It is odd, isn't it? The effect sizes seem ridiculous*, but there's nothing obviously wrong with that study (aside from the sample size). Cochran has blogged about oxygen before as well. To compile some of the relevant papers:
The problem for me is that while it makes sense that since we run on oxygen and the brain uses a lot of oxygen (the whole 'BOLD' thing etc), more oxygen might be better, it has the same issue as Kurzban's blood-glucose/willpower criticism: if the brain needs more oxygen than it's getting, why doesn't one simply breath a little more? While sedentary during these sorts of tasks, you have far more breathing capacity than you should need - you are able to sprint all-out without falling over of asphyxiation, after all. So there's no obvious reason there should be any lack, even more so than for glucose. And shouldn't CO2 levels closely track various aspects of weather? But as far as I know, various attempts to correlate weather and cognitive performance or mood have turned up only tiny effects. In addition, too much oxygen can be bad. So is it too little oxygen or too much nitrogen or too much carbon dioxide...?
Jessica Taylor for lending me a CO2 monitor so that I could see variability in indoor CO2 levels.
What monitor is that? You could try recording CO2 long-term, especially if it's a data logger. Opening windows is something that's easily randomized.
I did some looking and compiling of consumer-oriented devices a while ago: https://forum.quantifiedself.com/t/indoor-air-quality-monitoring-health/799/40 I was not too impressed since nothing hit the sweet spot of accurate CO2 and PPM measurement under $100. The Netatmo looked decent but there are a lot of complaints about accuracy & reliability (checking the most recent Amazon reviews, still a lot of complaints).
I've been thinking maybe I should settle for the Netatmo. I've been working on a structural equation model (SEM) integrating ~100 personal data variables to try to model my productivity (some current sample output), and it would be nice to have even noisy daily C02 variables (as long as I know how noisy and can use it as a latent variable to deal with the measurement error). Correlation-wise, I think backwards causation can be mostly ruled out, and the most obvious confound is weather, which is already in my SEM.
* taken at face value, with reasonable estimates of how much rooms differ from day to day or week to week, CO2 levels would explain a lot or maybe most of variability in IQ tests or cognitive performance!
OK, this literature review wins the $500. If you want to PM me with a payment mechanism it's yours (I'll follow-up if you don't).
If you want to state your reservation price for the certificate I might be willing to buy it, but I expect we won't be able to make that work out.
I would likely subsidize the inclusion of CO2 data in your personal monitoring, if you commit to publishing the relevant data and if you aren't going to monitor CO2 anyway.
OK, this literature review wins the $500. If you want to PM me with a payment mechanism it's yours (I'll follow-up if you don't).
Far be it from me to turn down free money. You can send it in Bitcoin to 1CkXM7sGSgMPKJ6RnpeaNDHyvVEzCHq2rY or via Paypal to gwern0@gmail.com. If neither of those works for you, email me with what would.
I am probably going to get a Netatmo. On closer inspection the Foobot is not as impressive as I thought as it does not have a CO2 sensor.
EDIT: thanks. I've ordered a Netatmo. EDITEDIT: arrived and configured. Seems to work.
Example data export: https://dl.dropboxusercontent.com/u/85192141/2016-06-23-netatmo.csv I am currently running a CO2/sleep experiment after noting alarmingly high CO2 levels in the morning.
Some followup links:
Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, National Research Council (2007), chapter 3 "Carbon Dioxide"; many negative mental and physical effects at extremely high CO2 concentrations >50000PPM; consistent statistically-significant effects below that tend to be harder to find but from the descriptions, they often were not using sensitive tests of higher cognitive functioning, a broad array of different measurements, and very small sample sizes; I suspect a meta-analysis grouping tasks by domain with some correction for ceiling effects might turn in a very different conclusion than their fairly sanguine conclusion that there are no cognitive impairments <40000PPM and <25000PPM is a perfectly safe limit. (Oddly enough, I came across this book on an anti-global-warming site; apparently Satish et al 2012 is really just global warming propaganda scare tactics, because the Navy has proven that CO2 is perfectly safe.) Cited for cognitive effects:
- Brown, E.W. 1930. "The physiological effects of high concentrations of carbon dioxide". U.S. Naval Med. Bull. 28:721-934 (as cited in NRC 1996).
