At least one study did make an effort to take things like income and other exposures into account. https://www.cnn.com/2019/08/19/health/fluoride-neurotoxin-can

At least one study did make an effort to take things like income and other exposures into account. https://www.cnn.com/2019/08/19/health/fluoride-neurotoxin-canada-study/index.html https://www.cnn.com/2019/08/19/health/fluoride-neurotoxin-ca... At this point I think fluoride falls firmly into the category of "needs more research", but if you're pregnant it seems like actively trying to reduce your intake of fluoride is a sensible precaution since that's unlikely to have any negative effect on you or the kid, but if fluoride does cause problems you could dodge a bullet before the science catches up.