systematic review and meta-analysis. Clin Inf Dis. 65(11), 2017 Dec 1; 1934-1942.
This study did find superior protection by N95 respirators when they were fit-tested compared to surgical masks.
14.) C MacIntyre, Q Wang, et al. A cluster randomized clinical trial comparing fit-tested and non-fit-tested N95 respirators to medical masks to prevent respiratory virus infection in health care workers. Influenza J. 2010 Dec 3.
Surgical masks. This study found that surgical masks offered no protection at all against influenza.
16.) C MacIntyre, Q Wang, et al. A cluster randomized clinical trial comparing fit-tested and non-fit-tested N95 respirators to medical masks to prevent respiratory virus infection in health care workers. Influenza J. 2010 Dec 3.
Another study found that surgical masks had about 85% penetration ratio of aerosolized inactivated influenza particles and about 90% of Staphylococcus aureus bacteria, although S aureus particles were about 6x the diameter of influenza particles.
17.) N Shimasaki, A Okaue, et al. Comparison of the filter efficiency of medical nonwoven fabrics against three different microbe aerosols. Biocontrol Sci. 2018; 23(2). 61-69.
Specifically, are surgical masks effective in stopping human transmission of coronaviruses? Both experimental and control groups, masked and unmasked respectively, were found to “not shed detectable virus in respiratory droplets or aerosols.”
23.) N Leung, D Chu, et al. Respiratory virus shedding in exhaled breath and efficacy of face masks Nature Research. 2020 Mar 7. 26,676-680 (2020).
In that study, they “did not confirm the infectivity of coronavirus” as found in exhaled breath.
A study of aerosol penetration showed that two of the five surgical masks studied had 51% to 89% penetration of polydisperse aerosols.
24.) S Rengasamy, B Eimer, et al. Simple respiratory protection – evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Ann Occup Hyg. 2010 Oct; 54(7): 789-798.
In another study, that observed subjects while coughing, “neither surgical nor cotton masks effectively filtered SARS-CoV-2 during coughs by infected patients.” And more viral particles were found on the outside than on the inside of masks tested.
25.) S Bae, M Kim, et al. Effectiveness of surgical and cotton masks in blocking SARS-CoV-2: A controlled comparison in 4 patients. Ann Int Med. 2020 Apr 6.
Cloth masks were found to have low efficiency for blocking particles of 0.3 microns and smaller. Aerosol penetration through the various cloth masks examined in this study were between 74 and 90%. Likewise, the filtration efficiency of fabric materials was 3% to 33%
26.) S Rengasamy, B Eimer, et al. Simple respiratory protection – evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Ann Occup Hyg. 2010 Oct; 54(7): 789-798.
This 1920 analysis of cloth mask use during the 1918 pandemic examines the failure of masks to impede or stop flu transmission at that time, and concluded that the number of layers of fabric required to prevent pathogen penetration would have required a suffocating number of layers, and could not be used for that reason, as well as the problem of leakage vents around the edges of cloth masks.
29.) M Klompas, C Morris, et al. Universal masking in hospitals in the Covid-19 era. N Eng J Med. 2020; 382 e63.
Masks against Covid-19. The New England Journal of Medicine editorial on the topic of mask use versus Covid-19 assesses the matter as follows:
“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 20 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.”
30.) E Person, C Lemercier et al. Effect of a surgical mask on six minute walking distance. Rev Mal Respir. 2018 Mar; 35(3):264-268.
Researchers are concerned about possible burden of facemasks during physical activity on pulmonary, circulatory and immune systems, due to oxygen reduction and air trapping reducing substantial carbon dioxide exchange. As a result of hypercapnia, there may be cardiac overload, renal overload, and a shift to metabolic acidosis.
32.) P Shuang Ye Tong, A Sugam Kale, et al. Respiratory consequences of N95-type mask usage in pregnant healthcare workers – A controlled clinical study. Antimicrob Resist Infect Control. 2015 Nov 16; 4:48.
Risks of N95 respirators. Pregnant healthcare workers were found to have a loss in volume of oxygen consumption by 13.8% compared to controls when wearing N95 respirators. 17.7% less carbon dioxide was exhaled.
