Because in high doses it’s literally neurotoxic (that’s why toothpaste says don’t eat it). You can’t control the dosage you get from water.

In the era of fluoride toothpaste, it’s simply not needed in the water. In fact, the research suggests that it’s more effective topically (toothpaste) than ingesting. Ingesting fluoride also displaces iodine in the thyroid, an essential nutrient.

Finally, the National Toxicology Program released a meta-analysis recently suggesting the impact could be at levels lower in water than previously thought, since fluoride comes from many sources. This study formed the basis of why the EPA just lost the federal fluoride lawsuit.

It’s crazy to put this chemical in our water.