The Centers for Disease Control has said that a study shows that the wearing of two cloth face masks reduces Covid vulnerability. Yet this doesn't seem to square with studies that found that even sweatshirt cloth and towel cloth weren't much good at blocking airborne particles.
Even the N95 masks are far from perfect, studies found. They may not screen out particles below a certain size. Virus particles are extremely small.
Below is a bar graph for N95 masks versus cloth. All "cloth" bars tower above the barely visible "N95" bar.
Science Direct, which is run by China-based Ke-Ai, reports that studies disclose that "wearing of cloth masks will not have much effect."
At present, Chinese authorities publish statistics saying that Covid has been virtually eliminated, implying that the public is not under pressure to wear masks.
A New York Times report has suggested that the worldwide pressure to wear cloth masks is related to
China's Uighur slave-labor plants, which have been producing large numbers of them.
Article by A. Tcharkhtchia et al
https://www.sciencedirect.com/science/article/pii/S2452199X20301481
From that article:
2.3. Comparison of different masks
As discussed in the section of cloth masks, Rengasamy et al. [17] indicated that the penetration of cloth masks is more than N95, and it means that wearing cloth masks will not have much effect.
A. Tcharkhtchia, N. Abbasnezhadab, M. Zarbini, Seydanib, N. Zirakb, S. Farzanehc, M. Shirinbayanab
Unless your mask includes an airborne particle filter, it won't do much. That is, the mask should have crushed glass or other "catchers" on its surface and be made of extremely finely woven material.
Article by G.J. Curiel, H.L.M. Lelieveld
https://www.sciencedirect.com/topics/engineering/air-filtration
G.J. Curiel and H.L.M. Lelieveld are both widely published in the field of hygiene technology.
Further, another study found that masks can be hazardous because wearers breathe in microplastic fibers, according to a Jan. 2 news report from Beijing.
In Hong Kong's South China Morning Post, Stephen Chen reported that a Chinese study had found that "most masks shed microplastic fibres that are inhaled by the wearer and could be harmful."
Chen then added a disclaimer asserting that studies had shown that people should wear masks anyway.
And a study by scientists in Scotland raised serious doubts as to the effectiveness of masks provided to residents of Beijing, finding that a major problem was that masks were ill-fitting. The scientists urged that better information be provided to the public.
Article by John W. Cherrie et al
https://oem.bmj.com/content/75/6/446
Abstract
Objectives Many residents in Beijing use disposable face masks in an attempt to protect their health from high particulate matter (PM) concentrations. Retail masks may be certified to local or international standards, but their real-life performance may not confer the exposure reduction potential that is marketed. This study aimed to evaluate the effectiveness of a range of face masks that are commercially available in China.
Methods Nine masks claiming protection against fine PM (PM2.5) were purchased from consumer outlets in Beijing. The masks’ filtration efficiency was tested by drawing airborne diesel exhaust through a section of the material and measuring the PM2.5 and black carbon (BC) concentrations upstream and downstream of the filtering medium. Four masks were selected for testing on volunteers. Volunteers were exposed to diesel exhaust inside an experimental chamber while performing sedentary tasks and active tasks. BC concentrations were continuously monitored inside and outside the mask.
Results The mean per cent penetration for each mask material ranged from 0.26% to 29%, depending on the flow rate and mask material. In the volunteer tests, the average total inward leakage (TIL) of BC ranged from 3% to 68% in the sedentary tests and from 7% to 66% in the active tests. Only one mask type tested showed an average TIL of less than 10%, under both test conditions.
Conclusions Many commercially available face masks may not provide adequate protection, primarily due to poor facial fit. Our results indicate that further attention should be given to mask design and providing evidence-based guidance to consumers.
John W Cherrie, Andrew Apsley, Hilary Cowie, Susanne Steinli, William Mueller, Anne Sleeuwenhoek, Miranda Loh:
Institute of Occupational Medicine, Centre for Human Exposure Science, Edinburgh, UK
Cherrie:
Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Edinburgh, UK
Chun Lin:
School of Chemistry, University of Edinburgh, Edinburgh, UK
Claire J. Horwell:
Department of Earth Sciences, Institute of Hazard, Risk and Resilience, Durham University, Durham, UK
But, would N95 masks be appropriate for the public? Two Chinese scientists found that such masks dramatically restrict air flow.
Hence, they result in considerable discomfort for patients with breathing difficulties and even health workers whose breathing may be sub-par.
Even cloth masks are found to restrict oxygen intake for members of the public, many of them middle-aged or older. That is, those who are the most vulnerable to Covid and other respiratory diseases are least able to tolerate extended mask-wearing.
Article by Heow Pueh Lee and De Yun Wang
https://academic.oup.com/annweh/article/55/8/917/265317
Abstract
Face masks or respirators are commonly worn by medical professionals and patients for protection against respiratory tract infection and the spread of illnesses, such as severe acute respiratory syndrome and pandemic influenza (H1N1). Breathing discomfort due to increased breathing resistance is known to be a problem with the use of N95 respirators but there is a lack of scientific data to quantify this effect. The purpose of this study was to assess objectively the impact of wearing N95 face masks on breathing resistance. A total of 14 normal adult volunteers (seven males and seven females) were recruited in this study. Nasal airflow resistance during inspiration and expiration was measured using a standard rhinomanometry and nasal spirometry. A modified full face mask was produced in-house in order to measure nasal resistance with the use of N95 (3M 8210) respirators. The results showed a mean increment of 126 and 122% in inspiratory and expiratory flow resistances, respectively, with the use of N95 respirators. There was also an average reduction of 37% in air exchange volume with the use of N95 respirators. This is the first reported study that demonstrates quantitatively and objectively the substantial impairment of nasal airflow in terms of increased breathing resistance with the use of N95 respirators on actual human subjects.
Annals of Work Exposure and Health, an Oxford Academic journal
Heow Pueh Lee
Department of Mechanical Engineering, National University of Singapore,
De Yun Wang
Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore
