This could be a modern-age wonder(which affects all civs), or something voted on like the council stuff in SMAC.
Simply, it would lower production by a factor of 0.5 in all cities, but limit pollution to 4 units per city. The tech "clean automobiles" would lower the limit to 2 units, the tech "Recycling" would lower it to 1, and lower the penalty to 0.25, and the tech "Efficient Production Methods" could lower the penalty to 0.
Simply, it would lower production by a factor of 0.5 in all cities, but limit pollution to 4 units per city. The tech "clean automobiles" would lower the limit to 2 units, the tech "Recycling" would lower it to 1, and lower the penalty to 0.25, and the tech "Efficient Production Methods" could lower the penalty to 0.

