Rising levels of carbon dioxide (CO₂) in the atmosphere may be associated with gradual changes in human blood chemistry, according to new research examining more than two decades of population health data.
The study, published in Air Quality, Atmosphere and Health, was conducted by researchers from The Kids Research Institute Australia, Curtin University and The Australian National University (ANU). Scientists analysed blood test results from approximately 7,000 people using data from the US National Health and Nutrition Examination Survey (NHANES) collected between 1999 and 2020.
Blood Chemistry Changes Track Rising CO₂
Researchers found that average serum bicarbonate levels increased by around 7% between 1999 and 2020. Bicarbonate is an important blood marker involved in maintaining the body's acid-base balance and is closely linked to carbon dioxide levels.
During the same period, average blood calcium and phosphorus levels declined.
The observed changes occurred alongside a rise in atmospheric CO₂ concentrations, which increased from approximately 369 parts per million (ppm) in 2000 to more than 420 ppm today.
Researchers say the findings suggest that changes in atmospheric CO₂ may be reflected in human physiology, although the study does not establish a direct cause-and-effect relationship.
Bicarbonate Levels Could Approach Upper Healthy Limit
As atmospheric CO₂ rises, the body can retain additional bicarbonate to help maintain normal blood pH. Researchers warn that prolonged changes in this regulatory process could have implications for human health.
Modelling suggests that if current trends continue, average blood bicarbonate levels could approach the upper end of the currently accepted healthy range within about 50 years. Calcium and phosphorus levels could potentially move towards the lower end of their healthy ranges later this century.
Younger Generations May Face Greater Exposure
The findings could be particularly relevant to children and teenagers, whose bodies are still developing and who are expected to experience greater lifetime exposure to higher atmospheric CO₂ concentrations.
Humans evolved in an environment where atmospheric CO₂ levels were roughly 280 to 300 ppm. Atmospheric concentrations have increased substantially since then, with the annual rise averaging around 2.6 ppm over the past decade.
Researchers Urge Further Monitoring
Scientists emphasise that the study does not prove that increasing atmospheric CO₂ is directly responsible for the observed changes in blood chemistry. However, the consistency of the trends across a large population warrants further investigation.
Researchers recommend monitoring atmospheric CO₂ levels alongside biological markers to better understand whether long-term environmental changes are influencing human physiology.
The findings also introduce a potential new dimension to climate-related health risks. Beyond established concerns such as heatwaves, extreme weather and rising sea levels, scientists say atmospheric CO₂ may need to be considered as a long-term public health factor.
CO₂ Reduction Could Have Additional Health Benefits
Reducing CO₂ emissions remains critical for limiting global warming and its established environmental effects. The researchers suggest that lower atmospheric CO₂ levels could potentially offer additional long-term health benefits if future studies confirm a connection between rising concentrations and physiological changes.
Further research will be needed to determine the mechanisms behind the observed blood chemistry trends and establish whether rising atmospheric CO₂ directly contributes to these changes in human health.
Source:
Materials provided by The Kids Research Institute Australia. Note: Content may be edited for style and length.
Reference:
Alexander N. Larcombe, Phil N. Bierwirth. Carbon dioxide overload, detected in human blood, suggests a potentially toxic atmosphere within 50 years. Air Quality, Atmosphere, 2026; 19 (3) DOI: 10.1007/s11869-026-01918-5
