Fluoride is a naturally occurring substance found in rocks that leaches into groundwater; it's also found in surface water. The natural level of fluoride in the water varies depending on the type of water (groundwater or surface) and the type of rocks and minerals it's in contact with.

Where is most fluoride found?

In adults, about 50% of absorbed fluoride is retained, and bones and teeth store about 99% of fluoride in the body [1,3]. The other 50% is excreted in urine [1]. In young children, up to 80% of absorbed fluoride is retained because more is taken up by bones and teeth than in adults [1].

Where is sodium fluoride found?

In nature, it is found only in compound forms, such as the ore fluorspar (calcium fluoride) in soil and rock. To form sodium fluoride, hydrogen fluoride (derived from fluorspar) is neutralized by sodium hydroxide from brine, and dried into a powder.