I've been playing the Romans on Emperor level and expanded very aggressively over a customized earth with big continental plates. Now I dominate 4/5 of the landmass, I signed peace treaties with all other civilizations (4 remaining) and I'm concentrating on building the biggest empire I've ever built, while winning through reaching Alpha Centaury. I've got 44 cities with a total population of over 224,000,000, and my pollution production is zero. And suddenly, I start getting polluted tiles all around each of my cities (which by now are about 31 in size, on average)! Is it a bug, or is there a reason for this sudden change? Now I'm forced to use Terraform every 3 turns to get rid of all the garbage at once, since most of my cities are fully grown and cannot support a Settler... and even with the "rework" trick, so much pollution is unmanageable anyway. So my best play till now has been completely spoilt by all this. Someone with the same problem (and hopefully, a solution as well)?