Fluoride is poison. Fluoride, which occurs naturally in drinking water, is indeed a neurotoxin. As with all poisons, however, it's the dose that matters. Opponents point to warnings on toothpaste tubes urging people to call a poison control center if toothpaste is swallowed. Toothpaste, however, contains more than 1,000 times as much fluoride as fluoridated water. But a full tube wouldn't be a lethal dose for even a 2-year-old, 22-pound child, according to the Columbia University College of Dental Medicine.