Possible toxicity of chronic CO2 exposure associated with face mask use | Hacker News Reader

Possible toxicity of chronic CO2 exposure associated with face mask use

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91 pointsandrenth54 comments

Despite the obviously charged assertion the authors make, I believe this is a good topic to discuss now that the weight of the pandemic is complete. You don't change emergency management plans in the middle of an emergency. We can and should question our approaches, extracting global principles that can be used next time this happens. Similar topics we should rigorously evaluate include FDA and CDC policies, but those are outside scope of the article.

I respect the authors' asking the question, but think their narrative is a bit weak / not tied down sufficiently to make a strong claim based solely on literature review.

For example: they raise the question of increases in stillborn births and then cite a 3X increase in stillbirths among studied women versus the population rate. Without additional facts, that looks potentially damning to mask wearing during a pandemic driven by a respiratory virus. What is less clear is how the accounting for observed versus actual is performed. Similar to crime statistics, the count of incidence is biased by several positive and negative factors, and stillbirths are not always captured. What _was_ observed was a significant increase in stillbirths due to COVID-19 (especially the Delta variant, which to be fair the authors mention).

An essentially no-risk intervention plausibly reduces infection risk and all of a sudden the bar of evidence to practice basic hygiene ratchets up to randomized phase 3 studies. Meanwhile, the same people will cite this preclinical, speculative, provocation of a paper and say masking is murder. Look at Japan’s experience with COVID. Look at the United States. That’s epidemiological data. Look at how elastomeric masks reduced TB infection rates to nil at the Texas Center for Infectious Disease. Masks (of any type) don’t work? That’s a political slogan, not evidence.

Someone can correct me, but is this paper really making the claim that wearing masks a contributing factor to stillbirth rates in Asia?

>Other cultures have been wearing face masks long before COVID [[157]]. The prepandemic face mask wearing habits of such countries are not comparable to the pandemic face mask wearing requirements, but scientific data supports our hypotheses from sections 4.1. and. 4.2. Even before the pandemic, in Asia the stillbirth rates have been significantly higher compared to e.g. Eurasia, Oceania or North Africa

Also, the authors don't explain how pre-pandemic mask wearing is different than pandemic mask wearing.

> Also, the authors don't explain how pre-pandemic mask wearing is different than pandemic mask wearing.

Frequency and duration are one difference. My understanding is that pre-pandemic Asian mask wearing is generally limited to the time a person was ill, not months at a time for 8+ hours a day.

The toxicity of chronic exposure to elevated CO2 levels has long been a topic of interest related to climate change for the reason that we could plausibly reach levels of clinical significance over the next 100 years. Interesting to see it arise in a different context.

The CO2 levels in masks are much higher than in outside air. Even if CO2 in our air has risen from around 280 ppm to 440 ppm since the pre-industrial times, CO2 concentrations in masks are at least one order of magnitude higher.

My CO2 meter maxes out at 5000 ppm pretty quickly in an N95 mask. Studies show the CO2 concentration after an hour of N95 face mask wear can be significantly above 8000 ppm, even as high as 30000 ppm [0][1].

People wearing these masks for many hours a day are likely the best in vivo examples of what increased CO2 concentrations in air does to a person. Until recently, we used to think that even such high concentrations did nothing. [2]

Still, I do feel the impact on my focus and mental clarity when CO2 is above 2000 ppm. Not N=1 as other people speak about noticing the same when they buy air quality monitors, even on HN. It feels intuitive that chronic exposure would decrease our mental sharpness, if not through permanent damage, then at least through the immediate, direct effects. They would, however, be ongoing if the atmospheric CO2 rose significantly and permanently.

[0] https://www.researchgate.net/figure/Average-CO2-levels-betwe...

[1] posted article

[2] https://pubmed.ncbi.nlm.nih.gov/20420727/

Masks are a small volume though. Wouldn't you need to be breathing shallowly or otherwise have compromised lung capacity to make a noticeable difference?

Seems like blood-oxygen levels would be a better proxy for the effects than CO2 levels inside most masks.

Hmm, yes, that's an important factor.

Let's say the average CO2 concentration in a mask is 19000 ppm (mid-point of 8000 ppm and 30000 ppm). If only 5% of the air inhaled by volume is from the mask and 95% is from outside air (440 ppm), then the average CO2 content of that inhaled air would be around 1350 ppm. I would say that's at the limits where CO2 starts to affect our mental acuity.

If 95% of the air is typical office air (at about 900 ppm), then the inhaled air would be at about 1800 ppm. That is where most people would probably feel the high CO2 concentration if they knew the feeling.

If the 5:95 split is correct, it would seem that wearing a mask could increase the inhaled air CO2 content by around 2-3x. It could be more or less depending on some factors. But in orders of magnitude, it would seem closer to 2.5x than 25x or 250x.

