Role of CO2 on human health and its impact

Carbon dioxide (CO2) is naturally present in the atmosphere in concentrations ranging from 0.03 to 0.06 %. But like all other pollutants in the atmosphere, the anthropogenic sources of CO2 are higher than the natural sources. CO2 is generally used in industries like agro production industries for cooling, conserving, and medical applications. The average ambient concentration of CO2 in fresh air has been rapidly increasing and is currently around 410 ppm (Schmidt 2020). This increase is due to anthropogenic activities, largely due to burning of fossil fuels. CO2 is odorless, colorless, and are heavier than gases in the air (Shusterman and Balmes, 1997). There has been seen an increase in the atmospheric concentration of CO2 in past decades that results in
climate change and adversely affects the health of the living organism. The effect of CO2 on human health had been documented for a long but the safe level for breathing is still not clear. Some reports suggest that permanent exposure to CO2 levels will have a significant effect on human health. In the body, CO2 is synthesized and its partial pressure under the healthy condition in pulmonary capillary blood is greater than that in alveolar air. The harmful effects of CO2 are visible very often in blood PH, lungs, heart, and central nervous system because it can diffuse freely through tissue membranes. The average indoor concentration of CO2 is 0.08% to 0.1% (Guais et al., 2011). Humans and animals have mechanisms that support tolerance to an increased level of CO2 for the short term. But these mechanisms may have severe consequences in a high level of CO2. Concentration above 600 ppm for short-term exposure in indoor environments has shown unhealthy CO2 concentrations in blood (Bierwirth et al., 2018). The harmful effects of CO2 cause acute and chronic diseases to the human body.

CO2 in Indoor environment

CO2 in an outdoor environment and its impact on human health has been widely reported. However, the indoor level of CO2 and its impact on human health is equally concerned. The indoor air quality may not be fatal but it requires some immediate actions. In indoor environments, CO2 concentration is often elevated relative to ambient outdoor levels due to the fact that the exhaled breath from humans contains almost 4% high Carbon dioxide and ventilation may not be adequate to prevent the resulting increase in CO2 (Bierwirth et al., 2018). According to a report published in the Guardian, most researchers these days is suggesting that levels of CO2 that can be found in bedrooms, classrooms, and offices might have harmful effects on the body, including affecting cognitive performance.


Health effects of CO2

Short term effects

High-level exposure to CO2 for short time can cause unconsciousness, cyanosis, sluggish reflexes, rattling respiration, and excessive motor unrest. When O2 is displaced by CO2 it causes a different level of hypoxia along with hypercapnia (Risa, 2014). The effects of CO2 on the metabolism have not been explored much however sensitivity of anaerobic glycolysis in a tumor to the concentration of CO2 bicarbonate buffer system has been reported because of the
metabolic effects of carbon dioxide (Warburg, 1924). Inhalation of CO2 above 5% for 1 hour can lead to pulmonary inflammation. CO2 is an asphyxiant and can lead to unconsciousness if exposed to 30% for 1 min or 10% for 5 to 10 min. 1% of CO2 can immediately affect respiratory function and may result in hypercapnia (Guais et al., 2011).


Long term effects


Table 1 – Potentially Adverse Outcomes of Prolonged Low-Level CO2 Exposure

Source – Rice, S. A. (2014). Human health risk assessment of CO2: survivors of acute high-level
exposure and populations sensitive to prolonged low-level exposure. environments, 3(5), 7-15.

The long term exposure to CO2 can be fatal to human lives resulting in chronic inflammation, kidney failure, bone atrophy, and loss of brain function. Human tissue calcification associated with carbonic anhydrase, the enzyme that converts CO2 in the body, along with other protein malfunctions, may be an existential threat.

The research and study indicate that CO2 concentration has increased in the past decades and will continue to rise in the future if
mitigation measures have not been applied properly. The rise in CO2 will be associated with the rise in cancers, neurological disorders, and other conditions.

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    • Bierwirth, P. N. (2018). Carbon dioxide toxicity and climate change: a major unapprehended risk for human health. Web Published: ResearchGate, 10.
    • Guais, A., Brand, G., Jacquot, L., Karrer, M., Dukan, S., Grévillot, G., … & Schwartz, L. (2011). Toxicity of carbon dioxide: a review. Chemical research in toxicology, 24(12), 2061-2070.
    • Rice, S. A. (2014). Human health risk assessment of CO2: survivors of acute high-level exposure and populations sensitive to prolonged low-level exposure. environments, 3(5), 7-15
    • Schmidt S. 2020. CO2 is trending: See the latest atmospheric concentrations data on Twitter. CSIROscope 28 February,
    • Shusterman, D. J., & Balmes, J. R. (1997). A comparison of two methods for determining nasal irritant sensitivity. American journal of rhinology, 11(5), 371-378.
    • Warburg, O. (1924) Ueber den Stoffwechsel der Tumoren. Biochem. Z. 152, 319–344
    • accessed on 02-03-2022

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