Rising Atmospheric CO2 May Be Altering Human Blood Chemistry, Scientists Warn

Scientists analysing US National Health and Nutrition Examination Survey data from 1999 to 2020 have found that serum bicarbonate levels in approximately 7,000 tracked individuals rose by roughly 7 per cent in parallel with rising atmospheric CO2, from a baseline that closely mirrors the increase in CO2 from 280 ppm in 1960 to 428.62 ppm at the NOAA Mauna Loa Observatory. Researchers warn that at the current rate of increase, blood bicarbonate could reach the upper healthy limit of 30 mEq/L by 2076.

The study identified significant shifts in three primary biomarkers: serum bicarbonate rose approximately 7 per cent since 1999, while mean serum calcium levels decreased by about 2 per cent and phosphorus levels fell by roughly 7 per cent. Most recent NHANES measurements recorded serum bicarbonate at 25.3 mEq/L in 2019-2020, against a venous upper healthy limit of 30 mEq/L. The researchers explain that when humans inhale excess CO2, it is hydrated into carbonic acid, which dissociates into hydrogen ions and bicarbonate; to buffer the acidity, the body retains more bicarbonate while bones release calcium and phosphate, eventually leading to their depletion through renal excretion.

The findings carry particular concern for children and adolescents, whose developing bodies will be exposed to rising CO2 for the longest time. Hypocalcemia — below-normal blood calcium — causes numbness, muscle spasms and confusion, while hypophosphatemia can trigger respiratory alkalosis and diabetic ketoacidosis. Elevated bicarbonate and CO2 levels may cause proteome malfunction including protein misfolding and endoplasmic reticulum stress, potentially contributing to diabetes and neurological disorders. Previous studies linked moderate CO2 exposure below 1,000 ppm to impaired learning, reduced cognitive ability and increased anxiety.

Assuming a linear increase rate of approximately 0.34 per cent per year, the lower healthy limits for calcium and phosphorus could be reached in 2099 and 2085 respectively. The authors state that changes observed in human blood chemistry over the past quarter century are 'greatly concerning' and suggest the human body may already be in a period of permanent physiological compensation for atmospheric CO2. The study calls for significant reductions in CO2 emissions to prevent a widespread public health crisis, framing climate action as a matter of direct human physiological health rather than solely an environmental or economic concern.

Key figure — 7 per cent increase in serum bicarbonate levels among NHANES participants between 1999 and 2020