I disagree with the entire Civ pollution system. Never, in all of human history, has an area the size of Rhode Island become completely unusable. For that matter, no area that large is completely contaminated (not even around Chernobyl nuke plant, which is still in use BTW).
Pollution needs to cause unhappiness and (especially in the early Industrial times) lower life expectancy. Thus, when you are producing more shields or have too many people, the ability of your people to grow in population would become less, however, it would be coupled with the fact that your technology would likely facilitate longer life (hospitals, anti-biotics and other meds, ...)
Thus, Industrialization (and the building of factories) should reduce the ability to grow the population. Hospitals (representing all better medicine) would facilitate the ability of the population to grow. Exactly how this should be done is beyond me, but the idea of 4 or 5 superfund clean-ups each turn just does not make any sense at all.