You might be fortunate to live in a part of the country where mask-sightings have become mercifully rare. But a surprising number of Americans, particularly those in urban areas, continue to don masks, and most public-health officials would happily make the rest of us do so again if given half a chance. The pandemic may be officially over, but the reckoning with the response must not be.

The mask zealots’ mantra has long been that masks clearly do some good, while they don’t do any harm. The first part of that contention is unsupported by the best medical research, as I’ve detailed in “Do Masks Work?,” “Masks Still Don’t Work,” and (most recently) “The Mask of Ignorance.” The second part—that masks do no harm—is contradicted by the obvious degradation of human social interaction when people are masked, and it has now been further contradicted by a new German study.

That study highlights how much carbon dioxide mask-wearers are breathing back into their own lungs, essentially poisoning themselves in the process. Rather than breathing in the fresh air of freedom, mask-wearers breathe in the tainted air that should have been expelled from their bodies and released out into the open. The authors of the German study observe that “a significant rise in carbon dioxide occurring while wearing a mask is scientifically proven in many studies.”

It is the magnitude of the rise that is most striking. “Fresh air has around 0.04% CO2,” the authors write, while “masks bear a possible chronic exposure to low level carbon dioxide of 1.41–3.2% CO2 of the inhaled air in reliable human experiments.” So, research suggests that mask-wearers (specifically those who wear masks for more than five minutes at a time) are breathing in 35 to 80 times normal levels of carbon dioxide. To put that into perspective, the authors describe chronic exposure at CO2 levels of 0.3 percent—just 8 times normal levels—as “toxic.”

The German study is a scoping review of existing research, and it aimed “to investigate the toxicological effects of face masks in terms of CO2 rebreathing on developing life, specifically for pregnant women, children, and adolescents.” Breathing in too much carbon dioxide can harm the human body in a wide variety of ways. The potential symptoms mentioned by the authors include “increased heart rate, increased blood pressure and overall increased circulation with the symptoms of headache, fatigue, difficulty concentrating, dizziness, rhinitis, and dry cough,” as well as “respiratory acidosis, metabolic stress, increased blood flow and decreased exercise tolerance.” In addition, they write, “Testes metabolism and cell respiration have been shown to be inhibited increasingly by rising levels of CO2.”

The authors note that pregnant women, obeying mask mandates, have been forced to breathe in levels of CO2 that would be prohibited if they were serving on a Navy submarine. They write that “it is clear that carbon dioxide rebreathing, especially when using N95 masks, is above the 0.8% CO2 limit set by the US Navy to reduce the risk of stillbirths and birth defects on submarines with female personnel who may be pregnant.”

The authors also note the “significant rise of 28% to 33% in stillbirths worldwide and a reduced verbal, motor, and overall cognitive performance of two full standard deviations in scores in children born during the pandemic.” They highlight data from Australia, which show “lockdown restrictions and other measures (including masks that have been mandatory in Australia), in the absence of high rates of COVID-19 disease, were associated with a significant increase in stillborn births.” But “no increased risk of stillbirths was observed in Sweden,” which eschewed the sorts of Covid policies that public-health officials successfully pushed executives (not legislators) to adopt in most developed countries. Such executives foolishly failed to realize that public-health officials love public-health interventions, whether or not they are supported by science.

As for countries that have long worn masks on a somewhat regular basis, the authors write, “Even before the pandemic, in Asia the stillbirth rates have been significantly higher” than in Eurasia, Oceania, or North Africa.

The authors state, “It has to be pointed out that this data on the toxicity of carbon dioxide on reproduction has been known for 60 years.” Thus, they write, the National Institute for Occupational Safety and Health (NIOSH), which is part of the Centers for Disease Control and Prevention (CDC), has CO2 threshold limits of 3 percent for 15 minutes and 0.5 percent for 8 hours in workplace ambient air. Yet the CDC has been relentlessly pushing masks.

The evidence suggests that some damage from breathing in too much CO2 may be irreversible. Among pregnant “mammals who were chronically exposed to 0.3% CO2,” the authors write, “the experimental data demonstrate a teratogenicity with irreversible neuron damage in the offspring.” Nor are these effects limited to the unborn. The authors describe in detail one test of whether excessive CO2 inhalation produces only “a short-term effect or possible substantial damage to brain function”:

[A] study in mice was performed and published…. Adolescent mice were exposed 24 [hours] a day for 7 weeks to a level of 0.3% carbon dioxide…. At the end of the study a so-called water maze exercise was performed. Here the mice have to find a life-saving platform in a water basin. This test distinguishes between impact on physical function and on mental function…. On the first test day mice in all groups (carbon dioxide exposed and normal air exposed) typically needed around 40 [seconds] to find the platform. Healthy mice exposed to normal air learned to find the platform more quickly and after four days the healthy mice finally only needed 20 [seconds] to find the platform, whereas the carbon dioxide exposed mice were unable to learn the shortest way to the platform. Although the carbon dioxide exposed mice were able to swim as quickly as their healthy controls, they were not able to learn the shortest route. They swam around in a very disoriented manner….Histology tests demonstrated apoptosis of brainstem neurons [in the CO2-exposed mice]…. This CO2-induced loss of neurons is irreversible.

All other things being equal, the people most likely to experience the ill-effects of breathing in too much carbon dioxide are those who wear masks for the longest periods of time, and those who wear N-95 masks. In other words, the people most likely to suffer from excessive CO2 inhalation are the mask zealots—and, sadly, their children.

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Given that the same forces that want to mandate masks with no scientific evidence want to transform our economy with little to no scientific evidence, the authors aptly conclude, “Instead of only worrying about the potential risks of a future harmful long-term CO2 increase in the atmosphere with impact on human health…the focus of research should also be on the current mask-related CO2 increase in breathing air.”

Of course, there are other big problems with masks, beyond their causing one to breathe back in one’s own carbon dioxide. As I said on Tucker Carlson Tonight when discussing “The Masking of America” in the summer of 2021, “A country that forgets the importance of the face is probably also going to forget the importance of certain unalienable rights. When we walk around looking like faceless stormtroopers, it doesn’t exactly inspire a lot of confidence that we are fit to be free, self-governing citizens in a republic.”

When governing authorities choose to depart from centuries of Western norms, imposing a radical new course of action upon huge swaths of the citizenry, they better make sure they have extremely compelling evidence for doing so. In the case of the mask regime, there was no compelling evidence to support the decrees. Masks are uncomfortable, unhygienic, and ineffective. They undermine human social interaction. And it is now increasingly clear that they are bad for your health.