Rising CO2 alters human blood chemistry, study finds

Rising atmospheric carbon dioxide is linked to long-term shifts in human blood chemistry, according to a study published in Air Quality, Atmosphere and Health on August 15, 2026. Researchers found that average serum bicarbonate levels in the U.S. population rose by about 7 percent between 1999 and 2020, while calcium and phosphorus levels fell.

The study, led by Associate Professor Alexander Larcombe of The Kids Research Institute Australia, Curtin University and The Australian National University, analyzed blood test results from roughly 7,000 people at two-year intervals using data from the U.S. National Health and Nutrition Examination Survey. The changes closely tracked the rise in atmospheric CO2, which climbed from about 369 parts per million in 2000 to more than 420 ppm today.

The findings matter because bicarbonate helps regulate the body's acid-base balance, and prolonged elevation could have physiological effects. Modeling cited by Larcombe indicates that if current trends continue, average bicarbonate levels could approach the upper limit of today's accepted healthy range within 50 years, while calcium and phosphorus could reach the lower end of their healthy ranges later this century.

Co-author Dr Phil Bierwirth, a retired environmental geoscientist affiliated with the ANU Emeritus Faculty, cautioned that the study does not establish direct causation. However, he noted that humans evolved when atmospheric CO2 was approximately 280 to 300 ppm, and recent annual increases—averaging 2.6 ppm over the past decade and 3.5 ppm in 2024 alone—may have surpassed the range to which our bodies are adapted.

The researchers recommend monitoring atmospheric composition alongside biological markers across populations, arguing that rising CO2 should be considered a long-term public health factor in climate policy. Larcombe, part of the Wal-yan Respiratory Research Centre, said the gradual physiological changes at a population level warrant attention, even if no sudden health threshold is crossed.