Incorrect: Claims that wearing a face mask causes “accumulation of carbon dioxide” is contradicted by the fact that face mask filters are large enough to allow gas molecules such as carbon dioxide and oxygen to pass through freely. Healthcare workers who wear masks for long periods of time do not demonstrate significant impairment in work performance, as would be the case if masks caused hypercapnia.
FULL CLAIM: "New evidence shows wearing face mask can help coronavirus enter the brain and pose more health risk, warn expert"
This article reports claims made by Russell Blaylock, a former neurosurgeon who has promoted scientifically unsupported views on subjects including vaccines and more recently, COVID-19. These claims were originally published in another article, in which Blaylock claimed that face masks can cause people to inhale their own “exhaled virus” which then travels to the brain, and that face masks can cause hypoxia (low oxygen) and hypercapnia (elevated CO2). Published on 18 May 2020, the Science Times article went viral in a day and has been viewed more than one million times on Facebook.
To support the claim that face masks pose “a serious health risk for wearers”, the article cited “a study conducted by the National Taiwan University Hospital”. However, the provided link directs readers to registration details of a clinical trial, which contains no results from the study that ended in 2005 and for which no results appear to have been reported or published. In addition, the study examined the health effects of wearing N95 masks on medical personnel and not the cloth face masks that non-medical personnel are encouraged to wear in public.
The article also cited another study conducted in Singapore, in which healthcare workers completed a self-administered questionnaire asking whether they experienced headaches while using N95 masks. The study reported that having a previous history of headaches and using N95 face masks for longer than four hours was associated with headaches. However, the study’s authors also highlighted that they did not include any control groups, nor did they evaluate other potential factors that may predispose healthcare workers to headaches, such as stress and lack of sleep. In short, the study did not find a causal association between N95 mask use and headaches. In fact, the authors stated that “The N95 face-mask is generally well tolerated, with minimal adverse effects.”
The article further claims that there is “new evidence” showing that using a face mask enables the virus to enter the brain, but it fails to actually cite any. It is true that COVID-19 can affect the brain and the rest of the central nervous system, both directly and indirectly, and that some COVID-19 patients exhibit neurological symptoms, among many other symptoms, which was reported in this Science news article. However, researchers are still trying to understand the causes of these symptoms and as yet there is no scientific evidence indicating that the use of face masks is related to the neurological symptoms in COVID-19 patients, nor does existing evidence suggest that it is likely that masks would have such an effect.
Blaylock’s claim that “By wearing a mask, the exhaled viruses will not be able to escape and will concentrate in the nasal passages, enter the olfactory nerves, and travel into the brain”, is unsupported and illogical. If someone is exhaling the virus, then they are already infected. The spread of the infection would be largely determined by how well the person’s immune system fights off the infection, not by whether they inhaled virus particles that they previously exhaled.
It should be noted that the claims of hypoxia, hypercapnia, and increased risk of brain infection from SARS-CoV-2 deal primarily with N95 masks, which are named for their ability to filter out at least 95% of airborne particles, including viruses. Cloth face coverings do not provide the same level of protection as N95 masks but are recommended by the U.S. Centers for Disease Control and Prevention (CDC) for use by the general public due to their ability to at least reduce exposure to potentially infectious droplets produced by talking, coughing, or sneezing. Respiratory droplets have been identified as the main mode of COVID-19 transmission.
Droplets from speech have been shown to stay in the air between eight to 14 minutes. Infectious droplets can also be generated by people who are asymptomatic or pre-symptomatic, that is, not showing any sign or symptom of disease. As such, wearing a cloth face covering helps prevent asymptomatic and pre-symptomatic carriers from transmitting the infection to others. Jeremy Howard, a research scientist at the University of San Francisco, and other scientists have compiled a list of research publications supporting the use of face coverings for reducing disease transmission.
Contrary to another of Blaylock’s claims, using a face mask is not known to lead to hypercapnia or hypoxia in healthy people, as explained by Health Feedback in this review, although prolonged use should be exercised with caution by those with pre-existing respiratory issues. The same caution should also be applied to cloth face coverings; the CDC has indicated that “Cloth face coverings should not be placed on young children under age 2, anyone who has trouble breathing, or is unconscious, incapacitated, or otherwise unable to remove the mask without assistance.”
Health authorities and experts acknowledge that face masks and cloth face coverings do not provide 100% protection from infection, but they play an important role in reducing the risk of disease transmission. This is analogous to seat belts, which also do not prevent 100% of all deaths and injuries during a traffic accident, but still play a significant role in reducing the risk of such outcomes. The article’s implication that safety interventions are not helpful if they do not produce perfect results is an example of the nirvana fallacy, in which a realistic solution to a problem is dismissed simply because it does not achieve an impossible ideal.
- 1 – Lim et al (2006) Headaches and the N95 face-mask amongst healthcare providers. Acta Neurologica Scandinavica.
- 2 – Baig AM. (2020) Neurological manifestations in COVID‐19 caused by SARS‐CoV‐2. CNS Neuroscience and Therapeutics.
- 3 – Stadnytskyi et al. (2020) The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission. PNAS.
- 4 – He et al. (2020) Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature Medicine.