Fluoride (F-) is the mildly toxic ionic form of the element fluorine. It is a common additive to toothpaste, mouthwash, and water throughout the developed world. It is commonly thought to work to prevent tooth decay.
In 1978, Michigan became the first state to repeal mandatory fluoridation laws, leaving the decision to local jurisdictions. Many municipalities have since mounted successful challenges against mandatory fluoridation laws.
Fluoride Fears in Pop Culture
The character Jack D. Ripper from Dr. Strangelove starts a war over his concerns about excessive fluoridation, signified by his motto, "POE" or "Purity of Essence."