Running 1.21, and every time I play, I cannot get rid of pollution. More specifically, population pollution. I've tried many ways to avoid it or eliminate it, but it never works. Once in the industrial age, and cities hit 13 or even 12, they start polluting, and continue, even after I build ecological improvements. After recycling plants, mass transit, solar/hydro plants, I am always left with one pollution icon in the city view--always. It's just enough to plunge a city into starvation now and then.
I am out of ideas on how to fix this. I even tried applying negative pollution values to the ecological improvements in the editor, but that didn't work either. Anyone know what I am doing wrong?