The fluoride concentration in tap water is like 0.7mg/l. Toxic dose is 60 mg/kg, but 0.2 mg/kg is enough to cause some gastrointestinal discomfort. If I chug 16 liters of tap waters after I brushed my teeth I'll have some gastrointestinal discomfort from fluoride but I'll probably die from water poisoning first.
Cyanide is famously deadly, yet you eat it every time you eat an apple. Concentration matters.
Table salt would also kill you if you ate 1cup/2,5dl of it in one sitting.
The fluoride concentration in tap water is like 0.7mg/l. Toxic dose is 60 mg/kg, but 0.2 mg/kg is enough to cause some gastrointestinal discomfort. If I chug 16 liters of tap waters after I brushed my teeth I'll have some gastrointestinal discomfort from fluoride but I'll probably die from water poisoning first.