I can only guess it was mosquito spraying here in Clive. My family and I had just arrived home after a 750 mile drive from Ohio. We were just about done unpacking when a truck making a sound like a large generator came around the corner emitting a FOG CLOUD. As we tried to figure out what it was the smell was chemically finding its way into our nostrils.
It was a scene from a horror movie as we heard the truck head our way…COME OOOOONNNNNNNN…GET INSIIIIIIIDDDDDE!!! (Say it in the Arnold voice and it will make you laugh)
My wife bolted in and I shut the garage door just as the evil truck bolted past the house. Phewwwww. Just made it.
I haven’t seen that kind of spraying since I was a boy in CA. Back then it was done via helicopter for Mediterranean Fruit Flies.