I really liked the video by Iron Seagull (I think) in which he talks about what neighbourhoods he is planning to make industrial and polluted, and which ones he will change to Green. I agree with him that at least one district of San Myshuno, perhaps the Spice District, is just crying out for some pollution. All my Sims have fireplaces, sometimes several per household, so I may end up with more polluted neighborhoods than I want, unless I go through and also add a lot of eco-friendly appliances to help mitigate this.