Why Masks Don't Work - A Resource Guide
I am putting this resource guide down for those who wish to understand why masks do not work generally at stopping cold-family viruses.
COMMENTARY: Masks-for-all for COVID-19 not based on sound data
• The filter performance of a cloth material does not directly translate or represent its performance on an individual, because it neglects the understanding of fit.
• Cloth masks or coverings come in a variety of shapes, sizes, and materials and are not made according to any standards.
• Transmission is not simply a function of short random interactions between individuals, but rather a function of particle concentration in the air and the time exposed to that concentration.
• A cloth mask or face covering does very little to prevent the emission or inhalation of small particles. As discussed in an earlier CIDRAP commentary and more recently by Morawska and Milton (2020) in an open letter to WHO signed by 239 scientists, inhalation of small infectious particles is not only biologically plausible, but the epidemiology supports it as an important mode of transmission for SARS-CoV-2, the virus that causes COVID-19.
Are Face Masks Effective? The Evidence.
https://swprs.org/face-masks-evidence/
Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks
https://pubs.acs.org/doi/10.1021/acsnano.0c03252
A cluster randomised trial of cloth masks compared with medical masks in healthcare workers
2015: https://bmjopen.bmj.com/content/5/4/e006577
Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis
2016: https://www.cmaj.ca/content/188/8/567
2017: https://academic.oup.com/cid/article/65/11/1934/4068747
2019: https://jamanetwork.com/journals/jama/fullarticle/2749214
2020: https://onlinelibrary.wiley.com/doi/epdf/10.1111/jebm.12381
In our systematic review, we identified 10 RCTs that reported estimates of the effectiveness of face masks in reducing laboratory-confirmed influenza virus infections in the community from literature published during 1946–July 27, 2018. In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.78, 95% CI 0.51–1.20; I2 = 30%, p = 0.25) (Figure 2). One study evaluated the use of masks among pilgrims from Australia during the Hajj pilgrimage and reported no major difference in the risk for laboratory-confirmed influenza virus infection in the control or mask group (33). Two studies in university settings assessed the effectiveness of face masks for primary protection by monitoring the incidence of laboratory-confirmed influenza among student hall residents for 5 months (9,10). The overall reduction in ILI or laboratory-confirmed influenza cases in the face mask group was not significant in either studies (9,10). Study designs in the 7 household studies were slightly different: 1 study provided face masks and P2 respirators for household contacts only (34), another study evaluated face mask use as a source control for infected persons only (35), and the remaining studies provided masks for the infected persons as well as their close contacts (11–13,15,17). None of the household studies reported a significant reduction in secondary laboratory-confirmed influenza virus infections in the face mask group (11–13,15,17,34,35). Most studies were underpowered because of limited sample size, and some studies also reported suboptimal adherence in the face mask group.
A cluster randomised trial of cloth masks compared with medical masks in healthcare workers
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/?fbclid=IwAR1wBoO2Ss5nruUhZ6ssf1Pw79u84HGKcRubthRWPEKB3b5yjAtJy9kMzKA#R19
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
Do N95 respirators provide 95% protection level against airborne
viruses, and how adequate are surgical masks?
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.488.4644&rep=rep1&type=pdf
Effectiveness of facemasks to reduce exposure hazards for airborne infections among general populations
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306645/
Masks worn by patients may not offer as great a degree of protection against aerosol transmission.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/#:~:text=Short%20term%20inward%20protection%20experiment&text=Surgical%20masks%20provided%20about%20twice,much%20protection%20as%20surgical%20masks.
Results The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%.
https://bmjopen.bmj.com/content/5/4/e006577
This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.