ok you mother
air pollution diffusion works like this:
first, all pollution from industry is added to the pollution totals before diffusion.
now the rules of diffusion are as so:
pollution will only move to zones that have less pollution than the current zone.
up to 50% of the pollution on the current zone may move away each turn.
at 9 and less pollution on a zone, no pollution will move.
between 10 and 19, 1 points of pollution will move to each neighboring zone per turn.
between 20 and 29, 2 points of pollution will move to each neighboring zone per turn.
between 30 and 39, 3 points
and this is extrapolated all the way to infinity.
last, all pollution above sea zones, high level cities, and high level research is subtracted from the air.