Anything is poisonous at a high enough dose. For example: Water poisoning. You can die from drinking too much water; it causes electrolyte imbalances. Or salt poisoning. Or the fat-soluble vitamins. And things that are traditionally considered “poisons” have a dose below which they are harmless. read more
Most people drink 2 or fewer liters of water a day, way below the amount where fluoride in tap water could possibly be a health issue. If you were drinking ten liters of water a day, the water itself would poison you. read more