[Lenneth]

One other potential possibility that is rarely if even mentioned at all is Pesticides & Herbicides.

I was born & grew up in a Small farming town, the town was regularly sprayed by crop dusters with god knows what, even nowdays little is really known about whatever herb/pesticide is the current "in thing" to use actually does to humans, and the only time something is really done/researched is when it causes some epidemic of some horrendous health problem.