Rising levels of carbon dioxide in the atmosphere may already be influencing human biology. New research has identified long-term changes in blood chemistry that appear to track rising atmospheric CO2, raising concerns that an important blood marker could approach the upper end of its healthy range within the next several decades.
The findings may be particularly important for children and teenagers. Because their bodies are still developing, younger generations are expected to experience the greatest lifetime exposure to elevated atmospheric CO2.
In a study published in Air Quality, Atmosphere and Health, scientists from The Kids Research Institute Australia, Curtin University and The Australian National University (ANU) examined more than 20 years of U.S. population health data. They found persistent changes in several measures of blood chemistry that closely followed the upward trend in atmospheric CO2.
The researchers used information from the U.S. National Health and Nutrition Examination Survey (NHANES), analyzing blood test results from roughly 7,000 people at two-year intervals between 1999 and 2020.
Since 1999, average serum bicarbonate levels have increased by about 7 percent. Bicarbonate is a blood marker closely associated with carbon dioxide in the body. During the same period, average levels of calcium and phosphorus decreased.
Those biological trends occurred as atmospheric CO2climbed from about 369 parts per million (ppm) in 2000 to more than 420 ppm today.
Study author Associate Professor Alexander Larcombe said the results indicate that the body may already be adjusting to changes in the composition of the atmosphere.
“What we’re seeing is a gradual shift in blood chemistry that mirrors the rise in atmospheric carbon dioxide, which is driving climate change,” A/Prof Larcombe said.
How the Body Responds to More CO2
Bicarbonate is essential for regulating the body’s acid-base balance. As CO2 increases, the body can retain additional bicarbonate to help keep blood pH stable. Although this response helps preserve that balance, maintaining it over long periods could have physiological effects.
“If current trends continue, modeling indicates average bicarbonate levels could approach the upper limit of today’s accepted healthy range within 50 years,” A/Prof Larcombe said
“Calcium and phosphorus levels could also reach the lower end of their healthy ranges later this century.”
As atmospheric carbon dioxide increases, humans have no option but to breathe in more of it, which increases blood acidity. The body has ways to buffer this, including the kidneys producing and retaining more bicarbonate, which plays a key role in controlling blood acidity.
Average blood bicarbonate levels have increased by 7% since 1999, closely tracking the rise of in atmospheric carbon dioxide over the same period, according to the study, published last month in the journal Air Quality, Atmosphere and Health.
If these trends continue, bicarbonate in human blood could “reach unhealthy levels” within the next 50 years, the study concluded.
The scientists also looked at levels of calcium and phosphorus. One of the ways the body deals with blood being a little acidic is for bones to absorb some of the excess carbon dioxide and lock it away as calcium carbonate and calcium phosphate. The kidneys can also become less efficient at holding onto calcium.
While the evidence suggests a link between rising carbon dioxide and shifts in blood chemistry, the authors caution more work is needed to confirm it.
The study did not take into account other potential influencing factors including people’s diets, medications, kidney function, rates of obesity or the amount of time people spend indoors, where CO2 levels tend to be higher.
Normally, your body is very good at maintaining a stable pH (around 7.35 to 7.45). When CO2 levels rise, your body uses two main defense mechanisms to stop the blood from becoming too acidic:
- The Bicarbonate Buffer: Your body increases the levels of bicarbonate (HCO3–) to help neutralize the acid. The new study specifically noted that baseline bicarbonate levels in the general population are now trending upward as a compensatory response to the 420+ ppm of CO2 in the atmosphere.
- The Bone “Bank”: To get enough bicarbonate and other minerals to buffer the acid, the body may actually draw calcium and phosphorus from the bones. The study suggests this is why researchers are seeing a steady decrease in blood calcium and phosphorus alongside the rise in CO2.
In the past, these pH shifts usually only happened to people with lung diseases (like Chronic Obstructive Pulmonary Disease) or in poorly ventilated rooms. The significance of the new report is the finding that global atmospheric CO2 has now reached a level where it is creating a “permanent and growing change in human blood chemistry” for everyone, regardless of their health or indoor environment. In summary, our blood is becoming more acidic (lower pH) because the higher concentration of CO2 in the air makes it harder for our lungs to “offload” the gas, causing it to build up in the bloodstream and turn into carbonic acid.