Observational study finds increased serum bicarbonate levels linked to rising atmospheric CO2 — Evidence Review
Published in Air Quality, Atmosphere and Health, by researchers from The Kids Research Institute Australia, Curtin University, The Australian National University
Researched by
— the AI search engine for science
Table of Contents
Rising atmospheric carbon dioxide may already be altering human blood chemistry, a new study finds, with average serum bicarbonate levels increasing by about 7% since 1999. Related research largely supports the link between environmental change and shifts in blood biomarkers, though direct cause-and-effect between atmospheric CO2 and human biochemistry remains to be fully established, as discussed by the study organization.
- Several studies confirm that blood bicarbonate closely tracks environmental and metabolic changes, and that deviations from the normal range can impact health outcomes, particularly in populations with chronic kidney disease 1 3 5.
- Climate-related alterations in blood chemistry have also been documented in both animal and human studies, indicating that environmental factors—including temperature, humidity, and atmospheric gases—can influence physiological markers in blood 9 10 11.
- While the new findings are consistent with broader literature on environmental impacts on blood biomarkers, most prior human studies focus on acute exposures or disease states rather than gradual, population-level shifts over decades 1 2 5.
Study Overview and Key Findings
This study addresses a timely and underexplored question: Are rising atmospheric CO2 levels subtly affecting human physiology on a population scale? By leveraging two decades of national health survey data, the researchers sought to identify trends in blood chemistry that might reflect adaptation (or lack thereof) to modern atmospheric conditions. The study is notable for its focus on healthy individuals across a large, representative cohort, rather than specific patient groups or acute exposures, and for raising the possibility of a new dimension of climate risk beyond immediate environmental hazards.
| Property | Value |
|---|---|
| Study Year | 2023 |
| Organization | The Kids Research Institute Australia, Curtin University, The Australian National University |
| Journal Name | Air Quality, Atmosphere and Health |
| Authors | Associate Professor Alexander Larcombe, Dr Phil Bierwirth |
| Population | U.S. population health data |
| Sample Size | n=7000 |
| Methods | Observational Study |
| Outcome | Changes in blood chemistry related to atmospheric CO2 levels |
| Results | Average serum bicarbonate levels increased by about 7% since 1999. |
Literature Review: Related Studies
To contextualize these findings, we searched the Consensus paper database, which includes over 200 million research papers. The following search queries were used to identify relevant literature:
- CO2 levels serum bicarbonate changes
- human blood bicarbonate increase 1999
- climate change blood chemistry effects
Related Studies Table
| Topic | Key Findings |
|---|---|
| How do serum bicarbonate and CO2 levels relate to health risks in humans? | - Both low and high serum bicarbonate levels are linked to increased mortality in patients with chronic kidney disease (CKD), suggesting a U-shaped risk relationship 1. - Serum total CO2 is a strong surrogate for bicarbonate concentration, but may not always accurately reflect acid-base status, especially in CKD and hemodialysis 3 5. |
| Does climate change affect blood chemistry and physiological markers? | - Climate change is associated with alterations in biochemical markers of kidney function and blood parameters in both humans and animals, likely reflecting physiological responses to environmental stressors 9 10 11. - Seasonal and environmental shifts can lead to measurable changes in blood markers, including in non-human species 10 11. |
| Are population-level blood chemistry changes observed outside of disease settings? | - Most previous studies focus on disease populations (e.g., CKD) or acute exposures; population-scale, long-term shifts in blood chemistry in healthy individuals are less well documented 1 2 5. - The new study is among the first to document a persistent, population-wide increase in serum bicarbonate paralleling rising atmospheric CO2 6. |
| What are the methodological challenges in assessing blood biomarkers in environmental studies? | - Accurate measurement of serum bicarbonate can be affected by factors such as sample handling, measurement technique, and interference from other blood components (e.g., lipids) 4 7. - Standardization and careful interpretation are essential for using blood biomarkers to monitor environmental and climate impacts 4 7. |
How do serum bicarbonate and CO2 levels relate to health risks in humans?
The relationship between serum bicarbonate, CO2 levels, and health outcomes has been well-explored in the context of kidney disease and acid-base disorders. Several studies show that deviations from the normal bicarbonate range are associated with increased mortality, particularly in patients with CKD. Total CO2 is often used as a surrogate for bicarbonate, but its accuracy can vary across clinical settings.
