This video says something about it chemtrails, nano particles, smart dust, this stuffs is around since the 90's, despite the dude plays a lot in the video, the info seems to be okay.

My point of view, they are poisoning earth most populated places and food production areas like big commercial farms (i have no proof of it but these farms are usually located in a large area, one beside another) I am always reading news from Brazil and in many occasions I did read about people writing about planes every week on scheduled time flying above their farms and ranches, leaving behind long line in the sky, it was like 5 or 6 lines in parallel in the different times of the day well apart from each other, but in scheduled time every week, and they never knew what it was, people started saying it was chemtrail, and others saying it was smart dust, I am just the observer, I do not know what it really is, but I do know they want us sick, debilitated, dependent.. it is no mystery or theory of conspiracy anymore, it is a reality and anything coming from them, can't be good.

Answering the question of this thread, I do not doubt it, but I am afraid my knowledge on this issue is very poor to contribute with something more useful.