- Consolazio, W.B., M.B. Fisher, N. Pace, L.J. Pecora, and A.R. Behnke. 1947. "Effects on man of high concentration of carbon dioxide in relation to various oxygen pressures during exposures as long as 72 hours". Am. J. Physiol. 151:479-503 (as cited in NRC 1996).
- Gellhorn, E., and I. Spiesman. 1934. "Influence of variations of O2 and CO2 tension in inspired air upon hearing". Proc. Soc. Exp. Biol. Med. 32:46-47.
- Gellhorn, E., and I. Spiesman. 1935. "Influence of hypercapnea and of variations of O2- and CO2-tension in inspired air upon hearing". Am. J. Physiol. 112:519-528 (as cited in NRC 1996)
- Glatte, Jr., H.A., G.J. Motsay, and B.E. Welch. 1967. "Carbon Dioxide Tolerance Studies". Rep. No. SAM-TR-67-77. Aerospace Medical Division, USAF School of Aerospace Medicine, Brooks Air Force Base, San Antonio, TX (as cited in NRC 1996).
- Menn, S.J., R.D. Sinclair, and B.E. Welch. 1970. "Effect of inspired pCO2 up to 30 mm Hg on response of normal man to exercise". J. Appl. Physiol. 28(5):663-671 (as cited in NRC 1996).
- Radziszewski, E., L. Giacomoni, and R. Guillerm. 1988. "Effets physiologiques chez l’homme du confinement du longue duree en atmosphere enrichie en dioxyde de carbone". Pp. 19-23 in Proceedings of the Colloquium on Space and Sea [in French]. European Space Agency, Brussels, Belgium (as cited in NRC 1996).
- Schaefer, K.E. 1961. "A concept of triple tolerance limits based on chronic carbon dioxide toxicity studies". Aeromed. Acta. 32:197-204.
- Schneider, E.C., and D. Truesdale. 1922. "The effects on the circulation and respiration of a increase in carbon dioxide content of the blood in man". Am. J. Physiol. 63:155-175 (as cited in NRC 1996).
- Sinclair, R.D., J.M. Clark, and B.E. Welch. 1969. "Carbon dioxide tolerance levels for space cabins". Proceedings of the Fifth Annual Conference on Atmospheric Contamination in Confined Spaces, September 16-18, Wright-Patterson Air Force Base, Dayton, OH.
- Sinclair, R.D., J.M. Clark, and B.E. Welch. 1971. "Comparison of physiological responses of normal man to exercise in air and in acute and chronic hypercapnia". Pp. 409-417 in Underwater Physiology, C.J. Lambertsen, ed. New York: Academic Press. [can download book from Libgen if Google Books link doesn't work]
- Storm, W.F., and C.L. Giannetta. 1974. "Effects of hypercapnia and bedrest on psychomotor performance". Aerosp. Med. 45(4):431-433.
- Sun, M., C. Sun, and Y. Yang. 1996. "Effect of low-concentration CO2 on stereoacuity and energy expenditure". Aviat. Space Environ. Med. 67(1):34-39.
- Wamsley, J.R., E.W. Youngling, and W.F. Behm. 1969. "High fidelity simulations in the evaluation of environmental stress: Acute CO2 exposure". Aerospace Med. 40:1336-1340 (as cited in NRC 1996).
- Yang, Y., S. Changnian, and M. Sun. 1997. "The effect of moderately increased CO2 concentration on perception of coherent motion". Aviat. Space Environ. Med. 68(3):187-19.1
More:
Sleep oriented studies:
A new one: "Using EEG to characterise drowsiness during short duration exposure to elevated indoor Carbon Dioxide concentrations", Snow et al 2018:
Drowsiness which can affect work performance, is often elicited through self-reporting. This paper demonstrates the potential to use EEG to objectively quantify changes to drowsiness due to poor indoor air quality. Continuous EEG data was recorded from 23 treatment group participants subject to artificially raised indoor CO2 concentrations (average 2,700 ± 300 ppm) for approximately 10 minutes and 13 control group participants subject to the same protocol without additional CO2 (average 830 ± 70 ppm). EEG data were analysed for markers of drowsiness according neurophysiological methods at three stages of the experiment, Baseline, High CO2 and Post-Ventilation. Treatment group participants’ EEG data yielded a closer approximation to drowsiness than that of control group participants during the High CO2 condition, despite no significant group differences in self-reported sleepiness. Future work is required to determine the persistence of these changes to EEG over longer exposures and to better isolate the specific effect of CO2 on drowsiness compared to other environmental or physiological factors.
