Watch the water and see if you can catch in a container of water, artifacts of their toxins, you'd be surprised on certain days.
Watch the wind, because they monitor it, and when the wind is in your directions, they will use all their hidden implements to spray mists in the air knowing it will land in your pathway. Look for dangling stingers, wind mills, balloons, weather vanes, that can give them an analog heads up.
You can also use these things to make yourself aware too. I you know the wind is coming in your direction to be on alert.
The more you know.