Fluoride is one of the most abundant chemicals on earth. It can be poisonous even at low levels, because it accumulates in the human body over a lifetime.
Experts say that no chemical is absolutely safe for everybody.
No, chlorination is the process of adding chlorine at the treatment plant to kill bacteria, making the water safe to drink. Fluoridation has nothing to do with the water treament but uses water as a vehicle to treat the people who drink the water. Fluoride occurs in the water as an impurity with other known contaminants such as arsenic and lead. Just as one cigarette will not make you sick but a lifetime of smoking them will, one glass of fluoridated water will not make you sick. It is the accumulated effects of fluoride in your body over a lifetime that is causing medical concern.