This lines up with my experience. Maybe the air in an N95 mask I would wear for several hours indoors would feel even worse than 1800 ppm. But there are many factors to how inhaled air feels, including temperature and humidity. So I'm happy with 1800 ppm as an estimate.

Someone should build real experiment for this and get some hard numbers. It could be a topic for a nice and times-relevant publication in respiratory health or for someone in general practice.

Yeah and it is largely ignored. It's developmental problems in high c02 atmosphere that really scares me. Adults handle temporary or even extended exposure well, but we don't have studies about extended c02 for kids, and there are no ways to ethically get them.

I really want a CO2 scrubber for my house. Ideally, it'd fix the CO2 into biologically inert carbon bricks that I would dump in household waste, or some other convenient long-term storage. Given how well solar panels have taken off, I suspect this is more likely to actually work than industrial scale carbon capture.

For one thing, houses have highly concentrated CO2 levels vs. the atmosphere. For another, there are a dozen simple carbon capture technologies in development that would work fine at house scale, but all are perpetually 5-10 years from reaching industrial scale.

Since I'm talking about a luxury good, it could follow the Tesla model of using wealthy early adopters to subsidize the development of more efficient products down the line.

Do you claim to know that current CO2 levels aren't causing human disease?

> Nor is it the first time the authors of the review have claimed face masks could have harmful effects. Several of the authors speculated in [OP ARTICLE] that masks might have caused stillbirths and other health issues. But this was an extrapolation based on studies exposing animals to carbon dioxide — and ignored the fact that masks don’t increase levels of the gas in humans in any clinically meaningful way. The Daily Mail nevertheless covered the paper in a story with an alarming headline, screenshots of which have been widely shared on social media.

https://www.factcheck.org/2023/04/scicheck-masking-has-minim...

[EDIT: I was wrong -- the fact check also explictly references the article being discussed here]

This is about a different article, right? Fact check is on https://doi.org/10.3389/fpubh.2023.1125150 but the article we're discussing here is https://doi.org/10.1016/j.heliyon.2023.e14117

> This is about a different article, right?

"Several of the authors speculated in a review published in March..."

is referring to this article.

Ah, you are correct, sorry about that.

I shouldn't try to follow this stuff on a phone...

I've made my comment a little clearer, thanks

I had a more thoughtful and charitable post written up, but I reconsidered. What I have instead now is: if you're gonna say not even medical staff like surgeons should wear masks and that they're responsible for millions of stillbirths, you gotta do better than a survey of iffy CO2 levels under mask experiments and some hysterics about submarine CO2 levels. You need to measure blood levels. Like, if I were a researcher who wanted to get onto conservative media, this is the paper I'd write.

The whole publication is a joke. It goes on and on about breathing "2.8–3.2% carbon dioxide" when mask dead space constitutes maybe 15-30% of human tidal volume. At rest.

And I'm pretty sure "2.8-3.2%" is a cherrypicked datapoint, other studies report lower concentrations.

Realistically, all of this is less of an issue than classroom CO2 exposure over a schoolday but nobody's acting outraged about that one for some reason.

One of the things I wonder about is the microplastic fibers ending up in our lungs.

Sure, medical professionals have been wearing them for years. But they haven't been reusing the same mask for days, crumpled up in pockets and disintegrated to the point of getting fluffy.

I wonder what that will do for long-term health effects. But I guess at that time there was no time to factor that in as any results of long term research would have come after the pandemic anyway.

I mean, if this is true, we have to quickly prevent gas stove as well as gas and oil heating to be added to home units. We also have to say to women to avoid barbecue afternoon when pregnant.

Maybe you're joking, but the bbq is acute exposure and the article focuses on chronic exposure. As for heating, if your heater puts your indoor CO2 above 0.5% then you are above the NIOSH / OSHA limits and should get it fixed. Article says measurements inside masks read 1 to 3%. Incidentally, bad indoor ventilation is an increasingly recognized health risk.

What, up to 3%? i missed that, but if true, that's a huge issue. Some woodworkers use way more airtight masks 4 to 8 hours a day, 5 days a week. If true, those concentration levels are criminal and I expect a lot of construction companies (and sawmills, and papermills) to get sued for damage.

You missed it? See the first sentence of the results section, table 1, and ... the rest of the paper.

I looked into some of the refs in table 1 and it seems they are being misrepresented, mostly because Kisielinski et al are acting like this is the concentration during inhalation when in the 2 papers I looked at it was average over time. Since exhaled breath has several percent, I think you really need to be able to resolve concentration over time and look at the inhale, otherwise the data is useless.

Woodworking masks have exhalation valves.

3% CO2 from mask wearing? I doubt it. I recently needed to measure 5% CO2, and I had to hold my breath to near-passout levels to reach 5% on the monitor. There’s no way that I could tolerate 3% for any length of time.

More likely these authors cherry-picked studies with typos in them.

