Have masks been effective at preventing transmission?

Much of the research prior to COVID and in the first half of 2020 concluded that masks were not effective for preventing transmission of aerosolized viruses.

Research has also shown that mask-wearing can cause harm to the wearer.

Unfortunately, like many issues, science and therefore policy can be influenced by financial and political interests. Since the middle of last year, many authorities who originally stated that masks were unnecessary and ineffective, flipped their positions…

On March 12th, 2021, the CDC published the following report on their website:

Association of State-Issued Mask Mandates and Allowing On-Premises Restaurant Dining with County-Level COVID-19 Case and Death Growth Rates — United States, March 1–December 31, 2020.

With regard to evaluating the effectiveness of mask mandates on COVID case and death counts, the CDC states:

“Mask mandates were associated with a 0.5 percentage point decrease (p = 0.02) in daily COVID-19 case growth rates 1–20 days after implementation and decreases of 1.1, 1.5, 1.7, and 1.8 percentage points 21–40, 41–60, 61–80, and 81–100 days, respectively, after implementation…

Mask mandates were associated with a 0.7 percentage point decrease (p = 0.03) in daily COVID-19 death growth rates 1–20 days after implementation and decreases of 1.0, 1.4, 1.6, and 1.9 percentage points 21–40, 41–60, 61–80, and 81–100 days, respectively…”

To reiterate:

The CDC calculates that mask mandates were associated (correlated) with a 1.9% decrease in the growth rates of COVID deaths over a time period of 100 days, post-mask mandates.

What can we take away from this? Is a 1.9% effect on the growth rate even truly significant?

The CDC fails to account for other variables which undeniably impacted case and death counts. Most notably, mask mandates would have changed shopping habits for individuals who did not want to wear masks in order to purchase groceries, and less people would also be using public restrooms.

Side note: There has been controversy previously over whether the most important route of transmission of COVID may actually be fecal-oral. Much more on this topic, here.

Claiming that mask mandates and therefore, mask-wearing, was responsible for a 1.9% decline in the growth rates of COVID deaths while ignoring other variables is turning a blind eye to their own catch phrase: “correlation does not equal causation”.

(2021) https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm?s_cid=mm7010e3_w

With regard to safety, a relatively recent study has raised concern that masks may be causing damage to the human respiratory tract and may increase the risk of viral infection:

Need for assessing the inhalation of micro(nano)plastic debris shed from masks, respirators, and home-made face coverings during the COVID-19 pandemic.

“Respirable hazards such as micro(nano)plastics present in [masks] may escalate from once an occupational hazard to a public health issue.”

“Going further, investigations will need to be done on whether the debris will cause stress or inflammation in human respiratory tract and exacerbate vulnerability of viral infection.”

“[C]omplaints of throat irritation or discomfort in the respiratory tract by children, the elderly, or other sensitive individuals after wearing these may be alerting signs of excessive amounts of respirable debris inhaled from self-made masks and respirators…”

(2020) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7537728/

Additional studies and articles regarding the safety and effectiveness of wearing masks is presented below:

Cloth masks: Dangerous to your health?

“Respiratory infection is much higher among healthcare workers wearing cloth masks compared to medical masks, research shows. Cloth masks should not be used by workers in any healthcare setting, authors of the new study say.”

Article quote above is based on the following study: A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.

“The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI [influenza-like illness] statistically significantly higher in the cloth mask 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%.”

“Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.”

(2015) https://www.sciencedaily.com/releases/2015/04/150422121724.htm / https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ / https://bmjopen.bmj.com/content/5/4/e006577

During Hemodialysis: 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 [low blood oxygen]. Wearing an N95 mask significantly reduced the PaO2 level and increased respiratory adverse effects…”

(2004) https://www.ncbi.nlm.nih.gov/pubmed/15340662

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.”

(2008) https://www.ncbi.nlm.nih.gov/pubmed/18500410

Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks?

“Viral particles, or virions, are one of the smallest known bioaerosol agents, with a particle diameter ranging from 20 to 300nm.”

Regarding the size of virions and penetration of N95 masks: 

“Similar results were reported by Martin and Moyer, who found that the maximum penetration of particles through the fiber-charged N95 respirators occurred in the 50- to 100-nm size range. Thus it should be emphasized that the certified N95 respirators will protect their wearers properly against the particles of 300 nm and larger, but their performance may be be- low the threshold for aerosol particles of the nanosize range.”

For one of the surgical masks tested, “the penetration increases with increasing particle size to 84.5% for particles of 80 nm in diameter…”

“The penetration data presented in this paper were obtained using manikin-based tests. Thus, the respirators and surgical masks were sealed to the manikin’s face. Such procedure eliminated the leakages, which can occur when a subject wears the personal respiratory protection devices.

In real life, the leaks may lead to considerably increased particles penetration. …without proper fit testing, the wearer of a respirator cannot achieve the desired protection level.”

“The results indicate that N95-certified respirators may not necessarily provide a proper protection against virus, which is considerably smaller than the accepted most penetrating particle size of 300 nm used in the certification tests.”

“The N95 filtering face piece respirators may not provide the expected protection level against small virions. Some surgical masks may let a significant fraction of airborne viruses penetrate through their filters, providing very low protection against aerosolized infectious agents in the size range of 10 to 80 nm.”

(2006) https://www.ajicjournal.org/article/S0196-6553(05)00911-9/fulltext

Headaches Associated With Personal Protective Equipment – A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19.

81.0% of respondents developed de novo PPE [mask] -associated headaches.

