New Study Links Rising Atmospheric CO2 Levels to Changes in Human Blood Chemistry

Rising levels of carbon dioxide (CO2) in the atmosphere may significantly influence human biology, according to recent research. A study published in *Air Quality, Atmosphere and Health* has identified long-term alterations in blood chemistry that correlate with increasing atmospheric CO2 levels. This raises concerns that key blood markers could approach the upper limits of their healthy ranges within the coming decades, particularly affecting children and teenagers whose developing bodies will face the greatest exposure.

Researchers from The Kids Research Institute Australia, Curtin University, and The Australian National University (ANU) examined over 20 years of U.S. population health data, utilizing information from the National Health and Nutrition Examination Survey (NHANES). They analyzed blood test results from about 7,000 participants, collected at two-year intervals from 1999 to 2020. The study found a 7 percent increase in average serum bicarbonate levels alongside a decline in average calcium and phosphorus levels, paralleling a rise in atmospheric CO2 from about 369 parts per million (ppm) in 2000 to over 420 ppm today.

Study author Associate Professor Alexander Larcombe noted, "What we're seeing is a gradual shift in blood chemistry that mirrors the rise in atmospheric carbon dioxide, which is driving climate change." Bicarbonate, which plays a crucial role in maintaining the body's acid-base balance, is directly linked to CO2 levels. As CO2 concentrations rise, the body retains more bicarbonate to stabilize blood pH. While this adjustment can safeguard physiological balance, prolonged retention may have unanticipated effects.

Modeling suggests that if current trends persist, bicarbonate levels could reach the upper limit of the accepted healthy range within 50 years, with calcium and phosphorus potentially nearing the lower end of their healthy thresholds later in the century. Humans have evolved with atmospheric CO2 levels between 280 to 300 ppm, and the past decade has seen an average annual increase of approximately 2.6 ppm, with 2024 alone recording a rise of 3.5 ppm.

Fellow author Dr. Phil Bierwirth, a retired environmental geoscientist associated with the ANU Emeritus Faculty, emphasized that while the study does not establish a definitive cause-and-effect relationship, the consistency of the observed changes across a broad population merits attention. "It appears we are adapted to a range of CO2 in the air that may now have been surpassed," he stated.

The findings indicate that rising atmospheric CO2 is not just an environmental concern but may also pose long-term public health risks. According to Larcombe, "This suggests there may be gradual physiological changes occurring at a population level, and that's something we should be monitoring as part of future climate change policy."

The researchers advocate for ongoing monitoring of atmospheric composition in conjunction with biological markers to assess how gradual environmental changes influence human health over decades. Furthermore, while reducing CO2 emissions remains critical for curbing global warming, it may also play a vital role in safeguarding long-term human health.

Associate Professor Larcombe is part of the Wal-yan Respiratory Research Centre, a collaboration involving The Kids Research Institute Australia, Perth Children's Hospital, and the Perth Children's Hospital Foundation.