"Fluorosilicates do not require a toxicological assessment specifically for the fluorosilicate ion, because measurable levels of this ion do not exist in potable water at the fluoride concentrations and pH levels typical of public drinking water."
https://www.nsf.org/newsroom_pdf/NSF_Fact_Sheet_on_Fluoridation.pdf

It is easy to cherry-pick studies that confirm a passionate bias, particularly with a complex, emotional scientific topic that has thousands of published studies from decades of research.  That is just one reason to understand and seriously consider the scientific consensus – the conclusion of most experts in a subject.  In the case of fluoridation, overwhelming majority of evidence and the consensus of experts is that it is a safe and effective public health measure.

That is why over 100 national and international scientific and health organizations and their representatives recognize the public health benefit of fluoridation for preventing dental decay.