It's more of a sandblasting than poison, at least that's what I suppose...
Man, if the sandstorms are like the ones in Nevada Skies mod we are trully f**** depending when and where they happen.
-7 PE, -3 END, -2 AGL and +70 sneak are the effects and you can't see beyond 2 feet.
If they are radioactive you also gain +4 rad/s.
But they are great for making ambushes, providing you know the location you want to go, of course.