Rising CO2 Levels Detected in Human Blood, Study Finds

A recent study suggests that the increasing levels of carbon dioxide (CO2) in Earth’s atmosphere are not only impacting the climate but are also detectable and measurable in human blood chemistry. Researchers have identified shifts in blood chemistry over the past two decades that correlate with rising atmospheric CO2 levels.

The Link Between Atmospheric CO2 and Blood Chemistry

Scientists analyzed data from the US National Health and Nutrition Examination Survey (NHANES), examining blood samples from approximately 7,000 Americans collected between 1999 and 2020. The analysis revealed a rise in average blood bicarbonate levels from 23.8 to 25.3 milliequivalents per liter – an increase of roughly 7 percent, or 0.34 percent per year. This increase mirrored the concurrent rise in atmospheric CO2.

“What we’re seeing is a gradual shift in blood chemistry that mirrors the rise in atmospheric carbon dioxide, which is driving climate change,” says respiratory physiologist Alexander Larcombe of Curtin University in Australia.

How CO2 Impacts Blood Chemistry

In the bloodstream, CO2 is converted into bicarbonate, a compound that helps maintain the body’s pH balance. While bicarbonate is normally beneficial, the study suggests that increasing levels may indicate a physiological response to higher atmospheric CO2. The researchers also observed a decrease in calcium (by 2 percent) and phosphorus (by 7 percent) levels during the study period. This is potentially linked to the body’s attempt to regulate blood pH, as bones can release these minerals to buffer acidity when CO2 dissolves in the bloodstream.

Current and Future Implications

Currently, these shifts are small and remain within the body’s acceptable range. However, the researchers’ modeling suggests that if CO2 levels continue to rise at the current rate, average bicarbonate levels could approach the upper limit of today’s healthy range within 50 years. Calcium and phosphorus levels could also reach the lower complete of their healthy ranges later this century.

“I actually think that what we are seeing is since our bodies are not adapting,” says retired geoscientist Phil Bierwirth, affiliated with the Australian National University. “It appears we are adapted to a range of CO2 in the air that may now have been surpassed.”

Historical CO2 Levels and Human Adaptation

According to the fossil record, atmospheric CO2 levels remained relatively stable for at least 150,000 years of Homo sapiens history, fluctuating between 280 and 300 parts per million (ppm). However, in recent decades, CO2 levels have risen dramatically, from around 369 ppm in 2000 to approximately 420 ppm today.

The Bigger Picture: CO2 Emissions and Climate Change

The United States is a significant contributor to global CO2 emissions. In 2022, the US emitted 4,853,780,240 tons of CO2, representing 12.6% of the global total. Per capita emissions were 14.21 tons, an increase of 1.4% from 2021. The US environmental footprint is substantial; if everyone lived like the average American, it would take five Earths to sustain that level of consumption.

The study, published in Air Quality, Atmosphere & Health, highlights the potential for long-term physiological changes as atmospheric CO2 continues to rise, reinforcing the urgency of limiting CO2 emissions to mitigate climate change.