Sodium fluoride is one of them. In its natural state, fluorine is an essential trace mineral present in bones and teeth, where it helps calcium make these tissues hard. That is 'calcium fluoride' and is most often found naturally occurring in well water. What is added to municipal drinking waters is 'sodium fluoride,' which is quite different from the natural calcium fluoride. You can fill a library with the literature from around the world about the negative effects of sodium fluoride.
Sodium fluoride is a vitamin inhibitor.
It is an enzyme inhibitor. It can destroy the catalysts that make vitamins work. Explanations and sources for the above statements follow in the book. I am a student at Sierra High School, so I know firsthand how these practices can affect the students and teachers. I have noticed the use of activities funds being squandered almost exclusively on male athletics, while female athletics, arts programs, and other extracurricular activities are almost ignored.