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 increases in atmospheric CO.2raising concerns that an important blood marker could approach the upper end of its healthy range in the coming decades.
The findings may be particularly important for children and adolescents. Because their bodies are still developing, younger generations are expected to experience the greatest lifetime exposure to elevated levels of atmospheric CO.2.
Decades of blood data reveal a change
In a study published in Air quality, atmosphere and healthScientists from Kids Research Institute Australia, Curtin University and the Australian National University (ANU) examined more than 20 years of health data on the US population. They found persistent changes in several measures of blood chemistry that closely tracked the rising trend of atmospheric CO.2.
The researchers used data from the US National Health and Nutrition Examination Survey (NHANES), analyzing blood test results from about 7,000 people at two-year intervals between 1999 and 2020.
Since 1999, average serum bicarbonate levels have increased about 7 percent. Bicarbonate is a blood marker closely associated with carbon dioxide in the body. During the same period, average calcium and phosphorus levels decreased.
Those biological trends occurred as atmospheric CO.2 rose from approximately 369 parts per million (ppm) in 2000 to more than 420 ppm today.
Study author Associate Professor Alexander Larcombe said the results indicate the body may already be adapting to changes in the composition of the atmosphere.
“What we are seeing is a gradual change in blood chemistry that reflects the increase in atmospheric carbon dioxide, which is driving climate change,” Professor Larcombe said.
How the body responds to more CO2
Bicarbonate is essential to regulate the body’s acid-base balance. As CO2 increases, the body can retain additional bicarbonate to help keep blood pH stable. While this response helps preserve that balance, maintaining it for prolonged periods could have physiological effects.
“If current trends continue, modeling indicates that average bicarbonate levels could approach the upper limit of today’s accepted healthy range within 50 years,” Professor Larcombe said.
“Calcium and phosphorus levels could also reach the lower end of their healthy ranges by the end of this century.”
Humans evolved when atmospheric CO2 concentrations were approximately 280 to 300 ppm. Over the past decade, atmospheric levels have increased by an average of about 2.6 ppm each year, while 2024 alone saw an increase of 3.5 ppm.
Fellow author Dr Phil Bierwirth, a retired environmental geoscientist affiliated with the ANU Emeritus Faculty, emphasized that the study does not establish a direct cause-and-effect relationship. However, he said the consistency of the changes across a large population deserves attention.
“In fact, I think what we’re seeing is because our bodies are not adapting,” Dr. Bierwirth said.
“We seem to be adapted to a variety of CO2 in the air that perhaps has now been surpassed.
“The normal range maintains a delicate balance between the amount of CO2 is in the air, our blood pH, our breathing rate and blood bicarbonate levels.
“As CO2 In the air it is now higher than humans have ever experienced, it seems to be accumulating in our bodies. We may never be able to adapt in such a way that it is vitally important to limit atmospheric levels of CO2“.
A possible new dimension of climate risk
The researchers say the results suggest that increased atmospheric CO2 could represent a form of climate-related risk different from more familiar threats such as heat waves, extreme weather and sea level rise.
According to A/Prof Larcombe, the increase in CO2 It may need to be considered not only as an environmental concern, but also as a long-term public health factor that should be monitored.
“We’re not saying that people are going to suddenly get sick when we cross a certain threshold,” he said.
“But this suggests that gradual physiological changes may be occurring at the population level, and that is something we should monitor as part of future climate change policy.”
The researchers recommend monitoring the composition of the atmosphere along with biological markers in all populations. Tracking both along with established climate indicators could help scientists determine how slow environmental changes affect human biology over periods of decades.
CO2 The reduction could have health implications
Cut CO2 Emissions remain essential to limit global warming. The findings also raise the possibility that reducing emissions may play an additional role in protecting human health in the long term.
The researchers maintain that the possible physiological effects of increased CO2 It should therefore be considered in future climate policy debates, along with its stated environmental consequences.
Associate Professor Larcombe is part of the Wal-yan Respiratory Research Centre, a partnership between Kids Research Institute Australia, Perth Children’s Hospital and Perth Children’s Hospital Foundation.