Direct human health risks of increased atmospheric carbon dioxide
Atmospheric CO2’s direct human health risks from normal exposures merits urgent study. Evidence on exposures and effects raises questions about the healthfulness of indoor and outdoor air, particularly for vulnerable people, now and especially if we allow CO2 to keep building up in the atmosphere.
I vividly recall when I first thought there could be direct human health effects from breathing air with too much CO2 in it. A few years ago, I was in Taipei, suffering jetlag in the dark of 4 a.m., too early to rise. I reflected on conversations with a longtime mentor about TC Chamberlin’s work on carbon fluxes, and about carbon stores provisioning conditions suitable for the flourishing of life on earth. Chamberlin was a pioneering geologist who advanced some of the early geo-climate models. Other ideas came quickly to mind from work applying sustainability principles to public health. Specifically, increasing the concentration of even a naturally occurring compound like CO2 will eventually cross thresholds of harm. We often risk discovering the thresholds only after we breach them.
Some questions came to mind. What thresholds for human health might be crossed as more CO2 is added to the air? Could we anticipate the harm before it occurs? Could we utilize sustainability science to engage in preventive medicine/public health on a global scale? Then another recollection - CO2 stimulates involuntary breathing in mammals. Would we breathe more rapidly, or feel a little anxious at some higher level of CO2, or perhaps already?
(Photo Credits: Jake Paszko*)
I rose and searched for literature on CO2 and ventilation in humans. I felt a little vindicated upon learning that CO2 does indeed induce panic attacks, but (thankfully) at much higher concentrations than our current atmosphere contains. I’d welcome being wrong about lower-dose effects, but had they really been investigated? I created a file folder for CO2-and-health articles, and emailed my insights to some colleagues for perspective. A few days later I found a theoretical paper suggesting that lower levels of exposure, over the long term, could turn our blood acidic. Then came the treasure trove of studies on the effects of increased CO2 on crew members during space flights and submarine missions. CO2 became a project.
Various colleagues and students helped me learn about the relevant physiology and health concerns. I am grateful they supported a nascent idea. The topic had enough substance to pique Tyler’s interest. He fully pursued the challenges and helped to build a great team of colleagues to rigorously handle the breadth of what we were learning.
We learned that acute spikes in CO2 exposure occur indoors where our exhalations can build up. Some climate adaptations – more air-conditioning and time inside – exacerbate exposures, as do increasingly air-tight buildings with reduced ventilation designed for energy efficiency. Urban environments can trap CO2, creating a dome of increased exposure. As the background levels of CO2 increase, can we still buffer the acute exposures well? Do the spikes increase?
One of our co-authors, Reudi, studies physiological effects of low/high oxygen environments. We considered some experiments for assessing health effects of CO2. However, the major funding sources do not have direct health effects of CO2 in their funding priorities – it’s just not on their radar yet – so we saw the need for a review article to highlight this topic and galvanize some vital studies. Here it is!
* (Jake Paszko – a young photographer who enjoys capturing his travels through photographs. Born and raised outside of Chicago (Vernon Hills), Jake has recently traveled far from home – where he enjoys capturing the beauty of his travels and sharing it with friends back home.)