It is known that in WW1 "battle" gas was used for the first time. This information is used in a plethora of sci-fi stories and comics. For example it is used in Wonder Woman. What if the substances that were tested for their "effectiveness" as a battle gas would have suddenly started spreading from factories around the world? The epicenter of this catastrophe will probably be Germany and all around.
The main question is whether it is possible to spread those fumes all around the world by meteorological shifting of our planet?
I am looking on problem where I want to use this as a mechanics for human physiological changes.
Example: "Various substances were mixed in the stratosphere, where different gases will have different abilites and the mixture will be spread around the world and distributed with heavy rain back down on the surface."