It seems to be human nature (confirmation bias) to expect to see something, and when you think you have seen it to stop looking.
I'm looking at the same documents presented en-masse by grey_whiskers and What I see is quite different. This is what I see: (each link in order from the first, followed by the key conclusions copied from the article and my translation of what that really means).
https://www.medrxiv.org/content/10.1101/2021.05.18.21257385v1.full
Mask mandate and use efficacy in state-level COVID-19 containment
Conclusions Mask mandates and use are not associated with slower state-level COVID-19 spread during COVID-19 growth surges. Containment requires future research and implementation of existing efficacious strategies.
Translation: Masks don't work to significantly reduce virus transmission. More research needed.
https://swprs.org/face-masks-evidence/
Are Face Masks Effective? The Evidence.
A) Studies on the effectiveness of face masks
So far, most studies found little to no evidence for the effectiveness of face masks in the general population, neither as personal protective equipment nor as a source control.
A May 2020 meta-study on pandemic influenza published by the US CDC found that face masks had no effect, neither as personal protective equipment nor as a source control. (Source)
A Danish randomized controlled trial with 6000 participants, published in the Annals of Internal Medicine in November 2020, found no statistically significant effect of high-quality medical face masks against SARS-CoV-2 infection in a community setting. (Source)
A large randomized controlled trial with close to 8000 participants, published in October 2020 in PLOS One, found that face masks “did not seem to be effective against laboratory-confirmed viral respiratory infections nor against clinical respiratory infection.” (Source)
A February 2021 review by the European CDC found no high-quality evidence supporting the effectiveness of non-medical and medical face masks in the community. Furthermore, the European CDC advised against the use of FFP2/N95 masks by the general public. (Source)
A July 2020 review by the Oxford Centre for Evidence-Based Medicine found that there is no evidence for the effectiveness of face masks against virus infection or transmission. (Source)
A November 2020 Cochrane review found that face masks did not reduce influenza-like illness (ILI) cases, neither in the general population nor in health care workers. (Source)
An April 2020 review by two US professors in respiratory and infectious disease from the University of Illinois concluded that face masks have no effect in everyday life, neither as self-protection nor to protect third parties (so-called source control). (Source)
An article in the New England Journal of Medicine from May 2020 came to the conclusion that face masks offer little to no protection in everyday life. (Source)
A 2015 study in the British Medical Journal BMJ Open found that cloth masks were penetrated by 97% of particles and may increase infection risk by retaining moisture or repeated use. (Source)
An August 2020 review by a German professor in virology, epidemiology and hygiene found that there is no evidence for the effectiveness of face masks and that the improper daily use of masks by the public may in fact lead to an increase in infections. (Source)
C) Effectiveness of N95/FFP2 mask mandates
In January 2021, the German state of Bavaria was one of the first places in the world to mandate N95/FFP2 masks in most public settings. A comparison with other German states, which required cloth or medical masks, indicates that even N95/FFP2 masks made no difference.
(AND THERE IS MUCH MORE RELATED TO DANGERS OF MASKS IN THIS LINK)
Translation: Masks don't work to significantly reduce virus transmission.
https://pubmed.ncbi.nlm.nih.gov/29395560/
[Effect of a surgical mask on six minute walking distance]
Results: Distance was not modified by the mask (P=0.99). Dyspnea variation was significantly higher with surgical mask (+5.6 vs. +4.6; P<0.001) and the difference was clinically relevant. No difference was found for the variation of other parameters.
Conclusion: Wearing a surgical mask modifies significantly and clinically dyspnea without influencing walked distance.
Translation: Even a simple surgical mask has a negative health impact on a healthy person when walking for 6 minutes.
https://pubmed.ncbi.nlm.nih.gov/32590322/
"Exercise with facemask; Are we handling a devil's sword?" - A physiological hypothesis
Exercising with facemasks may reduce available Oxygen and increase air trapping preventing substantial carbon dioxide exchange. The hypercapnic hypoxia may potentially increase acidic environment, cardiac overload, anaerobic metabolism and renal overload, which may substantially aggravate the underlying pathology of established chronic diseases. Further contrary to the earlier thought, no evidence exists to claim the facemasks during exercise offer additional protection from the droplet transfer of the virus. Hence, we recommend social distancing is better than facemasks during exercise and optimal utilization rather than exploitation of facemasks during exercise.
Translation: I personally experienced hypercapnic hypoxia (and nearly collapsed) after browsing 20 minutes in a grocery store wearing a simple surgical mask, and had to be helped outdoors and removing my mask. Even though I recovered quickly after removing the mask, this is very real for me. I now use an N95 ventilator with a battery powered filtered fan (available on Amazon and other places for around $50), which clears out the exhaled CO2 after each breath. With that, I can tolerate the mask for up to about 30 minutes
https://pubmed.ncbi.nlm.nih.gov/15340662/
The physiological impact of wearing an N95 mask during hemodialysis as a precaution against SARS in patients with end-stage renal disease
Conclusion: Wearing an N95 mask for 4 hours during HD significantly reduced PaO2 and increased respiratory adverse effects in ESRD patients.
Translation: That aint good, folks!
https://pubmed.ncbi.nlm.nih.gov/26579222/
Respiratory consequences of N95-type Mask usage in pregnant healthcare workers-a controlled clinical study
Conclusions: Breathing through N95 mask materials have been shown to impede gaseous exchange and impose an additional workload on the metabolic system of pregnant healthcare workers, and this needs to be taken into consideration in guidelines for respirator use. The benefits of using N95 mask to prevent serious emerging infectious diseases should be weighed against potential respiratory consequences associated with extended N95 respirator usage.
Translation: Wearing the mask may be more dangerous than Covid-19
(Note: I'll continue going through the rest of grey_whiskers links and post more later)