In the USA we are blessed in that we have systems so effective like the MistAway mosquito misting system that use a highly diluted ultra low volume insecticide that only requires a "Caution" warning label and that is BEFORE we dilute it in our machines another 100 or more parts water to only 1 part insecticide. Like other low impact bug sprays bought at any hardware store the "Caution" rating is the lowest rating issued by our government on consumer chemicals. As always, follow directions, and use common sense.
One can only imagine what chemicals are used in third-world to combat mosquitoes.
Look at these guys in full body protective chem suits. What the heck are they spraying and at what concentrations?