Probably from Infowars or PrisonPlanet. For some stupid reason, there seems to be a significant number of people that believe in this "chemtrail" nonsense. They DO seed the clouds from time to time with silver iodide, but that has been happening for DECADES. The purpose is to make it rain more in a specific area. I'm not aware of the hazards to humans of silver iodide, if there are any. Of course, when one messes with mother nature, she seems to exact revenge in one form or another.