VERA FILES FACT CHECK: Prolonged mask use DOES NOT cause hypoxia

A false warning is circulating online that claims wearing face masks for long periods of time causes hypoxia, a health condition where the body’s tissues do not get enough oxygen.

“The use of face masks does not cause hypoxia nor excessive intake of carbon dioxide. Masks are designed to allow proper breathing and oxygenation,” the World Health Organization (WHO) Philippines told VERA Files in an email.

Published as a status update and reproduced in screengrabs by several netizens on Facebook (FB) on May 14, the post argued that breathing in the carbon dioxide exhaled by a person using the mask causes dizziness and “intoxication.”

This claim has similarly been debunked by fact checkers across five continents, making the rounds in at least 12 countries as early as April 30.

Agence France-Presse, in an interview with Dr. Emilio Herrera, a professor of pathophysiology and expert in hypoxia at the University of Chile, said face masks “cannot generate hypoxia.”

“For that, the mask would have to be hermetically glued to our skin,” Herrera said in Spanish.

A fact check by Reuters also says that for the general public, who mostly wear face coverings in short stints during social distancing, it is unlikely for them to suffer extreme complications while wearing a mask.

The United States (U.S.) Centers for Disease Control and Prevention (CDC) told Reuters: “The CO2 will slowly build up in the mask over time. However, the level of CO2 likely to build up in the mask is mostly tolerable to people exposed to it. You might get a headache but you most likely [would] not suffer the symptoms observed at much higher levels of CO2.”

Australia-based epidemiologist Dr. Abrar Ahmad Chughtai of the University of New South Wales also told Snopes that hypoxia is unlikely to take place with cloth and surgical masks because they are not tight-fitting.

Chughtai, however, did point out that those with pre-existing respiratory conditions such as asthma or chronic obstructive pulmonary disease “may face difficulty breathing” when using some types of tight-fitting masks like respirators.

The false posts also claimed that “people who serve the public for eight hours” are being counterproductive because they are “intoxicating themselves without knowing it.”

A study in 2013 recorded in the U.S. National Library of Medicine website involving 10 nurses who wore N95 masks during two full 12-hour shifts, showed evidence disputing the claim. While it recorded “perceived exertion, perceived shortness of air, and complaints of headache and lightheadedness,” it concluded there were no “clinically relevant” physiological changes caused by long-term use of respirators.

Though there was a rise in carbon dioxide levels, it did not result in an increase “that reached the clinical definition of hypercapnia,” or having too much carbon dioxide in the blood, the study added.

WHO Philippines also told VERA Files that “there is no evidence to show that prolonged use of face masks causes adverse effects on the brain or heart functioning.”

The inaccurate post also made a recommendation: to lift one’s mask every 10 minutes “to continue feeling healthy.”

This can be problematic because as the U.S. CDC warns, the most significant risk of extended use and reuse of respirators is of “contact transmission from touching the surface of the contaminated respirator.”

WHO says to “clean your hands with alcohol-based hand rub or soap and water” every time one touches the mask. It also advised to replace a mask as soon as it is damp, and to not reuse single-use masks. Cloth masks, on the other hand, must be washed routinely, according to the U.S. CDC.

Several versions of the false post circulating in the Philippines features a screengrab of a May 15 FB status by a Barbuda-based netizen which has been shared nearly a thousand times. The exact same text in the status update, however, could be found on public FB groups and pages as early as May 1, the earliest of which is from a Spanish version of the text accompanied by an English translation.

(Editor's Note: VERA Files has partnered with Facebook to fight the spread of disinformation. Find out more about this partnership and our methodology.)

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