I'd start at compulsory water fluoridation. Here's a pretty decent synopsis (though now dated): https://web.archive.org/web/20140313192649/http://archive.le... . Bonus: Edward Bernays makes a special guest appearance in this tragedy.
For instance, we know that the gut microbiome has wide-ranging effects from digestive disorders to arthritis and auto-immune problems to obesity as well as mood and cognition. Here's a university study showing 54% of the bacteria in human gut microbiome are sensitive to glyphosate: https://www.sciencedaily.com/releases/2020/11/201120095858.h...
It may be the case that the skyrocketing rates of obesity or depression/anxiety or other chronic conditions have roots in chemicals like glyphosate disrupting gut microbiome or endocrine systems.
pesticide == (herbicide || insecticide)