Okay, no, the Three Gorges Dam does NOT explain the problem. This game I didn't have the Three Gorges at all, but still no unhealthiness from the coal plant. After the game was over, I went back and checked, and the Dam was on my continent, and I thought maybe it was given all the cities on the continent the benefit of it, even those not belonging to the owner. However, I then went and built a coal plant on an island off the coast, and, sure enough, still no unhealthiness. This seems like an awfully significant bug. Hasn't anyone else noticed it? If I post it here, will someone likely do something about it?
Scott Orr