- Both low and high serum bicarbonate levels are independently linked to mortality in CKD, highlighting the importance of maintaining acid-base balance 1.
- Serum total CO2 and bicarbonate are highly correlated, but autoanalyzer methods may be unreliable in certain cases (e.g., hyperlipidemia) 3 4.
- In hemodialysis patients, total CO2 alone may misclassify acid-base status, emphasizing the need for full blood gas analysis 5.
- The new study extends these observations to the general population, suggesting that environmental changes may gradually shift blood bicarbonate levels even outside of overt disease 6.
Does climate change affect blood chemistry and physiological markers?
A growing body of research supports the idea that climate change and environmental factors can influence blood chemistry in both humans and animals. Studies document seasonal, temperature-driven, and atmospheric shifts in key physiological and biochemical markers.
- Climate variation significantly impacts kidney function markers, blood pressure, and other parameters in healthy individuals, with implications for chronic disease risk 9.
- Animal studies show that climate-induced stressors, such as temperature and acidity, cause measurable changes in blood chemistry, though responses vary by species 10 11.
- Similar patterns are observed in horses, where blood parameters fluctuate with seasonal changes in temperature and humidity 11.
- The new study's findings are consistent with this broader literature, adding evidence that atmospheric CO2 may be one environmental driver of such trends in humans 6.
Are population-level blood chemistry changes observed outside of disease settings?
While most prior research has focused on specific patient populations or acute exposures, there is limited evidence on whether gradual, population-level shifts in blood biomarkers occur in healthy humans due to environmental change. The new study is notable for documenting such a trend over two decades.
- Previous studies largely address disease contexts (e.g., CKD) or short-term interventions, rather than long-term, population-wide effects 1 2 5.
- The observed 7% rise in serum bicarbonate across a healthy U.S. population from 1999–2020, paralleling atmospheric CO2 increases, is a unique contribution 6.
- This suggests a potential new public health dimension of climate change, beyond the well-established acute effects of heatwaves or pollution 8.
- Further research is needed to determine the clinical significance of these gradual biochemical shifts in healthy populations.
What are the methodological challenges in assessing blood biomarkers in environmental studies?
Assessing blood biomarkers in the context of environmental or climate research involves several technical and interpretive challenges. Accurate measurement, standardization, and avoidance of confounding factors are essential for reliable conclusions.
- Autoanalyzer-calculated bicarbonate levels can be inaccurate in patients with severe hyperlipidemia due to interference with photometric measurement 4.
- In both human and animal studies, careful attention to sampling, handling, and analysis protocols is necessary to avoid spurious results 4 7.
- Blood biomarker studies require adapted protocols for different species, careful design, and immediate processing to ensure valid outcomes 7.
- The new study's use of established, standardized U.S. health survey data provides robust methodological grounding for its findings 6.
Future Research Questions
While this study offers novel insights into the possible physiological impacts of rising atmospheric CO2, several important questions remain. Future research is needed to clarify causality, assess long-term health implications, and explore biological mechanisms and population differences.
| Research Question | Relevance |
|---|---|
| What are the long-term health consequences of elevated serum bicarbonate in the general population? | Understanding whether gradual increases in serum bicarbonate have adverse health effects, as seen in CKD patients, is crucial for public health policy 1 5. |
| Does reducing atmospheric CO2 reverse changes in human blood chemistry? | Identifying whether interventions to lower atmospheric CO2 can restore blood markers to baseline would clarify causality and inform climate and health policy 6 8. |
| Are certain populations more susceptible to blood chemistry changes from CO2 exposure? | Children, adolescents, and those with preexisting health conditions may be at greater risk; understanding demographic differences will help target monitoring and intervention efforts 6 9. |
| What biological mechanisms mediate the relationship between atmospheric CO2 and serum bicarbonate? | Elucidating how atmospheric CO2 translates into physiological changes at the cellular and systemic levels is essential for understanding risks and identifying biomarkers 3 6. |
| How do other environmental factors (climate, pollution) interact with CO2 to impact blood chemistry? | Simultaneous exposure to multiple environmental stressors may have additive or synergistic effects on blood chemistry, complicating risk assessment and public health responses 9 10. |
This comprehensive review highlights that while mounting evidence links environmental change to shifts in blood chemistry, more research is needed to determine the health significance, underlying mechanisms, and optimal strategies for monitoring and mitigating risk as atmospheric CO2 levels continue to rise.