Steven Slott, I think the terminology you're looking for is natural Fluoride processes include the weathering and dissolution of fluoride rich minerals, emissions from volcanoes, geothermal activity, and marine aerosols. versus Anthropogenic fluoride sources include the release of processed waters and waste from various industrial sites, including steel, aluminum, copper
and nickel production, phosphate ore processing, phosphate fertilizer manufacturing and use, and glass, brick, and ceramic manufacturing.

Phosphate ore production and aluminum manufacture are the major industrial sources of environmental fluoride pollution. The use of fluoride containing pesticides and combustion of the coal and fuel also contribute to fluoride dispersion. These processes result in accumulation of fluoride compounds in the surface waters and groundwater reserves, air, soils, and in the living organisms.  

Thus, the main source of fluoride for humans is Fluoride tainted drinking water. 

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