the problem with your machines causing pollution is it opens the door for a new form of greifing (pollution machine under victims micromanaged ic2 farm)
so here is an idea for a dedicated pollution biome. the main part of the idea is all stone is in a constant state of slow decay inside the biome smooth stone will eventually turn in to cobble and cobble will eventually turn in the gravel (stone bricks stop at the cracked stone bricks stage) gravel is also the biomes main soil block the only life that would could be found naturally occurring is vines, villages(the biome would be relatively flat like plains or desert)(the village also increases the zombie spawn rate), and hostile mobs. the biome would also generate structures in the form of industrial ruins made out of construction foam these ruins would have been picked clean for the most part you would be lucky to salvage a few luminators or some scraps of wire, a few blocks of reinforced stone from a blown out reactor housing, maybe a machine block or an iron furnace if alblaka smiles upon you. the biome would also have a unique danger when your in the biome with out a complete rubber suit(or quantum suit) you gain the polluted status effect(like regenerate or hunger) what this does is stone that you stand on will decay more rapidly and the effect lasts for some time after leaving the biome (or putting a suit on) causing you in a limited sense spread the pollution. also just for kicks pigs that wonder into the biome turn into zombie pigmen.
downsides: more hostiles, less food, looks plain ugly, ground could give way at any time especially if your not wearing a suit, could damage surrounding biomes if you are careless
upsides: salvage(but more effort to find than its worth), pre-built creeper proof home for you to fix up and live in, roleplaying, unlimited source of cracked stone bricks
EDIT:and how about cows and chickens drop rotten flesh in this biome as well