A man and carbon dioxide

Carbon dioxide is an important metabolic link. The total amount of carbon dioxide in various forms inside a person is 100 — 120 liters, which is approximately 70 times more oxygen reserves in blood and tissues. CO₂ has a direct effect on the central nervous system, as it is involved in the regulation of respiration. The most critical element of the respiratory function is not the flow of oxygen, but the removal of carbon dioxide from the body.

For a long time, no one knew about the effects of CO₂ on health. But with the beginning of the rapid development of technology in the 19th century, people working with sources of increased emission of carbon dioxide (furnaces of steam boilers, smelting furnaces, coke oven batteries, etc.) or in conditions of its excessive accumulation (underground and underwater work), experienced its acute effect, leading to poor health, headaches, decreased performance, inflammation of the nasopharynx, bronchi and lungs. Such a condition, called hypercapnia — an excessive accumulation of carbon dioxide in the human body, with prolonged exposure could lead not only to disability, but also to death, due to the development of respiratory acidosis — blood acidification by the resulting carbonic acid. The higher the concentration of CO₂ in the air, the greater the concentration of carbonic acid. The amount of carbon dioxide in the air is estimated by volumetric content in percent (vol.%) Or parts per million — ppm (part per million).

For the first time, the German hygienist Max Pettenkofer suggested using the value of the concentration of carbon dioxide as a criterion for the suitability of air for human breathing. He wrote scientific papers on air exchange in residential buildings and evaluated building materials and fabrics for the production of clothing in terms of their breathability. However, for a long time it was not possible to establish a level of CO₂ content in the air of working rooms that is safe for humans. It turned out that under extreme conditions, for example, on submarines, a person for several weeks can withstand the presence of up to 15,000 … 20,000 ppm (1.5 … 2 vol.%) оf CO₂ in the air. However, at such a concentration, acidosis arose, which was compensated by the body’s homeostasis system due to the internal reserves of buffer chemicals. At workplaces in premises in which people spend 8 hours for 5 days a week for 40 … 50 years, such concentrations of course were unacceptable, therefore, the norm was set at 5000 ppm (0.5 vol.%), Which guaranteed with the specified duration of exposure, the absence of acidosis with moderate hypercapnia, which is within the physiological endurance of a person.

In 1964, using the electroencephalography method, it was found that even short-term inhalation of air with a CO₂ concentration of 1000 to 5000 ppm (0.1 to 0.5 vol.%) Causes noticeable changes in the respiratory system, blood circulation and electrical activity of the brain. Therefore, in most regulatory documents, 1000 ppm was taken as the permissible content of carbon dioxide in the air of working premises. However, it is obvious that for residential premises, in which a person spends much more time, and can spend his whole life, the CO₂ content should be much lower. For around-the-clock exposure for 80 years, a value of 500 ppm (0.05 vol.%) has been recommended. How are things today?

Currently, there has been a tendency towards an increase in the content of CO₂ in indoor air. This is due to the desire of designers to underestimate the performance of ventilation systems in the premises in order to save energy spent on heating buildings in the cold season or cooling the air in the hot season. Therefore, even with properly designed and efficient ventilation, in the premises of a building located in the center of a large city, the concentration of CO₂ in high quality air will not be lower than 800 ppm, and in the air of acceptable quality — 1400 ppm.

However, the ventilation system may not provide acceptable air quality in the building due to an increase in the number of people in the room, replacement of window frames with double-glazed windows, clogging or blocking of air ducts, etc. The lack of requirements for monitoring the carbon dioxide content during the operation of buildings and structures leads to an unacceptable deterioration in the state of the air environment. The concentration of CO₂ in some industrial premises at the end of the working day with faulty ventilation can reach 2500 ppm, in residential apartments with double-glazed windows after a night’s sleep — 2000 ppm, in educational institutions by the end of classes — 1500 ppm, in kindergartens — 700 ppm.