Some recent kerfluffles over CO2 (prompted by people rediscovering Allen et al 2016 on Twitter etc) lead me to one I missed: "Breathing Carbon Dioxide (4% for 1-Hour) Slows Response Selection, Not Stimulus Encoding", Vercruyssen 2014. 4% is a ton but the results remain subtle, at best.
I see. But they do have a data-logging version which is only another $40. (Although at that price, since it's only recording CO2, humidity, and temperature according to the data sheet, one might want to buy one of the other air quality sensors I listed in the QS thread; but on the gripping hand, those have persistent controversies about how accurate they really are, and you would hope that a C02 specialty site like this would be selling more accurate sensors.)
And shouldn't CO2 levels closely track various aspects of weather?
Shoud they? Weather is basically temperature + precipitation + wind + humidity. Off the top of my head I don't see any reasons why different weather should imply different CO2 concentrations.
Photosynthesis requires light to occur; weather affects the amount of light. Direction of wind determines the amount of upwind plants, and so on. Here's a link to a week's worth of data from an outdoor CO2 monitor in Utah; it looks to me like the difference is probably imperceptible, even if one buys the effect sizes for the 600 to 1000 ppm study.
Interesting... I expect the main drivers to be the seasonal cycle (outside of the tropics) and the diurnal cycle.
Here is a nice animation of the seasonal cycle which also demonstrates the asymmetry of the Northern and Southern hemispheres...
I was actually thinking more along the lines of opening windows; you only want your windows open in a fairly narrow band of temperatures, and things like precipitation would also encourage people to seal their houses or apartments or offices up and presumably increase carbon dioxide levels. But yeah, there are probably direct effects from light levels and barometric pressure and other things.
Weather clearly affects people in a lot of ways, do disentangling the CO2 effects will be hard.
Any idea how high will CO2 go in a room in a normal building, say during winter in a well-sealed residential house? Offices and apartments buildings typically have HVAC systems which have standards for air exchange and such, but a single-family house can do whatever it wants to, including turning itself into an airtight box in the name of energy efficiency...
Weather clearly affects people in a lot of ways, do disentangling the CO2 effects will be hard.
Weather affects people, but as I said, the effects generally seem to be small and not as large as the experiment claims. If there were large weather effects, they could be due to CO2 or other aspects of weather; but since there are not, that implies that all aspects of weather including CO2 are not that important. (Modus ponens, modus tollens, etc.)
the effects generally seem to be small
I don't know about that. Anecdotally, I know some people who say that how well they think/work/feel is noticeably -- to them -- affected by weather, mostly a combination of pressure and humidity. Also anecdotally, the older you get, the more sensitive to weather your body becomes.
Myself, I feel more energetic in high-pressure low-humidity weather than in low-pressure high-humidity, but I haven't tried to quantify it or be rigorous about it.
Anecdotally, I know some people who say that how well they think/work/feel is noticeably -- to them -- affected by weather, mostly a combination of pressure and humidity. Also anecdotally, the older you get, the more sensitive to weather your body becomes.
People think a lot of mistaken things about their personal psychology. But the weather correlations are still small: 'Does Life Seem Better on a Sunny Day? Examining the Association Between Daily Weather Conditions and Life Satisfaction Judgments', Lucas & Lawless 2013; 'Subjective wellbeing: why weather matters', Feddersen et al 2015. I found the same thing in my data so far. May just be setpoints.
But the weather correlations are still small
The attempt to find weather correlations universal to all humans seems misguided to me. Different people react to weather differently. I get more energy from high and dry, but there are people who get more energy from low and wet, and I know one girl who switched after being pregnant and giving birth. You take a group average and it will come to about zero, but that just masks individual reactions.
Using fixed-effects for each person helps model such heterogeneity, but still nothing comes out. I don't see why you would dismiss them so readily. It's just that the old-wives-tales are wrong yet again.