33.) T Kao, K Huang, et al. The physiological impact of wearing an N95 mask during hemodialysis as a precaution against SARS in patients with end-stage renal disease. J Formos Med Assoc. 2004 Aug; 103(8):624-628.
Patients with end-stage renal disease were studied during use of N95 respirators. Their partial pressure of oxygen (PaO2) decreased significantly compared to controls and increased respiratory adverse effects.
33.) F Blachere, W Lindsley et al. Assessment of influenza virus exposure and recovery from contaminated surgical masks and N95 respirators. J Viro Methods. 2018 Oct; 260:98-106.
(Surgical masks were also found to be a repository of bacterial contamination. The source of the bacteria was determined to be the body surface of the surgeons, rather than the operating room environment.
39.) C MacIntyre, H Seale, et al. A cluster randomized trial of cloth masks compared with medical masks in healthcare workers. BMJ Open. 2015; 5(4)
Given that surgeons are gowned from head to foot for surgery, this finding should be especially concerning for laypeople who wear masks. Without the protective garb of surgeons, laypeople generally have even more exposed body surface to serve as a source for bacteria to collect on their masks.
Risks of cloth masks: Healthcare workers wearing cloth masks had significantly higher rates of influenza-like illness after four weeks of continuous on-the-job use, when compared to controls.
40.) A Beder, U Buyukkocak, et al. Preliminary report on surgical mask induced deoxygenation during major surgery. Neurocirugia. 2008; 19: 121-126.
The increased rate of infection in mask-wearers may be due to a weakening of immune function during mask use. Surgeons have been found to have lower oxygen saturation after surgeries even as short as 30 minutes.
41.) D Lukashev, B Klebanov, et al. Cutting edge: Hypoxia-inducible factor 1-alpha and its activation-inducible short isoform negatively regulate functions of CD4+ and CD8+ T lymphocytes. J Immunol. 2006 Oct 15; 177(8) 4962-4965.
This in turn down-regulates CD4+ T-cells. CD4+ T-cells, in turn, are necessary for viral immunity (42). Hypoxia negatively regulates functions of CD4+ and CD8+ T lymphocites (41)
43.) C Raina MacIntyre, Holly Seale, Tham Chi Dung. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open. 2015; 5(4): e006577. DOI: 10.1136/bmjopen-2014-006577
Over 3 times the risk of contracting influenza like illness if cloth mask is used. Penetration of cloth masks by particles was almost 97% compared to medical masks with 44%. „These guidelines need to be updated to reflect the higher infection risk posed by cloth masks, as found in our study.”
44.) Shane Neilson, MD, PhD. The surgical mask is a bad fit for risk reduction. CMAJ. 2016 May 17; 188(8): 606–607. doi: 10.1503/cmaj.151236
45.) Y. Li, H. Tokura, Y.P. Guo, A.S.W. Wong. Effects of wearing N95 and surgical facemasks on heartrate, thermal stress, and subjective sensations. Int Arch Occup Environ Health. 2005; 78(6): 501–509. doi: 10.1007/s00420-004-0584-4
In the summer of 2020 the United States is experiencing a surge of popular mask use, which is frequently promoted by the media, political leaders and celebrities. Homemade and store-bought cloth masks and surgical masks or N95 masks are being used by the public especially when entering stores and other publicly accessible buildings. Sometimes bandanas or scarves are used. The use of face masks, whether cloth, surgical or N95, creates a poor obstacle to aerosolized pathogens as we can see from the meta-analyses and other studies in this paper, allowing both transmission of aerosolized pathogens to others in various directions, as well as self-contamination.
It must also be considered that masks impede the necessary volume of air intake required for adequate oxygen exchange, which results in observed physiological effects that may be undesirable. Even 6- minute walks, let alone more strenuous activity, resulted in dyspnea. The volume of unobstructed oxygen in a typical breath is about 100 ml, used for normal physiological processes. 100 ml O2 greatly exceeds the volume of a pathogen required for transmission.
The foregoing data show that masks serve more as instruments of obstruction of normal breathing, rather than as effective barriers to pathogens. Therefore, masks should not be used by the general public, either by adults or children, and their limitations as prophylaxis against pathogens should also be considered in medical settings.