What is the pH range of air pollution?

Question

What is the pH range of air pollution?

Answer 1

There is no real answer to this question, because pH is the negative log of the H+ ion concentration in an aqueous solution.  "Air pollution" refers to atmospheric gases, so there cannot be any hydrogen ions floating around.  

On the other hand, there can be gases like the nitrogen oxides and sulfur dioxide in air pollution.  When those gases are absorbed by water (such as rain drops), they form nitric and sulfuric acids.  That water would then have a very low pH, depending on the concentration of the acids.