In light of the COVID-19 problem, these data allow us to see another reason for the extremely severe course of the disease and even death. Max Pettenkofer, for example, believed that the role of external factors such as the quality of air, water and food in the onset and course of disease is much more important than the role of the pathogens themselves. On this occasion, he discussed with Robert Koch, who discovered Vibrio cholerae in 1883. In 1892, at the age of 73, Pettenkofer even publicly drank cholera culture on a bet. He wanted to prove that without a number of concomitant factors, the disease will not develop. Pettenkofer did not really get sick, but, as it turned out, 40 years ago he had already suffered mild cholera. Therefore, we can say that in the dispute between Max Pettenkofer and Robert Koch he won… Ilya Mechnikov is the creator of the theory of immunity.

Increased levels of CO₂ in the inhaled air can disrupt the functioning of the human immune system. It was found that when a person was exposed to CO₂ in the concentration range from 1000 to 4000 ppm for 2 hours, human immune cells — neutrophils increased the production of microvesicles (vesicles) with a high content of interleukin IL-1β. This interleukin belongs to cytokines (small peptide molecules) that can activate inflammation. Actually, the rapid growth of the «cytokine storm» is the main cause of severe complications and mortality in coronavirus infection. Therefore, the requirement for self-isolation of carriers of coronavirus, that is, forcing them under the threat of fines to spend continuously long (up to 2 weeks) time in confined spaces with the possible high accumulation of CO₂ in the air, to some extent contradicts modern scientific data and contributes to the severe course of the disease and the development complications.

Since the quality of the indoor environment can play a significant role in the severity of coronavirus infection, the standards for ventilation of buildings are currently being revised. The main recommendation is to supply as much outside air as possible. The key aspect is the amount of fresh air supplied per person. Air conditioning (humidification, cooling) has no practical effect. In buildings without mechanical ventilation systems, it is recommended to actively use ventilation (much more than usual, even when it causes some thermal discomfort). this is the only way to increase air exchange. In addition, in mechanically ventilated buildings, opening windows can be used to further increase air exchange.

How can the air quality be monitored to make sure that the room is sufficiently ventilated and what causes frequent inflammatory diseases of the respiratory tract and lungs — bacteria and viruses, or an unfavorable microclimate, or high CO₂ content?

The problem of poor air quality, for example, in schools arises from the accumulation of CO₂ after the installation of double-glazed windows or poorly carried out repairs that impair ventilation. The main way to eliminate the harmful effects of indoor air in such conditions is ventilation. Therefore, it is extremely important to provide the necessary ventilation of the room, which would normalize the carbon dioxide content. Measurements of the content of carbon dioxide in the breathing zone showed that the concentration of CO₂ increases rapidly after a person has taken a seat and started to work, since an individual «bubble» of air is formed around him, in which carbon dioxide accumulates. Personal ventilation is offered to prevent its occurrence.

However, at present, there is a tendency to increase the concentration of CO₂ in the atmospheric air as a whole, which can make ventilation an ineffective way to provide the chemical composition of indoor air that is necessary for a person. If staying in the fresh air is a means of preventing the harmful effects of polluted indoor air, then with a further increase in the concentration of carbon dioxide in the atmosphere, this technique will no longer work. The problem of chronic exposure to CO₂ will arise.

With the accumulation of carbon dioxide in the body, such a pathogenic biomineral as calcite (calcium carbonate) is formed. One of the sources of carbonate ions [CO₃^2-] is carbonic acid, which is formed when CO₂ dissolves in the blood and decomposes with the formation of bicarbonate [HCO₃^—] which ultimately leads to the formation of carbonates. Following an increase in the concentration of carbonic acid, the concentration of carbonate will increase. When the product of the concentrations of calcium ions and carbonate ions exceeds the product of solubility, the calcification process begins, i.e. the formation of calcium carbonate. Thus, a pump is formed for pumping calcium from bones into the formation of pathogenic minerals with a decrease in the value of blood acidity. The growth of pathogenic biominerals can lead to the destruction of bones due to the loss of calcium.

To prevent these processes from becoming widespread, it is necessary to introduce the maximum permissible concentration (MPC) of CO₂ in the atmosphere. Irreversibility of pathogenic processes will go everywhere on the planet, if the maximum permissible concentration for CO₂ in the atmosphere is exceeded, because nowhere will the process of restoring the human body be ensured.

