Methinks there is a lot of exaggeration concerning the toxicity of wasp spray for humans. Do you want it in your eye? No. Will you kill yourself if you get sprayed full on in the face? No.
First off there are dose to mass/ concentration issues. Insects, have tiny mass. Humans, big mass.
Second, there is the issue of how much gets absorbed through the skin. Probably not much except in extreme situations and long term exposures.
Third, there are medicines to counteract the anti-cholinergic properties (or is it the cholinergic properties-- I don't recall) and these are used in ERs all the time.
It is not uncommon for farmers and ranchers to overdose while treating a field with one pesticide or another.
The wasps drop because they are getting a big dose of poison relative to their mass. Humans, are pretty massive compared to wasps.
I worked in a toxicology research lab where the effects of pesticides on cattle and sheep were studied. And on the other side of the building folks studied the effects of pesticides on insect and pest control.
While that was a very long time ago and I don't remember all that I wish I could remember, and don't know the present formulation, my instinct here is to call bs on the dire claims that wasp spray is lethal or even effective beyond its effect as an eye irritant.
There are plenty of times I have sprayed wasp or hornet nests and the dang stuff has either bounced back onto me from the ceiling or wall or been carried back with the wind. Solution, wash it off.
I'm not saying it is impossible to get sick from this stuff, just that it would take a huge amount.