As global carbon dioxide levels reach heights never before experienced by humans, scientists are warning of a potential new impact beyond climate change: subtle shifts in human blood chemistry.
Atmospheric COâ‚‚ concentrations have surged past 420 parts per million (ppm), far above the roughly 300 ppm levels in which humans evolved. While the environmental consequences of this rise are well documented, emerging research suggests it could also be affecting the human body itself.
A study led by respiratory physiologist Alex Larcombe of The Kids Research Institute Australia analyzed more than two decades of US health data. Working with Philip Bierwith from Australian National University, the team identified trends in blood chemistry that appear to mirror rising atmospheric COâ‚‚.
Using data from the US National Health and Nutrition Examination Survey (NHANES), which tracked around 7,000 individuals every two years from 1999 to 2020, researchers focused on biomarkers linked to carbon dioxide exposure.
Key findings
The study found that:
- Blood bicarbonate levels increased by approximately 7% over the study period
- Blood calcium levels decreased by about 2%
- Phosphorus levels dropped by roughly 7%
These changes are consistent with how the human body responds to increased carbon dioxide. As COâ‚‚ levels rise, the body maintains balance by producing more bicarbonate to regulate blood acidity. Bones may also help buffer acidity by releasing minerals such as calcium and phosphorus.
If these trends continue, researchers warn that some of these markers could reach unhealthy levels within decades.
A cautious interpretation
Despite the findings, scientists stress that the link is not yet definitive.
The study did not fully account for other factors that can influence blood chemistry, including diet, medications, obesity, kidney health, and time spent indoors—where CO₂ concentrations are often higher.
“We can’t say for certain that these changes are 100% due to climate change,” Larcombe said. However, he added that the results suggest rising CO₂ should be viewed not only as an environmental issue but also as a potential long-term public health concern.
What does it mean for human health?
The long-term health implications remain unclear.
Some studies suggest the human body can adapt to higher CO₂ levels without major harm by adjusting breathing and blood chemistry. However, Larcombe cautioned that lifetime exposure and cumulative effects—especially for younger generations—are still poorly understood.
Research on animals has shown possible impacts such as neurological changes and altered heart rates, while studies in humans have linked elevated indoor COâ‚‚ levels to reduced cognitive performance and decision-making ability.
Independent expert Kristie Ebi from the University of Washington noted that while the issue has been raised before, evidence of significant health effects in humans remains limited. She added that even if widespread impacts are unlikely, vulnerable groups could still be affected.
An emerging area of concern
Scientists emphasize that the findings are not cause for panic but highlight the need for further research.
“It’s not that we’re all going to die,” Larcombe said. “It’s that there’s something going on, and we need to understand it.”
As atmospheric COâ‚‚ continues to rise, researchers say understanding its full impact on human health is becoming increasingly urgent.
