Unsupported: There is no evidence showing that breathing in bacteria that one has exhaled can cause an infection.
FULL CLAIM: Wearing a face mask caused a 19-year-old grocery store worker to be hospitalized for a lung infection, due to breathing in her own carbon dioxide and bacteria.
A claim that a healthy 19-year-old grocery store worker was hospitalized for pleurisy, an inflammation of the tissue surrounding the lungs, due to her breathing in carbon dioxide and “her own bacteria” as a result of wearing a face mask, went viral on Facebook at the end of May 2020. Within just a few days after some of the earliest posts, dated 28 May 2020, more than 400 posts containing this claim have appeared on Facebook, with more than 31,000 interactions.
In an early version of the post, the supposed parent of the hospitalized 19-year-old asks others to spread the news of the incident because s/he can’t post publicly, for undisclosed reasons, but that “I know I can trust you not to post with my name”. Health Feedback was unable to find any news reports corresponding to such an incident. It is also not clear why the author remains anonymous if the message is true, as this would be significant to medical experts. Furthermore, there are no names, dates, or independent sources corroborating the incident attached to the message, placing the authenticity of the account in question.
There are also several anomalies in the way the message has been amplified on Facebook. The message has been shared by hundreds of Facebook users who are apparently unrelated to one another. Many of the users claim to be sharing the message on behalf of a friend, which gives the impression that they all somehow know the victim personally. This would mean that the anonymous person who reported the incident has a personal relationship to hundreds of these users on Facebook, something that is extremely unlikely to happen.
Some versions of the message do include a name—we have seen at least four different ones so far—attached either at the beginning or end of the post, as if the story came from a specific person. It is extremely unlikely that four different people had the exact same experience and wrote identical messages about it, complete with the same typographical errors. Some versions of the message also hint at the location of the incident, but this has varied widely and has included different states such as California and Alabama. Taken together, these features of the posts suggest that the message is not authentic and that its spread is potentially coordinated by a group, perhaps with the intent of spreading misinformation about face masks.
The claim that wearing a mask can cause illness from breathing in one’s own carbon dioxide and bacteria bears strong resemblance to earlier viral claims. Most notably, an article by former neurosurgeon Russell Blaylock claimed 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”, and that wearing a face mask leads to an accumulation of carbon dioxide in the blood (hypercapnia). Health Feedback addressed both claims in an earlier review and found them to be unsupported.
Firstly, the claim that rebreathing one’s own exhaled air, which might contain viruses and bacteria, can cause infection is unsupported and illogical. While it is true that pleurisy can be caused by microbial infections, in addition to trauma, cancer, autoimmune disease, certain medications, and other causes, there is no evidence to suggest that the condition could be caused by wearing a face mask. If someone is exhaling viruses and bacteria, 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 microorganisms that they previously exhaled.
Secondly, face mask filters are large enough to allow gas molecules such as carbon dioxide and oxygen to pass through freely. We can observe this in healthcare workers who wear masks for long periods of time yet do not demonstrate significant impairment in work performance, as would be the case if masks caused hypercapnia. Using a face mask is not known to lead to hypercapnia in healthy people, as explained by Health Feedback in this review.
The general public has been advised not to use surgical face masks or N95 masks, as these are in limited supply and should be reserved for healthcare professionals. Instead, the U.S. Centers for Disease Control and Prevention have recommended that the general public use cloth face coverings. Although these do not provide the same level of protection as N95 masks, they are still able to reduce exposure to potentially infectious droplets produced by talking, coughing, or sneezing. In fact, respiratory droplets have been identified as the main mode of COVID-19 transmission. Such droplets, which are more than 5 to 10 micrometers in size, are much larger than the virus itself; SARS-CoV-2, the causative agent for COVID-19, is about 60 to 140 nanometers, at least 70 times smaller than droplets. The size of a carbon dioxide molecule is even smaller, estimated at around 230 picometers, about 260 to 600 times smaller than the virus.
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.
Studies have shown that even simple face coverings can reduce exposure to respiratory droplets. A study published in the New England Journal of Medicine found that wearing a wet washcloth greatly reduces exposure to speech droplets in the air. Another study in ACS Nano observed that well-fitted face masks made of common materials including cotton can filter out between 80 to 99% of droplets, depending on droplet size. Finally, 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.
However, prolonged face mask use should be exercised with caution by people with pre-existing respiratory issues. The same caution also applies to cloth face coverings; the U.S. Centers for Disease Control and Prevention 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.”
Given that the message makes sensational claims that are unsupported by scientific evidence and that no independent sources can be found to support the anonymous report, the veracity of the claim is dubious at best.
We previously stated that “The size of a carbon dioxide molecule is even smaller, estimated at around 230 picometers, about 10,000 times smaller than the virus.” This is incorrect. It should state that the size of a carbon dioxide molecule is about 260 to 600 times smaller.
- 1 – Zhu et al. (2020) A Novel Coronavirus from Patients with Pneumonia in China, 2019. New England Journal of Medicine.
- 2 – He et al. (2020) Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature Medicine.
- 3 – Anfinrud et al. (2020) Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering. New England Journal of Medicine.
- 4 – Konda et al (2020) Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano.