A UK doctor posted a Youtube video claiming that HEPA vacuum filter bags contain fiberglass. That claim has since been disputed by many.
Further, the UK doctor, Simon Freilich, has backed off his claims.
After some pushback from YouTube viewers saying the bags they’d checked didn’t have dangerous glass fibers in them, Freilich posted that he couldn’t research “every possible type” and that there “are clearly various types of filters and materials out on the market.”https://www.oregonlive.com/coronavirus/2020/04/is-it-safe-to-make-a-diy-mask-out-of-a-vacuum-bag-debate-erupts.html
Vacuum bag makers say they have never used fiberglass materials.
Many have to say “not suitable for any other uses” (or similar) due to liability concerns. If someone uses a product in a way that the manufacturer has not tested, the manufacturer does not wish to be accused of liability for any harm that may occur.
Freilich said he got his info from an unnamed random Youtube video – because, you know, social media is a highly reliable source of information.
Freilich has updated his own social media with this:
The unfortunate reality, having looked through the research, is that home made masks are only marginally better than no masks at all, and the effects are difficult to isolate as usually a range of measures are simultaneously enacted. Hence the best protection is to stay away from other people, as far as possible. Obviously, this is difficult for many but that’s literally the best method.
He acknowledged that he has no expertise in mask design or materials.
What happened: a social media post used the “appeal to authority” method of argument and then went viral and got picked up by the news media.
We tend to treat “facts” promoted by authorities, “experts”, celebrities and politicians as truth. As Bertrand Russell said (I’m paraphrasing): facts are true (or false) regardless of who says they are true or false. But most people fall for the “appeal to authority” argument which is why it is one of the top most used forms of persuasion. Russell viewed such arguments as the worst form of argument possible and insisted on facts and logic as the only valid forms of argument.
Once Doctor Freilich posted his video, his “assertion” became a “fact”. Once established as “fact” it is very difficult to undo the public perception of that topic. In this way, untrue “facts” become “true facts”, even though they are not true.