As atmospheric carbon dioxide has risen over the past two decades, a marker in human blood appears to have shifted alongside it — a subtle change that researchers say is worth watching, but not a cause for alarm.
Scientists at the Kids Research Institute Australia, with Curtin University and the Australian National University, analyzed U.S. NHANES health-survey data from about 7,000 people, collected every two years between 1999 and 2020. They found blood bicarbonate — a molecule that helps regulate the blood’s acid-base balance — rose roughly 7% over that period, while calcium and phosphorus edged down. The changes tracked the rise in atmospheric CO2, from about 369 parts per million in 2000 to over 420 today. The work appeared in Air Quality, Atmosphere and Health (2026).
The proposed link
The idea is that as environmental CO2 rises, the body retains more bicarbonate to keep blood pH stable. “What we’re seeing is a gradual shift in blood chemistry that mirrors the rise in atmospheric carbon dioxide,” the researchers said. Their modeling suggests bicarbonate could approach the upper end of the healthy range within about 50 years — a concern they flag especially for children, who face a lifetime of exposure.
Important caveats
The researchers are explicit that this is a correlation, not proof of cause: the study shows two trends moving together across a large population, not that rising CO2 directly changes blood chemistry or harms health. It’s preliminary epidemiological evidence that, they argue, warrants continued monitoring — an intriguing signal rather than a settled finding.