Coastside County Water District has very low levels of naturally occuring fluoride in our source waters: 0.24 parts/million [ppm] in Denniston Reservoir, 0.32 ppm in the Denniston well field and 0.18 ppm in the Pilarcitos well field. The maximum contaminant level [mcl] is 2 ppm. Since the San Francisco Public Utilities Commission (SFPUC) initiated fluoridation in 2005, fluoride levels in Upper Crystal Springs Reservoir have risen from 0.2 ppm to 0.85 ppm.

Below is helpful information from the California Department of Public Health about fluoride: