TL;DR
Inform players what could happen if they change the pollution settings before creating the map.What ?
I suggest to add an infomational or warning tooltip to the pollution menu in the map creation menu. The player shall be informed about the fact, that when pollution spreads new but unrevealed map chunks could be created. Biters and biter nests will spawn and will possibly slow down the game. Also the savegame size could significantly increase.Why ?
The game performance on large maps could be way higher with the correct pollution settings. Also savegames could be way less huge.Reference: My own misconfigured savegame