better question is "what is it not in", since it is in almost all main commercial products in the USA. Like take 'drinks' for example.....Maybe a can of ICED TEA. You buy it thinking it is TEA. But what do you make Tea with? Water. What if you use, fluoridated water to make tea...
That goes for ALL main drinks.
It also goes for your MUNICIPAL CITY WATER.
It also goes into many foods and fast foods and, well, its everywhere.
They use it to get people to Vote for evil, and to castrate themselves, and to think that, all races are equal, and that feminism is good, and that, well, you get the picture.

Impact of fluoride on neurological development in children
https://www.hsph.harvard.edu/news/features/fluoride-childrens-health-grandjean-choi/