CO2 Is Rewiring Our Blood Chemistry

Blood drawn from ordinary Americans over the last 20 years shows a chemical shift that closely tracks the rise of carbon dioxide in the air outside.

Quick Take

A new study found average blood bicarbonate rose about 7% in Americans between 1999 and 2020.
Researchers pulled the numbers from a huge, long-running federal health survey.
Calcium and phosphorus levels dropped over that same stretch.
Scientists say bicarbonate could near the edge of the healthy range within 50 years if the trend holds.

A Two-Decade Shift Shows Up In Federal Health Records

Researchers Neil Larcombe and Philip Bierwirth studied blood test results from the National Health and Nutrition Examination Survey, a huge United States government health project. They found the most recent measured serum bicarbonate level, taken in 2019 and 2020, sat at 25.3 milliequivalents per liter. That number marks roughly a 7% climb since 1999.

Larcombe, a geoscientist, and Bierwirth, an emeritus researcher at the Australian National University, spent months combing through more than 20 years of American health data. They lined up those blood test results against the well-documented rise in atmospheric carbon dioxide over the same period. The two trends moved together, year after year.

How Carbon Dioxide Rewires Blood Chemistry

The link makes biological sense. Carbon dioxide dissolves into blood and gets converted into bicarbonate, a compound the body uses to keep its acid-base balance steady. Scientists have long known that rising carbon dioxide in the air pushes more of the gas into blood, raising blood pressure and altering blood flow in minutes, not years.

Calcium and phosphorus tell the other half of the story. Both minerals help buffer acid in the blood alongside bicarbonate, and both declined steadily across the same 20-year window the researchers studied. Outlets covering the paper described the pattern as a matched set: bicarbonate up, calcium and phosphorus down, moving in step with rising carbon dioxide levels.

What The Trend Could Mean For The Decades Ahead

The researchers ran the numbers forward. If bicarbonate keeps climbing at its current pace, it could approach the upper edge of the accepted healthy range within about 50 years. Calcium and phosphorus, moving the opposite direction, could hit the low end of their healthy ranges by the end of this century.

This study shows that, due to climate change, our blood chemistry has shifted 7% since 1999 and will make us sick in appx. 50 years. It's called metabolic alkalosis. https://t.co/EaJxZen9Q7

— Karen Piper (@PiperK) August 18, 2026

Bierwirth has called the shift a warning sign worth watching closely, especially for children and young people who face a lifetime of rising exposure ahead of them. The study’s authors are careful to frame their bicarbonate and mineral data as indirect proxies tied to atmospheric carbon dioxide trends, not as direct proof that carbon dioxide alone drives every blood change measured.