The link between carbon dioxide (CO₂), the greenhouse effect, and global warming has been known since the 19th century. By continually pumping vast quantities of CO₂ into the atmosphere we are changing our climate and damaging our environment to an alarming extent. What has only recently been recognised, but should not be a surprise, is that increased atmospheric CO₂ is having a measurable impact on human physiology, and could exceed healthy limits within decades.
What do we know?
CO₂ is a by-product of cellular activity and is exhaled as a waste product. It’s possible to determine the levels of CO₂ in the human body by measuring the levels of bicarbonate in the blood.
However, CO₂ is not just a waste product. It plays a key role in regulating blood acidity (pH) and breathing rates. Too much (hypercapnia) or too little (hypocarbia) CO₂ in the blood can cause a variety of dangerous health conditions affecting respiratory, metabolic, and cognitive functions.
The negative impact of rising atmospheric CO₂ on human health has already been recognised. The urgent need for action has now been powerfully demonstrated in a recently published study (2026).
The study authors looked at recorded blood chemistry parameters, including bicarbonate, from around 7,000 people every two years between 1999 and 2020. The researchers were looking to see if there were any long-term trends in human blood biochemistry that may be the result of changes in global air composition – particularly CO₂ levels in the atmosphere.
The findings
It might seem like common sense that if you breathe in more CO₂ from the atmosphere, this would be reflected in CO₂ levels in the body. This study provides the scientific evidence that that is indeed the case: CO₂ levels in human blood increase in parallel to increases in atmospheric CO₂.
The research found that average blood bicarbonate levels in the study population increased from ~23.8 milliequivalents per litre (mEq/L) in 1999–2000 to ~25.3mEq/L (in 2019–2020), representing an increase of around 7%, consistent with a similar increase in atmospheric CO₂ over the same period.
If the current rate of increase in atmospheric CO₂ continues, the study tells us that the healthy maximum blood bicarbonate levels in humans (30mEq/L) will be reached by around 2076, or earlier if atmospheric CO₂ levels continue to increase.
Why this matters
Homo Sapiens first appeared in the fossil record around 150,000 years ago, and throughout our evolution atmospheric CO₂ levels were relatively stable at around 280 parts per million (ppm). We have evolved as a species to thrive at that level of CO₂.
In the last 50 years or so, atmospheric CO₂ has risen from 340 ppm or less to in excess of 420 ppm, and is currently increasing at more than 2ppm every year. Clearly humans will be inhaling more CO₂ than at any time in our evolution.
Impact on human health
Increasing levels of CO₂ in the blood lead to complex interactions and changes in blood chemistry (particularly blood acidity, calcium and phosphorous levels), bones, and kidneys. The study authors say: “ …we may have already entered a period where there is permanent and developing physiological compensation for CO₂ in our bodies.”
There is mounting evidence, for example studies of ‘sick building syndrome’, that even small, short-term increases in atmospheric CO₂ impact human physiology. The impact of life-long exposure, or exposure during periods of critical development, such as in the womb or as infants, is not yet fully understood, but studies have shown associated changes in respiration, circulation, cerebral electrical activity, heart rate, kidney calcification, oxidative stress, neural damage and inflammation.
The new research found that CO₂ in human blood increases in parallel with increases in atmospheric CO₂. It also found that both calcium and phosphorus show related decreases, and the mechanism for this is explained in the published results.
Calcium is essential for a healthy body, and low levels can impact almost every organ and system: “…calcium is essential in muscle contraction, oocyte activation (reproduction), building strong bones and teeth, blood clotting, nerve impulse transmission, regulating heart-beat and fluid balance within cells”.
Similarly, phosphorus is critical in metabolism, building DNA and RNA, growth, and muscle contraction. Low levels can lead to tissue hypoxia and cellular function disruption.
Another reason to take CO₂ seriously
While human physiology is very good at adapting to environmental changes, there is mounting evidence that we are rapidly approaching the point where we are no longer able to adapt to the speed and scale of CO₂ increases. The consequences could be devastating. Throughout our evolution as a species, atmospheric CO₂ levels were relatively stable at around 280 ppm so we had no need to evolve mechanisms to deal with much higher levels, and we are already above 420 ppm. And it’s not just the high levels of CO₂, it’s also the speed of increase that is unprecedented in human history. This latest research tells us we are heading to the safe limits of our bodies ability to handle atmospheric CO₂ levels in the next 50 years – by 2079. That’s within the lifetimes of many, and of our children and grandchildren.
To quote the researchers, this is “…a major issue presenting a risk to population health and an existential threat for many species especially given that the rise in atmospheric CO₂ may be a phenomenon that has significant momentum. Realistically, to mitigate this approaching threat, the alarm needs to be raised immediately. Unfortunately, currently there is little awareness or inclination for action on this issue.”
Much has been written about the impact of CO₂ on our climate, and the dangers posed by global warming as we continue to pump more and more CO₂ into our atmosphere. What is new in this latest research, is the direct impact of CO₂ levels on our health, independent of effects of climate changes on us and our planet.
You can’t say we weren’t warned!
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