If you really believe that weather relationships could be so obscure and complicated and individual that there are no meaningful average effects, that casts a lot of doubt on the claim that there's a consistent average effect from CO2 and all the background studies about ventilation and air quality as well.
Using fixed-effects for each person helps model such heterogeneity, but still nothing comes out.
Feddersen et al model very particular heterogeneity, to wit the usual demographic and econometric data:
These include age and its square, the number of household dependents aged between 0 and 24 years, and the natural logarithm of nominal household disposable income for the previous financial year in Australian dollars. Dummy variables are also included for disability status, employment status, marital status and education. These controls are typically the most important determinants of self-reported life satisfaction
That's not going to help ferret out idiosyncratic reaction to weather.
It's just that the old-wives-tales are wrong yet again.
I don't have any old wives to listen to :-) The source is my personal experience and the experience of people I know who don't seem to have any reason to lie about it.
If you really believe that weather relationships could be so obscure and complicated and individual that there are no meaningful average effects
I didn't say that. I said that not seeing average effects does not rule out individual-level effects and that at the anecdotal level I do see these effects.
And there is no reason to generalise to everything. I am sure that "bad air" which is bad enough to produce consistent measurable average effects exists and is not very hard to construct or find.
It won't be hard if the effects are as large as claimed in the original study. And while we are looking for the total effect, adding more contributions of weather to cognitive performance should make it easier to detect an overall effect (even if each points in a random direction), but that hasn't been true for weather.
It won't be hard if the effects are as large as claimed in the original study.
The study shows minor effects at 1000 ppm and pronounced effects at 2500 ppm. I don't think changes in weather would drive your CO2 concentration to these levels.
And if you interpret the effect of weather as mostly open vs closed windows, there is a whole bunch of other factors in play like the balance of indoor and outdoor contaminants, etc.
I am sceptical of these results, anyway, they look too big. And the authors mention another study:
Researchers in Hungary have questioned this assumption (Kajtar et al. 2003, 2006). The authors reported that controlled human exposures to CO2 between 2,000 ppm and 5,000 ppm, with ventilation rates unchanged, had subtle adverse impacts on proofreading of text in some trials, but the brief reports in conference proceedings provided limited details.
which implied ("subtle") small effect size.
Why do you call the effects at 1000ppm minor? They are easily big enough to measure statistically with a realistic sample size for an observational study, even if the effect of weather on CO2 was only say a 5% change in P(windows open).
Opening my window moves CO2 levels in my room from around 1400 to around 400ppm.
I agree the results look too big.
I don't see how it can be about oxygen. In the paper I linked, I think they directly add relatively pure carbon dioxide. And the total concentration is 0.1%. So the concentration of oxygen in the air is not really changing.
The texas natural experiment seems like an especially convincing complement to the more artificial setting, thanks for pointing it out.
If you look into this I will leave open the offer to buy certificates after the prize. So far not many takers on the prize, this comment is currently in the lead based on the literature review, not sure if there will be takers closer to the cutoff.
(aside from the sample size)
The sample size is small, but given the effect size I don't think it even matters that much. The error seems like less than a factor of 2.
taken at face value, with reasonable estimates of how much rooms differ from day to day or week to week, CO2 levels would explain a lot or maybe most of variability in IQ tests or cognitive performance!
This looks right to me (well "a lot," I don't think "most"), I assume that something is wrong. An obvious possible culprit is their cognitive test.
I don't see how it can be about oxygen.
I believe the human breathing regulation mechanism (how frequently/deeply you breathe) is driven by CO2 concentrations. So manipulating the CO2 affects the breathing which determines how much oxygen is your body getting.
It's also unlikely to be about oxygen because oxygen levels that reach the brain in a healthy person depend almost entirely on the amount of saturated haemoglobin, which is 95-100% of Hb in someone without serious lung heart or haemoglobin defects. This means that variability in O2 availability is more dependent on one's iron level than breathing/air effects. (I disclaim that I haven't yet looked into literature about O2 chemistry and supply to the brain so may be wrong)
The CO2 hypothesis at least makes some sense because bloodstream CO2 levels vary a bit.
