[marchenko]

I think the poster has a good point. It's not just the one submariner study he's referencing that's relevant, it's the decades of experience navies of various nations have operating submarine fleets - the armed forces are not shy about collecting physiological data in the service of operational readiness. If the headline article is correct, we should be very concerned that a significant fraction of the world's nuclear weapons are immediately operated by officers experiencing extraordinary CO2 exposure. Every submariner is green at some point (and there are female submariners as well) - how is acclimation handled?

[maxbond]

I agree it's worth investigating. I just found it peculiar how unreceptive they were to the suggestion that the population was unrepresentative, yet how aware they were that the population was, in fact, unrepresentative.

The original suggestion, way up thread, was not to overgeneralize studies. This is a huge problem in our society.

[learc83]

I'm not unreceptive . It's entirely possible that fit militarily aged men under a certain height aren't as impacted by high C02 levels.

However I find it unlikely that they are completely immune to the effect at a dose 10x higher than what the people in the original Harvard study were exposed to.

As to whether long term exposure has a mitigating effect. That's possible, but if the effect is as great as the Harvard study shows, then the navy almost certainly would have noticed the impact on new submariners in the last 80 years.

Btw the original Harvard study was mostly college students, so it's hardly representative either.

Here's another study that shows no impact on military aged people who aren't submariners https://www.ncbi.nlm.nih.gov/pubmed/31240239.

And here's a study that showed no impact from an introduction of pure C02 (these weren't submariners either) https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12284?c...

And here's another one that shows no cognitive impact at 5,000ppm https://www.sciencedirect.com/science/article/abs/pii/S03601...

All the studies I've seen that do show an impact, aren't using just C02, they are more broadly studying poor ventilation--C02 is just one factor. Every study that isolates C02 level shows nothing. The most likely explanation is that if there is an impact on cognition from poor building ventilation, it's not the C02 doing it.

I researched this topic pretty thoroughly a while back. I was worried enough by the hype that I bought a C02 monitor, but after I researched it, I'm not concerned.

[mleonhard]

> Here's another study that shows no impact on military aged people who aren't submariners https://www.ncbi.nlm.nih.gov/pubmed/31240239

Those are prospective astronauts. I would expect them to be even more tolerant of CO2 and claustrophobia than submariners.

> And here's a study that showed no impact from an introduction of pure C02 (these weren't submariners either) https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12284?c....

> And here's another one that shows no cognitive impact at 5,000ppm https://www.sciencedirect.com/science/article/abs/pii/S03601....

These studies back up your claims. Thanks for sharing them. They were both done by the same people. Do you know if anyone else has tried to reproduce their results?

I would like to know the specific substances in exhalation that negatively affect humans. CO2 not being one of them would be good news.

[learc83]

>Those are prospective astronauts. I would expect them to be even more tolerant of CO2 and claustrophobia than submariners.

They weren't prospective astronauts, they were "astronaut like individuals". Men and women in their 30s and 40s with bachelor degrees and technical skills who can pass a modified flight physical (that from the description in the paper doesn't include any kind of C02 exposure).

Unlike submariners they aren't regularly exposed to 5,000ppm of C02, the height limit is much higher, and almost half of the participants were women.

They might be in better shape than the people in the Harvard experiment, because they screened out many medical conditions. But they are also lot older on average, and the exclusion criteria weren't particularly selective (140/90 bp for example).

Assuming good health has a protective effect you'd still expect so see some effect at 5x (5,000ppm) the level that showed an impact on the Harvard students.

[solveit]

The unrepresentativeness is irrelevant. It's quite conceivable that young fit men can take 20% more CO2 than the typical person before showing symptoms. 1000% is not, because it would have been noticed before and publicised as incredible. People have been on submarines for decades. You're telling me that, not only is there a hitherto unknown biological mechanism that renders young fit men practically immune to a toxic gas that debilitates the typical person at 0.1 times the dose and 0.01 times the exposure period, which is in itself a fantastic claim, but you're also telling me that this has not been noticed by any submariner in any country in decades! That nobody brought a fat politician aboard and noticed them keel over! That no old rich guy (perhaps... a famed movie director?) wanted to see the depths of the ocean! If you have priors on anything, it should be that this study is almost certainly wrong at a fundamental level. Quibbling about sample representativeness is a rounding error, which is why many people in this thread are well aware but completely uninterested in it.