This is a very polarizing debate: One side says that flouride is good for the teeth and preventing cavities while the other side says that fluoride is a deadly poison and causes long-lasting health issues.
Many cities add flouride to the water which is why it is many water supplies.
An active ingredient in many pesticides and rodenticides is fluoride. which is accutely more poisonous than lead. Overdose leads to serious toxic symptoms. Some experts feel that chronic doses of fluoride can lead to cancer, diabetes, throid and neurologoical disorders, heart disease, arthritis and osteoporosis.
Any level is frequently undesirable.
Here is what one expert says: "Fluoride and fluoridation will go down as one of the greatest controversies of the 20th century. Up until the early 1940's, fluorine's effect on life was always deemed poisonous. It was proven to be altering enzymes used by living organisms to carry out a multitude of essential processes. Fluorine, the most reactive element on the planet, is also the strongest free radical. Scientists in the 1930's and 1940's experimented with this element to create the most deadly nerve gasses, rocket fuel, and radioactive U235 for the bomb. As a wood preservative, rodentcide and insecticide, fluorine compounds are second to none. As an Orthodontist, I began investigating the increasingly prevalent lines and spots that I saw on the enamel of children. Like rings on a tree, they indicate excessive fluorine exposure. I started to ask the question, 'How does fluorine cause these marks?' Chronic doses of fluoride, like arsenic and lead, accumulate in our bodies causing a blockage in the way cells breathe and leads to the malformation of collagen. Cancer, diabetes, thyroid and neurological disorders, hormonal imbalances, heart disease, arthritis and osteoporosis have all been linked to chronic fluoride ingestion. We are now exposed to increasing doses of fluoride from toothpaste, rinses, water, food, medicines, showering, bathing, and even the air that we breathe. Our environment has become a literal fluoride dumping ground."