(2020) https://pubmed.ncbi.nlm.nih.gov/32232837/

Evaluation of rebreathed air in human nasal cavity with N95 respirator: a CFD study

The above study found that 60% of inspired air, is respired air, when wearing a properly fitted N95 mask.

OSHA Respiratory Protection Standard states that any atmosphere below 19.5% oxygen is dangerous for human health.

Read: Definition of “Oxygen deficient atmosphere”.

If 60% of air is re-breathed/previously exhaled air, consisting of 16% oxygen, and 40% of the air breathed is 21% oxygen, the overall percentage of oxygen in 100% of the air being breathed in while wearing a mask, is 18%. Below the 19.5% OSHA Respiratory Protection Standard.

(2016) https://www.oatext.com/pdf/TEC-1-106.pdf

Use of Surgical Face Masks to Reduce the Incidence of the Common Cold Among Health Care Workers in Japan: A Randomized Controlled Trial.

“Conclusion: Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds.”

Common colds are often caused by coronaviruses.

(2009) https://pubmed.ncbi.nlm.nih.gov/19216002/

From the Center for Infectious Disease Research and Policy at the University of Minnesota:

“Limited, indirect evidence from lab studies suggests that homemade fabric masks may capture large respiratory droplets, but there is no evidence they impede the transmission of aerosols implicated in the spread of COVID-19, according to a paper published yesterday by the National Academy of Sciences, Engineering, and Medicine.

In the paper, the National Academies’ Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats said that, because no studies have been done on the effectiveness of cloth masks in preventing transmission of coronavirus to others, it is impossible to assess their benefits, if any.”

(2020) https://www.cidrap.umn.edu/news-perspective/2020/04/data-do-not-back-cloth-masks-limit-covid-19-experts-say

From the World Health Organization:

“At present, there is no direct evidence (from studies on COVID- 19 and in healthy people in the community) on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID-19.”

(June 2020) https://apps.who.int/iris/rest/bitstreams/1279750/retrieve

Evaluating the efficacy of cloth facemasks in reducing particulate matter exposure:

“our results suggest that cloth masks are only marginally beneficial in protecting individuals from particles<2.5 μm.”

(2017) https://pubmed.ncbi.nlm.nih.gov/27531371/

Simple respiratory protection–evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles.

“…common fabric materials may provide marginal protection against nanoparticles including those in the size ranges of virus-containing particles in exhaled breath.”

(2010) https://www.ncbi.nlm.nih.gov/pubmed/20584862

The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence:

“None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”

(2012) https://www.ncbi.nlm.nih.gov/pubmed/22188875

The Physiological Impact of N95 Masks on Medical Staff:

“Wearing N95 masks results in hypooxygenemia [low oxygen] and hypercapnia [carbon dioxide retention] which reduce working efficiency and the ability to make correct decision.

Medical staff are at increased risk of getting ‘Severe acute respiratory syndrome'(SARS), and wearing N95 masks is highly recommended by experts worldwide. However, dizziness, headache, and short[ness] of breath are commonly experienced by the medical staff wearing N95 masks.”

(2005) https://clinicaltrials.gov/ct2/show/NCT00173017

Reusing masks may increase your risk of coronavirus infection, expert says:

(2020) https://www.news-medical.net/news/20200315/Wearing-masks-may-increase-your-risk-of-coronavirus-infection-expert-says.aspx

Masks-for-all for COVID-19 not based on sound data.

Commentary from Dr. Brosseau, a national expert on respiratory protection and infectious diseases and professor (retired), University of Illinois at Chicago, and Dr. Sietsema, also an expert on respiratory protection and an assistant professor at the University of Illinois at Chicago:

“…we continue to conclude that cloth masks and face coverings are likely to have limited impact on lowering COVID-19 transmission, because they have minimal ability to prevent the emission of small particles, offer limited personal protection with respect to small particle inhalation…”

(2020) https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data

Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial.

N95-masked health-care workers (HCW) were significantly more likely to experience headaches. Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds.

(Colds are caused by coronaviruses.)

(2009) https://www.ncbi.nlm.nih.gov/pubmed/19216002

Face masks to prevent transmission of influenza virus: a systematic review.

There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission. There are fewer data to support the use of masks or respirators to prevent becoming infected.

(2010) https://www.cambridge.org/core/journals/epidemiology-and-infection/article/face-masks-to-prevent-transmission-of-influenza-virus-a-systematic-review/64D368496EBDE0AFCC6639CCC9D8BC05

The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence:

“There were 17 eligible studies… None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”

(2011) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/#idm140166105578400title

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial.

“In this pragmatic, cluster randomized clinical trial involving 2862 health care personnel, there was no significant difference in the incidence of laboratory-confirmed influenza among health care personnel with the use of N95 respirators (8.2%) vs medical masks (7.2%).”

(2017) https://jamanetwork.com/journals/jama/fullarticle/2749214

Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis.

“N95 respirators should not be recommended for general public and nonhigh‐risk medical staff those are not in close contact with influenza patients or suspected patients.”

“The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza.”

“There were no statistically significant differences in preventing laboratory-confirmed influenza, laboratory-confirmed respiratory viral infections, laboratory-confirmed respiratory infection, and influenza-like illness using N95 respirators and surgical masks. Meta-analysis indicated a protective effect of N95 respirators against laboratory-confirmed bacterial colonization (RR = 0.58, 95% CI 0.43-0.78).”

Bacteria are much larger than viruses.

(2020) https://onlinelibrary.wiley.com/doi/epdf/10.1111/jebm.12381