You are correct...from the article...

"This study ONLY looks at CO2 re-breathing toxicity."

As the authors write:

“other noxious agents in the masks contribute to toxicological long-term effects like the inhalation of synthetic microfibers, carcinogenic compounds and volatile organic compounds could also play a role regarding our research question”

You are correct...from the article...

"This study ONLY looks at CO2 re-breathing toxicity.

As the authors write:

“other noxious agents in the masks contribute to toxicological long-term effects like the inhalation of synthetic microfibers, carcinogenic compounds and volatile organic compounds could also play a role regarding our research question”