Henry has an understanding of elemental chemistry better than I. I felt he could digest the article separating the useful from what is not. I had to sift through pile of pharmaceutical propaganda selling fluoride laced "Alice in Wonderland" medicine... before I linked to this brief medical article(no ads; no politics). I was giving Henry a starting point as to his question, "Why?" He is a bright chap, as it seems you are. Both of you are well on your way to figuring this out.
I do find much of this mystifying.
Sold to innocents that may never see a toxic land fill... Yet, eat, drink, & wear toxic products it all day long.
As for me, well... let us leave it be said I am a humorist. Thank you for your interest in this matter. And furthering my education.
Disclaimer: Mark Twain (1835-1910-To be continued) is unlicensed. His river pilot's license went delinquent in 1862. Caution advised. Daily Paul ☑