Gwern's evolutionary argument seems weak because we did not develop in ancestral environments where we could properly trap CO2 (our CO2 sensors mightn't need to be very sensitive), and for our ancestord it was at least somewhat more important to conserve energy from breathing and somewhat less important to be be so intelligent.
In the paper I linked, I think they directly add relatively pure carbon dioxide. And the total concentration is 0.1%. So the concentration of oxygen in the air is not really changing.
Can't you apply that argument to oxygen and nitrogen as well? If you are willing to believe that adding a small absolute amount of carbon dioxide can have large effects on the brain, then I don't see why you would not also be willing to believe that decreasing oxygen (a critical fuel for the brain's metabolism) by a small absolute amount might have large effects on the brain. Injecting CO2 as they do does control for air variables like mold and temperature and humidity, but I didn't see anything about also injecting oxygen and nitrogen to independently manipulate the air composition in all 9 possible ways to disentangle which it is. It could be that CO2 is inert, but by pushing out oxygen and reducing oxygen levels has effects; it could be that CO2 is inert but it's both oxygen and nitrogen, or CO2 is poisonous but is combining with lack of oxygen.
The texas natural experiment seems like an especially convincing complement to the more artificial setting, thanks for pointing it out.
I found it interesting that the anti-mold renovations had such large apparent effects compared to the ventilation and other renovations.
The sample size is small, but given the effect size I don't think it even matters that much. The error seems like less than a factor of 2.
Small study effects go beyond just sampling error, so they are untrustworthy.
The CO2 intervention is doubling the density of CO2, and decreasing the density of oxygen by < 1%.
Small proportional changes seem unlikely to drive big effects, unless there is some feedback mechanism that is keeping the level precisely balanced. But 1% changes in oxygen should be happening all over the place. It seems much more plausible for doubling the density of CO2 to have a direct effect.
Similarly, the nitrogen intervention is a significant proportional change.
Small proportional changes seem unlikely to drive big effects, unless there is some feedback mechanism that is keeping the level precisely balanced.
Such as in the body, dealing with tightly regulated and critical aspects of metabolism like oxygen consumption.
But 1% changes in oxygen should be happening all over the place.
Perhaps they are. You don't know the effect because the existing experiments do not vary or hold constant oxygen levels. All you see is the net average effect, without any sort of partitioning among causes.
You don't know the effect because the existing experiments do not vary or hold constant oxygen levels. All you see is the net average effect, without any sort of partitioning among causes.
Existing experiments do vary oxygen levels systematically, albeit usually unintentionally, by geography. Going up 100 meters from sea level gives you a 1% drop in oxygen pressure and density. If that was enough for a detectable effect on IQ, then even the 16% lower oxygen levels around Denver should leave Coloradans obviously handicapped. IIRC altitude sickness does show a strong effect on mental performance, but only at significantly lower air pressures still.
And they also vary CO2 levels systematically by geography as well; if that was enough for a detectable effect on IQ, then the lower CO2 levels around Denver should make the rest of us at lower altitudes, such as sea level, look obviously handicapped. If you believe the altitude point refutes effects of oxygen, then it must refute effects of carbon dioxide and nitrogen as well...
Which is part of my original point about implausible effect sizes: the causal effect is underidentified, but whether it's oxygen or CO2 or nitrogen, it is so large that we should be able to see its repercussions all over in things like the weather (or altitude, yes).
It seems possible (I know of no evidence for or against) that human bodies adapt slowly to differences in O2 and CO2 level. In that case, newcomers to Denver might be smarter or stupider for a while, but after (say) a few months they might be back to baseline, but short-term fluctuations (e.g., sitting for a few hours in an office with slightly depleted O2 and slightly raised O2) could still have detectable cognitive effects.
The magnitude of the variation isn't nearly the same in the O2 vs CO2 cases. "16% O2 reduction is lost in the noise" is devastating evidence against the theory "0.2% O2 reduction has significant cognitive effects", but "16% CO2 reduction is lost in the noise" is weaker evidence against the theory "66% and 300% CO2 increases have significant cognitive effects".
I'm not arguing with you about implausible effect sizes, though. We should especially see significant seasonal effects in every climate where people typically seal up buildings against the cold or the heat for months at a time.
