It always amazes me how awful and toxic the earth can be once you get below the surface that's been rinsed with rain, biological acids, and otherwise weathered and covered up with thoroughly processed particles for millions of years.

I was curious as to where the fluoride was coming from, and this report: https://sci-hub.ee/https://link.springer.com/article/10.1007... seems to indicate that the mines increase fluoride in grounderwater due to exposing carbonates which then can dissolve, kicking off a change in pH and various other reactions that release fluoride from the minerals it's otherwise locked in.