ABSTRACT
Fluoride content in natural waters in the northeastern part of the United States ranges from 0.02 to 0.1 ppm, while in the West and Midwest river waters, it ranges from 0 to 6.5 ppm, with an average of 0.2 ppm. Groundwaters contain from 0.1 to 8.7 ppm, depending on the rocks from which the waters «ow. ˆe level of F in seawater is about 1.2 ppm.