Seems like the key thing would be to measure the concentration under mask during inhaling vs exhaling. Exhaled breath has many % CO2. The article references a whole table of articles measuring CO2 under masks. I haven't taken the time to check if they separate exhale vs inhale but would be curious to know.

Just thinking about the numbers. Exhaled air has 4% CO2, while fresh air has 0.04%. But if you inhale air with 3% CO2 that should add to those 4% yielding 7% exhale.

Now, in order to get 3% CO2 in your inhale this would mean that you would have to breathe in 42% stale air (with 7% CO2) mixed with 58% fresh air (~0 CO2).

I wonder if this 42-58 mix is plausible.

That would mean that the volume of gas trapped in a mask is 42% of lung capacity? Seems extremely implausible to me.

A typical breath is much less than full lung capacity, but even then I don't think it adds up.

I checked Roberge et al 2010 and it seems they don't separate inhalation from exhalation in the gas measurements under the mask.

I checked Sinkule et al 2012 and it's quite hard to tell how the review got those numbers from that paper.

Might check more when I have time later.

Since the volume of gas trapped by a mask is miniscule compared to the lungs, I wonder if it even matters. Might be better to just try to measure blood concentrations.

Yeah I was surprised they didn't measure blood concentrations--feels like the actual metric we should care about. I remember like, a lot of mic-drop social media posts about people being like "I wore a mask for 16 straight hours and my spo2 is 100% (or whatever), quit whining"

Yep, at 0.1-0.2% (1000-2000ppm) people start to get drowsy. at 0.2-0.5% (2000-5000ppm) people get heachaches, poor concentration, elevated heart rates, etc. It's quite unpleasant. 3% is 30,000 ppm.

While wearing a mask isn't fun, I've never experienced anything to that level while wearing mine.

Not buying it either.

I'd caution you against this idea that you can "know the feeling" of acute CO2 exposure.

For my PhD work (gas geochemistry) I spent hundreds of hours working in volcanic ice caves with CO2 levels up to 2% (we measured up to 3% but had a rule against being in above 2%). I always had a gas monitor with me so it was interesting to try and guess the levels. Neither I, nor anyone I was with, could guess reliably.

More than once I was with others in a cave, and they would freak out and say they felt high CO2 and we'd check the readings and nope. I actually think people (including myself) were responding to high humidity and heat and misinterpreting it as high CO2.

Of course, high CO2 is dangerous, all I'm saying is that it's surprisingly hard to disentangle it from all the other factors affecting how well your feel as a human, when you actually test yourself.

I'm reasonably certain I notice levels above 800ppm. It's subtle, but everyone in the house starts getting a little edgy (kids and adults). Sure enough, the CO2 meter is reporting > 800.

I doubt I could differentiate between 800 and 1600 though.

I'm not saying you're wrong, but remember 1600 ppm is only 0.16%, so that's impressive sensitivity. 4x atmospheric.

We've been discussing 1% to 3%, which is 10,000 to 30,000ppm.

In the early days of COVID, before we knew anything, I would go for runs outside and wear a mask (N95). I live in a densely populated city so this seemed like the appropriate thing to do.

While it was not pleasant, at no point did I start having issues you described so I have trouble buying the original claim.

There is a possible negative impact risk by imposing extended mask mandates especially for vulnerable subgroups. Circumstantial evidence exists that extended mask use may be related to current observations of stillbirths and to reduced verbal motor and overall cognitive performance in children born during the pandemic. A need exists to reconsider mask mandates.

Even with no mandate, masks alongside other factors, helped reduce COVID infection rates and mortality in Japan [1]. Meanwhile, this article is grasping for a mechanism of toxicity when no epidemiological evidence of toxicity exists, and masks are used occupationally by millions of workers daily.

There is evidence from a dedicated infectious disease hospital that elastomeric masks prevent transmission of illness:

—In a dedicated TB hospital, they have used elastomeric half-face respirators with N95 filter cartridges since 1995. The filters only need to be changed once per year.

—Before implementing these filters, they only used surgical masks that resulted in up to 50% of their staff becoming TST positive and 1-2% with TB disease.

—Since they started using the half-face respirators, they have not had a single TST conversion.

With a plausible mechanism (filtration), no evidence of harm, and some evidence of benefit with certain forms of masking, maybe what is really needed is a risk:benefit calculation. An essentially no-risk intervention plausibly reduces infection risk and all of a sudden the bar of evidence to practice basic hygiene ratchets up to randomized phase 3 studies. Meanwhile, the same people will cite this preclinical, speculative, provocation of a paper and say masking is murder.

Maybe there is something deeper behind this? People don’t like government mandates and don’t want to be told what to do in general. Individualism in contrast with the collectivist self-perception that is more pervasive in Japan may be a more important factor than evidence here. This observation will anger people because they want to believe their decisions are based on evidence, when they are really driven by psychology.

[1] https://www.medscape.com/viewarticle/982234

[2] https://nap.nationalacademies.org/catalog/25275/reusable-ela... (pages 106 to 107)

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