A growing body of research indicates there are potentially large health benefits to improving indoor air quality. Indoor spaces are often poorly ventilated and expose occupants to high levels of contaminants, such as pathogens, particulates, and other pollutants. Because people spend nearly all their time indoors, improving indoor air quality would hugely benefit public health. (For more on the potential benefits of improving indoor air quality, see Juan Cambeiro and my recent
As the article says, submariners are more fit by standards of the general population, just by virtue of being in the military - but passing a PRT twice a year is no great feat, and the submarine community is notorious for fudging the PRT and letting sailors who fail it stay in anyway. Compared to most of the military, submariners are not that fit. Not that this invalidates your point, but still, thought it was funny.
The other thing is that being on a submarine you definitely do notice a cognitive decline that lifts when you open hatches, but that’s probably more from lower oxygen levels rather than higher CO2 levels. Not to mention lack of sleep and high stress.
I have a very high degree of confidence that we do not need more research on whether "high" ambient levels of CO2 affect cognition and I'm fairly sure I know where the disconnect is.
As background, at risk of being extremely too basic, all humans have a significantly higher amount of CO2 in their body and blood than is in the ambient air as a product of their metabolism. I suspect a big part of the reason people studying human physiology and people studying environmental effects of substances don't intuit one another's knowledge on this is that they are discussed in fundamentally different ways.
In physiology the amount of CO2 is discussed in terms of its partial pressure as a dissolved gas in one's blood. In the US we talk about dissolved blood gasses (mainly oxygen and carbon dioxide) using mmHg as units. Other countries often use SI units were the units are kPa. My medical training is American but I'll try and include kPas parenthetically. A normal partial pressure of CO2 in a healthy individual's blood is 40 mmHg +/- 5 (5.4 kPa +/- 0.7). In venous blood the amount of CO2 is slightly higher owing to this blood being the downstream recipient of metabolic products. The amount of CO2 in our blood (ie its partial pressure) is one of the most tightly regulated concentrations in our body and it is adjusted from moment to moment by our body subconsciously shifting our respiratory rate or the volume of our breaths.
Our body is able to adjust this so readily precisely because of a couple things alluded to in your piece. First, atmospheric/ambient CO2 is orders of magnitude lower than our physiologic CO2. Per Dalton's law we know the partial pressure of CO2 in well mixed atmospheric air at sea level is ~0.3 mmHg (0.04 kPa). Second, CO2 is a small nonpolar molecule that easily diffuses across the semipermiable membranes in our body (eg alveolar capillary endothelium, the blood brain barrier, and many others that are key to its many regulatory functions). Third, it's been shown across a variety of mammals and a variety of conditions that as the amount of CO2 rises in a subject's blood their minute ventilation (respiratory rate x tidal volume) will increase in order to maintain the blood CO2 concentration in a normal range. Fourth, in a number of disease states we know exactly how subjects appear and what the signs and symptoms of being unable to excrete enough CO2 to remain at a normal level.
The fourth point is largely tangential because it is well demontrated from the third point that mammal physiology (and humans in general) have a huge amount of respiratory reserve, which is to say we know that humans exercising can product many times the amount of CO2 that they do at rest but maintain their blood CO2 concentrations at baseline.
Since this has already gone on a long time I'll also point out this EPA study (https://www.epa.gov/sites/default/files/2015-06/documents/co2appendixb.pdf) showing that even at CO2 concentrations of 1% (10,300 ppm; which is to say, 25x atmospheric concentrations) the physiologic tolerance of this is indefinite though it induces physiologic changes which are predictable from what I wrote out above.
Given that our brain is continually exposed to CO2 levels approximately a hundred times higher than atmospheric CO2 and that its concentration is so tightly regulated with a lot of reserve it seems extremely unlikely that small (relative to the concentrations in the human body) increases in the ambient air would result in cognitive changes (it would also be easy to disprove CO2 as the causative agent in these analyses since we can easily test for the blood concentrations in humans to see if they are altered by the small [again, relatively speaking] changes in ambient CO2).
More specifically than "cognitive effects", aren't there decent studies that show that high CO2 levels make you sleepy? Testing specifically for sleepiness seems like it might be easier than testing for general cognitive impact, and it stands to reason that making yourself sleepier will be bad for your generic thinking as well.
"Schaefer (1961) reported that 23 crewmen exposed to CO2 at 15,000 ppm for 42 days in a submarine showed no psychomotor testing effects but showed moderate increases in anxiety, apathy, uncooperativeness, desire to leave, and sexual desire" - yeah, maybe that was the 42 days in the submarine? anyway this is a bit of a relief because I had the vague back of mind fear that rising CO2 concentrations would make us all dumber, and in fact the data looks like a classic "no real effect but if you cherry-pick and screw your eyes up right the Garden of Forking Paths will give you something publishable"
Maybe I'm reading too much into the noise, but the difference in shape of the data for crisis response - dense middle at 500, noisy but slight overall increase at 1000, lower 1500 - suggests some sort of cortisol fight-or-flight response to medium levels of CO2 that would hurt most cognition but benefit crisis reactions. I'd love to see experiments that track other biomarkers like cortisol to suggest a mechanism for reduced cognition and maybe specify what types of cognition.
