Growing levels of carbon dioxide (CO₂) in the atmosphere could be influencing human blood chemistry, raising fresh concerns about the broader health implications of climate change, a new study has indicated.
The research, led by respiratory physiologist Alex Larcombe, found patterns in human blood composition that appear to track the steady rise in atmospheric CO₂ over the past two decades.
Larcombe, who heads respiratory environmental health at The Kids Research Institute Australia, said he initially doubted the idea when it was first suggested.
However, further investigation alongside Philip Bierwith revealed trends the researchers described as concerning.
The scientists analysed health records from the United States National Health and Nutrition Examination Survey, covering about 7,000 individuals every two years between 1999 and 2020.
Their findings showed that as atmospheric CO₂ levels climbed from about 300 parts per million (ppm) historically to over 420 ppm today, measurable changes occurred in markers linked to blood acidity.
According to the study published in Air Quality, Atmosphere and Health, average bicarbonate levels in human blood rose by approximately seven per cent over the study period a change believed to reflect the body’s response to increased acidity caused by higher CO₂ intake.
Bicarbonate plays a crucial role in stabilising blood pH, with the kidneys helping regulate its levels.
The researchers warned that if the trend continues, bicarbonate concentrations could reach unhealthy levels within the next 50 years.
In addition, the study observed declines in essential minerals. Blood calcium levels dropped by about two per cent, while phosphorus levels fell by roughly seven per cent over the same period.
Scientists explained that one way the body copes with increased acidity is by using bones to absorb excess CO₂, potentially reducing circulating levels of these minerals over time.
The study cautioned that continued decline could push calcium and phosphorus levels below healthy thresholds before the end of the century.
Despite the findings, the researchers noted that the results do not establish a direct cause-and-effect relationship.
They acknowledged that other factors such as diet, medication, kidney health, obesity, and time spent indoors where CO₂ concentrations are often higher were not fully accounted for.
“We cannot say with certainty that climate change alone is responsible for these changes,” Larcombe said, adding that further investigation is required.
Experts say the implications of such changes remain unclear, particularly over long-term exposure.
Some studies suggest the human body can adapt to higher CO₂ levels through increased breathing and bicarbonate regulation. However, emerging evidence, especially from animal research, points to possible effects including neurological damage and altered heart function.
Short-term exposure to elevated CO₂ levels, particularly in indoor environments, has also been linked to reduced cognitive performance and impaired decision-making.
Commenting on the findings, Kristie Ebi said the issue has been raised in previous studies but remains underexplored.
She noted that while existing research does not indicate severe health effects at projected CO₂ levels, potential risks for vulnerable populations cannot be ruled out.
Researchers emphasised that more studies are needed to fully understand the long-term health consequences of rising carbon emissions.
They added that beyond environmental concerns, increasing CO₂ levels may represent an emerging public health issue requiring closer attention.
