Pesticides and herbicides applied by air drift, of course. That’s the point. If they just fall to the ground, they won’t kill off what they are designed to kill off.
If you are seeing plants on your property droop inexplicably, investigate immediately and try to determine if a neighboring property has been subjected to any recent application of herbicides. If you suspect drift, contact PennState Extension immediately for advice. They may be able to test the plants quickly and determine the cause. See more here.
Of course, keep an eye out for any potential toxics being applied anywhere near you and politely inform neighbors that if the wind is blowing your way, you will be documenting any damage to your plants.
If anyone in your family has a personal sensitivity to chemicals, they should apply to be on the state’s Registry of Pesticide Hypersensitive Individuals; see info here. This registry does not include herbicides and fungicides, but chances are, if your neighbor is into poisons of one sort, their or their “landscaping” company is applying others.
The registry does not prevent spraying, but it requires that you receive advance notice, so that you can act accordingly.
The manufacturer of one anti-mosquito spray commonly applied by truck says that it kills mosquitoes at 300 feet. Draw your own conclusions about the scope of potential damage from such sprays.