I take that as an insult .. and yet I don't take it seriously :D .. we're on the internet after all.

So I conclude from you posting this, that you distrust these trails.

Just one sceptical thought: let's say there were harmful substances in there. How infinitely widely diffused will they reach the surface? How many tons would a malicious actor have to spray of even the most potent chemical substance to maybe get a physiologically relevant effect.

Without having done any estimates, I'd say it's almost impossible to produce a harmful effect in this way.

You'd basically have to do it like they spray pesticides over crops with small airplanes .. very close to the surface.

Yep, I might also be completely wrong.