As the article says, submariners are more fit by standards of the general population, just by virtue of being in the military - but passing a PRT twice a year is no great feat, and the submarine community is notorious for fudging the PRT and letting sailors who fail it stay in anyway. Compared to most of the military, submariners are not that fit. Not that this invalidates your point, but still, thought it was funny.
The other thing is that being on a submarine you definitely do notice a cognitive decline that lifts when you open hatches, but that’s probably more from lower oxygen levels rather than higher CO2 levels. Not to mention lack of sleep and high stress.
I have a very high degree of confidence that we do not need more research on whether "high" ambient levels of CO2 affect cognition and I'm fairly sure I know where the disconnect is.
As background, at risk of being extremely too basic, all humans have a significantly higher amount of CO2 in their body and blood than is in the ambient air as a product of their metabolism. I suspect a big part of the reason people studying human physiology and people studying environmental effects of substances don't intuit one another's knowledge on this is that they are discussed in fundamentally different ways.
In physiology the amount of CO2 is discussed in terms of its partial pressure as a dissolved gas in one's blood. In the US we talk about dissolved blood gasses (mainly oxygen and carbon dioxide) using mmHg as units. Other countries often use SI units were the units are kPa. My medical training is American but I'll try and include kPas parenthetically. A normal partial pressure of CO2 in a healthy individual's blood is 40 mmHg +/- 5 (5.4 kPa +/- 0.7). In venous blood the amount of CO2 is slightly higher owing to this blood being the downstream recipient of metabolic products. The amount of CO2 in our blood (ie its partial pressure) is one of the most tightly regulated concentrations in our body and it is adjusted from moment to moment by our body subconsciously shifting our respiratory rate or the volume of our breaths.
Our body is able to adjust this so readily precisely because of a couple things alluded to in your piece. First, atmospheric/ambient CO2 is orders of magnitude lower than our physiologic CO2. Per Dalton's law we know the partial pressure of CO2 in well mixed atmospheric air at sea level is ~0.3 mmHg (0.04 kPa). Second, CO2 is a small nonpolar molecule that easily diffuses across the semipermiable membranes in our body (eg alveolar capillary endothelium, the blood brain barrier, and many others that are key to its many regulatory functions). Third, it's been shown across a variety of mammals and a variety of conditions that as the amount of CO2 rises in a subject's blood their minute ventilation (respiratory rate x tidal volume) will increase in order to maintain the blood CO2 concentration in a normal range. Fourth, in a number of disease states we know exactly how subjects appear and what the signs and symptoms of being unable to excrete enough CO2 to remain at a normal level.
The fourth point is largely tangential because it is well demontrated from the third point that mammal physiology (and humans in general) have a huge amount of respiratory reserve, which is to say we know that humans exercising can product many times the amount of CO2 that they do at rest but maintain their blood CO2 concentrations at baseline.
Since this has already gone on a long time I'll also point out this EPA study (https://www.epa.gov/sites/default/files/2015-06/documents/co2appendixb.pdf) showing that even at CO2 concentrations of 1% (10,300 ppm; which is to say, 25x atmospheric concentrations) the physiologic tolerance of this is indefinite though it induces physiologic changes which are predictable from what I wrote out above.
Given that our brain is continually exposed to CO2 levels approximately a hundred times higher than atmospheric CO2 and that its concentration is so tightly regulated with a lot of reserve it seems extremely unlikely that small (relative to the concentrations in the human body) increases in the ambient air would result in cognitive changes (it would also be easy to disprove CO2 as the causative agent in these analyses since we can easily test for the blood concentrations in humans to see if they are altered by the small [again, relatively speaking] changes in ambient CO2).
And what are the cognitive affects on children wearing face masks in a classroom? Any tests on CO2 levels under a face mask?
More specifically than "cognitive effects", aren't there decent studies that show that high CO2 levels make you sleepy? Testing specifically for sleepiness seems like it might be easier than testing for general cognitive impact, and it stands to reason that making yourself sleepier will be bad for your generic thinking as well.
Interesting and balanced
"Schaefer (1961) reported that 23 crewmen exposed to CO2 at 15,000 ppm for 42 days in a submarine showed no psychomotor testing effects but showed moderate increases in anxiety, apathy, uncooperativeness, desire to leave, and sexual desire" - yeah, maybe that was the 42 days in the submarine? anyway this is a bit of a relief because I had the vague back of mind fear that rising CO2 concentrations would make us all dumber, and in fact the data looks like a classic "no real effect but if you cherry-pick and screw your eyes up right the Garden of Forking Paths will give you something publishable"
Maybe I'm reading too much into the noise, but the difference in shape of the data for crisis response - dense middle at 500, noisy but slight overall increase at 1000, lower 1500 - suggests some sort of cortisol fight-or-flight response to medium levels of CO2 that would hurt most cognition but benefit crisis reactions. I'd love to see experiments that track other biomarkers like cortisol to suggest a mechanism for reduced cognition and maybe specify what types of cognition.
Seems like the mixed evidence of impact of GHG on global warming.