Light aviation contributions to pollution are so small as to be insignificant, I did see figures that suggested that the annual U.K. GA fuel burn was equal to the fuel burn for an hour on the M25 at rush hour.
I don't know the sorce of these numbers but I think it sums up the scale quite well.
Did facts ever keep politicians away from stupid decisions?
I just read in a German newspaper they plan to ban Diesel powered cars from Stuttgart if they do not comply with Euro 6 regulations - their contribution to pollution in that town was estimated to be less 5% ... It is all about ideologies, not reality. I will be allowed to burn 100LL on top of their heads, but can not take the 2 year old car of my friend there to drive into town?