Are Fibers From HEPA Filters Harmful to Health?

I have heard of people making diy face masks using hepa filters.  Personally, I thought that was a good idea, until I heard that fibers breaking off the filter could be breathed, and maybe cause respiratory problems. I put that out of mind until today, when I ran across this article while I was searching for something else. 

The conclusion at the end of the article is that the  fibers are no more harmful than other dust in the air.

Here is a link to the article.