There are different points of view on this issue.

1. Humanity has no impact on the biosphere. Volcanoes emit more CO₂ than the technosphere.

2. The concentration of CO₂ in the atmosphere is growing due to the influence of humans and the technosphere. But this has no effect on the climate. A person will be able to live normally at very high concentrations of carbon dioxide.

3. Man and the technosphere affect the ecological environment on the planet, as a result of which the concentration of carbon dioxide in the atmosphere increases and global warming occurs. But all these changes are beneficial! Humanity has prevented another ice age, and carbon dioxide is good for plants.

In fact, for a person who knows ecology, it is clear that «nothing comes for free.» And the «abolition of the ice age» is by no means an achievement to be proud of, but a gross interference in natural processes. And the result is not an improvement in the weather outside the window, but an increase in dangerous natural phenomena, both meteorological (squalls, storms, hurricanes, tornadoes, etc.) and hydrological, caused by an increase in precipitation (flooding, floods, destruction of dams, bridges, residential buildings, etc.).

As for the benefits of CO₂ for humans, and not only for plants, we are reassured by anesthesiologists and resuscitators: «The addition of CO₂ not only does not worsen, but even improves the parameters of lung ventilation, blood oxygen saturation and blood supply to the brain.» Yes, indeed, due to the fact that carbon dioxide has a direct direct effect on the respiratory function, with its excess in the blood, the respiratory center of the brain is stimulated. The ventilation of the lungs is enhanced and the blood supply to the whole organism, including the brain, is improved.

But this is a highly specialized point of view. For how long should the respiratory center be stimulated by introducing excess CO₂ into the lungs? At the time of resuscitation, that is, 20-30 minutes. Even if for the entire duration of a long operation, it is still 5-6 hours. With CO₂ concentrations above 1000 ppm, even short-term inhalation of air will cause problems. Moreover, the problems are created by prolonged, throughout life, exposure to slightly increased concentrations of carbon dioxide. Man, as a biological species, was formed under conditions when the concentration of CO₂ in the air never exceeded 310 ppm but did not decrease to less than 180 ppm, as was established on the basis of studies of air bubbles frozen in the ice of Antarctica for more than 400 thousand years.

An Intergovernmental Panel on Climate Change (IPCC), operating at the UN proposed four scenarios for a further increase in the concentration of CO₂ in the Earth’s atmosphere, depending on the further actions of the world society. According to the most optimistic scenario, the CO₂ concentration in the Earth’s atmosphere will reach 450 ppm by 2060 and decrease to 421 ppm by 2100. The most pessimistic forecast assumes an increase in carbon dioxide content to 936 ppm in 2100, after which the increase in CO₂ concentration in the atmosphere will continue at the same rate. However, due to the fact that the priority attention is now given to changes in the global climate, the problem of the direct and immediate impact of an increase in carbon dioxide in the atmosphere on health remains underestimated.

Population medical studies of the US population showed an increase in the amount of bicarbonates in the blood serum from 23.7 mmol / L in 2000 to 25.2 mmol / L in 2012, which indicates compensation for mild forms of mass acidosis. In addition to the previously established fact that acidosis compensation leads to multiple organ damage to the human body caused by calcification deposits, other long-term health effects of elevated carbon dioxide levels have recently been identified. In studies of scientists, data are given that even a small increase in the concentration of CO₂ in the inhaled air with prolonged exposure to humans, even small compared to the threshold for acute exposure (1000 ppm), can cause endocrine disorders of the thyroid gland function associated with a decrease in the content of free calcium in the blood, which entails followed by pathologies of intrauterine development of the fetus, leading to miscarriages during pregnancy and the birth of dead children.

These health disorders can negatively affect the entire population of Homo sapiens, so that a further increase in the concentration of CO₂ in the Earth’s atmosphere can call into question the survival of humanity in the future. As a result of the problems described above, according to P. Ole Fanger, a building air conditioning specialist, about 5,000 people die every day from poor air quality.

Tkachenko Yu.L., Moscow.

Goshka L.L., Syktyvkar.

Translated by Snezhana Gubaidulina.