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.

[–] KairuByte@lemmy.dbzer0.com 13 points 10 months ago* (last edited 10 months ago)

High concentrations of fluoride, sure. It’ll upset your stomach. Can even be toxic if you drink too much, but we’re talking over 10mg a day, when most of the time 1L of water has 0.7mg of fluoride. So unless you’re drinking over 14 liters of water a day, you’ll be just fine. And if you’re drinking that much water, you’re already at risk of water intoxication which is more concerning.

But in order to actually cause real harm you’re going to need to be eating large amounts of toothpaste and such.

Edit: To put this into perspective. Vitamin A, an essential vitamin humans require, which we literally go blind without (among other things) can be toxic when you take more than 3mg of it a day. That’s less than a third of fluoride. Just because something can become toxic in higher doses doesn’t mean it’s toxic when used properly.