Such as in the body, dealing with tightly regulated and critical aspects of metabolism like oxygen consumption.
I meant, changing a level by 1% probably won't have a huge effect (e.g. 1/2 of a standard deviation) unless that level is itself controlled by a homeostatic process (or else has almost no variation).
You may have come across the NASA clean air study and this 4 minute TED talk by Kamal Meattle, an Indian businessman and environmental activist. Short version: you need 4 Areca Palm plants per person to convert CO2 to O2 during the day, 6-8 snake plants per person to convert CO2 to O2 during the night, and then a devil's ivy to remove other chemicals from the air. He rattles off a list of measured impacts for working in an office building with an appropriate number of plants that also seem pretty convincing.
It's not clear why he didn't go with the ones that looked best on the NASA study, the Peace Lily (also recommended by Nicholas Angel) or the Chrysanthemum (also recommended by the Emperor of Japan). But this also the first place where I saw someone discussing the relevant conversion rate (i.e. three plants per person wouldn't be enough); the NASA study synopsis on Wikipedia, at least, only mentions number of plants per area and doesn't seem to take the leaf surface area of the plant into consideration. So one suspects he's taken cost and efficiency into account.
Curious, as this comment inspired me to go get a Peace Lily for my desk.
I work in an office, but sit by myself (nearest person is maybe 8 meters or so away from me). The plant sits maybe 10 centimeters away on my left.
Did Meattle focus specifically on those office environments where people sit closely together?
I mean, I will reap benefits from having the plant regardless, but now I wonder how much I benefit vs. getting more plants (which is doable).
I just wanted to say thank you for for including the links to the TED talk and other actionable info (i.e. which plants to buy and how many per person). I have a tendency to see things like the main post and go "oh, that's interesting," but then never really follow-up on them, but knowing that I have a list of which plants to buy was enough additional motivation to make me take the issue more seriously. I'm intending to do a bit more research and get a air quality monitor in the next few days.
Since you mentioned other plants, I am wondering if there are places to look to consider the different plant options. My wife said she "didn't want ugly plants" (if possible), and I was also wondering if there were options I could look at that would be easier to care for (I live in the northern US, so I expect there may be >10week periods where taking a plant outside would be impracticable, not to mention unpleasant since we live in a large apartment building).
Unfortunately, that's the limit of my knowledge. If you do find something useful, please let us know.
So you ask any granny whether she thinks your head works better in fresh air rather than in a stuffy room, and she'll look at you like you're an idiot and point out that yes, of course it does, and do people these days know anything? X-)
If this is true, it could explain part of the apparent advantage the Bay Area has in technological innovation. Because of the moderate climate, it's more reasonable in that region to keep your windows open all the time. In Boston, we have to keep the windows closed for half the year because it's cold outside.
I like the idea of buying certificates of impact in this way... I wonder if you could scale this sort of thing with some kind of market platform.
Also, I've wondered about this multiple times before, but your post has finally nudged me into buying myself a CO2 monitor. The chance, even a modest chance, that I'm impairing my cognition, far outweighs the $130 and the possibility that I might have to open a window.
One or two research groups have published work on carbon dioxide and cognition. The state of the published literature is confusing.
Here is one paper on the topic. The authors investigate a proprietary cognitive benchmark, and experimentally manipulate carbon dioxide levels (without affecting other measures of air quality). They find implausibly large effects from increased carbon dioxide concentrations.
If the reported effects are real and the suggested interpretation is correct, I think it would be a big deal. To put this in perspective, carbon dioxide concentrations in my room vary between 500 and 1500 ppm depending on whether I open the windows. The experiment reports on cognitive effects for moving from 600 and 1000 ppm, and finds significant effects compared to interindividual differences.
I haven't spent much time looking into this (maybe 30 minutes, and another 30 minutes to write this post). I expect that if we spent some time looking into indoor CO2 we could have a much better sense of what was going on, by some combination of better literature review, discussion with experts, looking into the benchmark they used, and just generally thinking about it.
So, here's a proposal:
Some clarifications:
(Thanks to Andrew Critch for mentioning these results to me and Jessica Taylor for lending me a CO2 monitor so that I could see variability in indoor CO2 levels. I apologize for deliberately not doing my homework on this post.)