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Not the fluoride in the water thing again. Fluoride is used to preserve your teeth and is diluted in municipal supplies so as not to cause any health concerns. The national health and medical research council (of Australia) (2017) conclude that "the evidence shows that water fluoridation at current Australian levels reduces the occurrence and severity of tooth decay. Water fluoridation at current Australian levels is associated with dental fluorosis. In Australia, however, most dental fluorosis is very mild or mild, does not affect the function of teeth and is not of aesthetic concern to those who have it" (p. 4). I imagine that health conscious Californian municipalities would ostensibly assert similar findings.

https://www.nhmrc.gov.au/_files_nhmrc/file/17378_nhmrc_-_information_paper.pdf