Perhaps you’ve wondered why there seems to be more public interest in breathing techniques emphasizing development of a tolerance to higher carbon dioxide levels? As some parts of the world head into window-closing weather, this comprehensive paper from Environmental Science Advances; (Volume 4, Issue 9, 11 June 2025, Pages 1364-1372, authored by Ugo Bardi, et. al.) highlights an under-appreciated aspect of a crucial tie between environmental health and human health: ‘Our study highlights an extremely important subject, unfortunately much neglected and ignored so far. It provides a new perspective on the urgent need to reduce CO2 emissions, independent of their climatic effects.’
While providing a new perspective on the increasing human health-related importance of ventilation for indoor environments, the below partial chart (included in their paper) is just the beginning of what these authors offer towards contextualization of carbon dioxide levels, not only in the indoor environment, but on a more all-encompassing stage.
| CO2concentration ppm | Biochemical effects | Notes |
|---|---|---|
| 180–280 | Evolution of large brains during the Pleistocene | Lowest values ever in Earth’s history |
| 280 | Normal value for the current ecosystem | Stable during the Holocene |
| 420 | Marine acidification, global greening, and metabolic disruption | Current value |
| 600–1200 | Limits to CO2 plant fertilization | Above these levels the fertilization effect becomes negative |
| 1000 | Safe indoor limit | Measurable brain slowdown observed above 600 ppm for short-term exposure |
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