The size of the particles would be 1 micron in size or so. The EPA says that any particulate smaller than 10 micron size is toxic for humans, as it is easily absorbed into the lungs and soft tissue. If the EPA says something is actually toxic for us, that is one thing you can trust them on.

Also, you are correct in that the spray would disperse unreasonably, yet there is one factor that you need to take into account. The ChemCoctail mix is sprayed by aerosol, yet suspended in a polymer matrix that keeps it together and suspended and cloud looking.
The small size of the particulate makes it highly toxic for us toi breath. There is no doubt that we are breathing it, we are. As far as an earlier post as far as the height being too high, they spray much lower than you would expect. They spray at various altitudes. The polymer keeps it suspended and cohehisive, and we are breathing that as well. There are photos of this stuff and it is weird. Also, there is mold and viruses from the upper atmosphere that may attach to the polymer/fiber/chem haze and drop down to us. A massive increase in black mold and health problems could be related to any of these or other toxic elements that may be purposely or inadvertantly be tagging along for the ride.