Eg, X-rays - 60 years from invention, popularity, child use, "crazy" people claiming they're bad, to suspicion they might be, conservative study, realising they're screwed, all kinds of safety standards being applied, and acceptance.
Radiation, thalidomide, PCB's, DDT's, smoking, Asbestos, etc. Sometimes it can be faster or slower, but 2-3 human generations is also pragmatic as you can reasonably assess effects on offspring as well as sufficiently-aged pioneers.
I mean, why are people even considering artificial sweeteners? Isn't it only because it's taken us all several decades to realise refined sugar is fucked after initially thinking it was great if not at least "safe"?
I'm happy ingesting organic fruit, but I understand many out there prefer their bodies used as profit-making devices.