Concemtration etc
Guys,
The Statistically Safe concentration needs to be determined with specifics to Particle size and composition.
The particle size would be easy: similar to suspended dust and smoke found often over Africa/ Asia.
The composition would be trickier esp regarding quality of toxins and effect on breathing.
However, considering that even with deposits on cars etc, there are no widespread issues of running eyes, short breath etc,
It may be prudent to assume that the flight is possible in the plume.
Also it is one thing to fly into the cloud when released because concentrations are high, the time bound dissipation will always reduce the threat.