I gotcha. I'm also thinking of mass transit, parking, retail, and probably a few more things I've forgotten about. Even the local geography/weather can play a part in terms of pollution. If we go from a subdivision with 40 houses to apartments with 4,000 units and update the existing infrastructure, 4,000+ cars starting up every day could result in a significant increase in exhaust pollution that we may not be able to design around. The climate/geography are going to be the climate/geography.