Is a pesticide that influenced society by increasing crop yield, but it also caused human and animal sickness.

Well there actually plenty of such things. In particular though I think your looking for something like DDT. or DDT is a organochlorine that was used widespread throughout the world as a pest killer, in particular insects. However it is extremely toxic and mutagenic and many problems were noted when the runoff when into the river supply and was uptake by fish, who were then eaten, in particular bald eagles. Eagles started dying and were incapable of laying viable eggs because of the agent leading to a near extinction of the species.