Face masks do not cause hypercapnia or blood acidity; there is no evidence that these conditions increase the risk of cancer


Face masks cause hypercapnia and blood acidity, which could increase cancer risk


Incorrect: Face masks cannot block gas exchange because the gas molecules are much smaller than the pores of the face mask. Therefore, face masks are extremely unlikely to cause a significant increase in blood carbon dioxide levels.
Flawed reasoning: The claim that the acidity induced by the face mask facilitates the development of cancer has no scientific basis. There is no evidence that face masks cause hypercapnia in the first place, or that body acidity triggers cancer, which is caused by mutations.


Face masks act as a physical barrier that blocks infectious respiratory droplets. However, the pores in the mask are still large enough to allow the passage of tiny gas molecules, including carbon dioxide. Therefore, wearing a face mask cannot cause carbon dioxide to build up in amounts large enough to cause blood acidity. Moreover, cancer is caused by mutations and not by body acidity.

COMPLETE CLAIM: “And then we are going to hide our children, knowing that if they have cancer it will be very permissive and a return of cancer?” Knowing that it can be permissive to have cancer? »


A video featuring molecular biologist Christina Parks circulated on video and social media platforms (examples here and here) in October and November 2022. In this video, Parks claimed that face masks cause carbon dioxide buildup in the blood which makes it acidic. She added that this acidic environment could be “license to get cancer”.

Parks’ speech was originally posted on America’s Frontline Doctors website on September 6, 2022, where it has been viewed over 3,400 times. The group then shared the video on Twitterreceiving over 7,000 interactions and 4,600 retweets.

America’s Frontline Doctors organization is well known for spreading misinformation about COVID-19 vaccines and promoting unproven COVID-19 treatments. This behavior led the U.S. House Select coronavirus subcommittee to launch an investigation into the group in October 2021. Parks has also been criticized for spreading misinformation about COVID-19 and COVID-19 vaccines before the House. Michigan Legislature when she testified in support of a bill (HB4471) that would ban employers from mandating vaccines in the workplace.

Parks based his claim about face masks and cancer on two arguments. The first is that face masks raise the level of carbon dioxide in the blood to the point where it becomes acidic. The second is that an acidic environment increases the risk of developing cancer. But as this review will explain, there is no scientific evidence to support either claim.

Face masks allow gas exchange because the gas molecules are smaller than the pores of the mask materials

Carbon dioxide is a gas that the body produces as waste when it burns food for energy. In a healthy body, carbon dioxide is transported through the bloodstream to the lungs and is eliminated through respiration. However, certain medical conditions can alter the balance between carbon dioxide production and elimination. This can cause carbon dioxide to build up in the body to harmful levels. When these levels exceed a certain threshold, the condition is called hypercapnia.

Symptoms of hypercapnia vary in severity, ranging from mild headaches, flushed skin, drowsiness and dizziness to confusion, irregular heartbeats, unconsciousness and even death.

Any condition that reduces a person’s ability to remove carbon dioxide from the bloodstream can lead to hypercapnia due to respiratory failure. Examples of such conditions include chronic obstructive pulmonary disease and asthma, lung and spinal cord injury, and conditions affecting the respiratory muscles or regions of the brain that control breathing. Additionally, metabolic conditions such as thyroid disease, neuromuscular disorders, and overdose of sedatives can also cause hypercapnia.

Face masks act as a physical barrier that reduces the emission and breathing of infectious respiratory droplets[1], which are larger than the pores of face mask materials. But as Health Feedback explained in a previous review, the gas molecules are much smaller than the mask’s pores, allowing them to pass through.

Because face masks cannot block gas exchange, they are extremely unlikely to cause significant changes in blood carbon dioxide levels. As Sofia Morra, a cardiologist at Erasme University Hospital in Brussels, explained to Health Feedback in a previous review:

“Wearing a surgical mask for short periods does not significantly impact physiological respiratory variables[2] and so, whenever an increase in CO2 occurs in the “dead space” of the mask, the magnitude of that increase is unlikely to be sufficient to alter immune, neurological, or cardiovascular homeostasis.

As noted by the American Lung Association and the Mayo Clinic, empirical evidence from healthcare workers also contradicts the claim that face masks cause hypercapnia. The two organizations explained that healthcare workers have worn face masks for long periods of time for decades without any evidence of adverse health reactions or negative impact on their work performance.[2].

Studies specifically assessing the impact of face masks on blood carbon dioxide levels further support the safety of face masks. For example, two studies conducted in Canada and the United States reported that face masks had no impact on blood oxygen and carbon dioxide levels in the elderly, healthy, and elderly. patients with chronic obstructive pulmonary disease, who are at increased risk for carbon dioxide. retention[3,4].

Another study conducted by researchers in Italy, evaluated the effect of surgical masks and N95 on different respiratory parameters in children during rest and physical activity.[5]. The researchers observed no significant effect of the surgical masks. While the use of N95 masks increased arterial blood carbon dioxide levels, particularly during physical activity, concentrations remained within a normal range. None of the children who participated in the study showed signs of respiratory distress.

In short, wearing a face mask can cause discomfort and minimal changes in oxygen and carbon dioxide levels. However, it is extremely unlikely to cause a significant increase in carbon dioxide to the point of causing hypercapnia.

There is no evidence that body acidity can trigger cancer or increase the risk of developing it

Park correctly stated that a potential complication of hypercapnia is respiratory acidosis. This condition results from the buildup of carbon dioxide in the blood to such an extent that it alters its acid and base balance, making it too acidic. The kidneys can often compensate for slow changes in blood acidity by regulating the flow of bicarbonate. However, when acidosis is very severe or occurs suddenly, the kidneys cannot compensate for it. In this case, acidosis can damage the organs.

That said, there is no scientific evidence linking respiratory acidosis to cancer. As Health Feedback has explained in previous reviews, cancer is caused by mutations, not the acidity of the body. These mutations can arise due to multiple factors, including random errors during cell division and environmental factors that damage DNA. Additionally, some inherited mutations can also increase a person’s likelihood of developing cancer.

Many claims linking body acidity and cancer stem from a misinterpretation of the Warburg effect[6], a phenomenon described by chemist and physician Otto Warburg. Warburg discovered that while healthy cells preferentially produce energy using oxygen, cancer cells tend to obtain energy from the fermentation of glucose, even in the presence of oxygen.

Glucose fermentation produces lactic acid as a by-product, which makes the tumor environment more acidic. This acidic environment is a hallmark of cancer progression[7] and in some cases may promote cancer growth[8,9]. But as Health Feedback previously explained, acidity is likely a consequence of cancer, not its cause.[6]and cancer cells can also grow in an alkaline environment[8,9].

Parks further asserted without any evidence that “we have already seen staggering increases in cancer rates in our children”. According to the American Cancer Society, childhood cancer rates have increased slightly over the past few decades. However, U.S. data on childhood and adolescent cancer rates is only available for 2019 and earlier. Therefore, we cannot reliably compare childhood cancer rates from recent years with data from previous years. And even if if there has been an increase, it could be due to many factors other than the use of face masks, such as improved diagnosis of cancer.

In summary, Park’s claim that “when the body becomes chronically acidic, it is permissive for cancer” is not supported by any scientific evidence. Additionally, there is no evidence that face masks cause hypercapnia in the first place. In fact, available data shows that face masks do not cause significant changes in blood carbon dioxide levels. There is also no evidence to suggest that body acidity increases cancer risk. Therefore, the claim that acidosis resulting from mask-induced hypercapnia increases cancer risk is completely baseless.


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