Blood bicarbonate up about 7% while calcium and phosphorus down as atmospheric CO2 rises

Between 1999 and 2020, average serum bicarbonate levels in the U.S. population increased by about 7 percent, while average calcium and phosphorus levels decreased. These changes occurred as atmospheric carbon dioxide rose from about 369 parts per million to more than 420 parts per million. The researchers found that the blood chemistry trends closely followed the upward trend in CO2 over the same period.

The authors propose that rising atmospheric CO2 should be considered a long-term public health factor that warrants monitoring alongside traditional climate risks. Recognizing this shift may require integrating CO2 levels into routine health assessments and updating reference ranges for blood biomarkers as needed. Such an approach would treat CO2 not only as an environmental driver but also as a variable influencing human physiology.

Importantly, the study identifies an association rather than proving a direct cause-effect relationship between CO2 and the observed blood changes. The authors note that the body’s compensatory mechanisms for acid-base balance have limits, and if CO2 continues to rise beyond those limits bicarbonate could exceed healthy ranges. Consequently, the current adaptive response may cease to be effective once CO2 surpasses the range to which humans are historically adapted.

The analysis relies on NHANES data from the United States. The investigators emphasize that further research is needed to confirm whether the observed trends will persist and to clarify the physiological mechanisms involved. Until such work is done, projections about future limits remain model-based and uncertain.