After an extensive 2-minute google search, I found this explanation of the pollution haven hypothesis:
Pollution haven hypothesis argues that the industries that are highly pollution intensive i.e. dirty industries, have been migrating from developed economies to the developing world. It is argued that the environmental concerns of the developed economies caused them to enact strict environmental regulations, which have increased the cost of production of the dirty industries at home. On the other hand, the developing countries with their low wages and lax environmental regulations have been attractive alternative producers in these sectors.
Makes sense. Now consider this:
Environmental officials in Ohio say they won't follow their counterparts in Kansas and deny a coal-fired power-plant permit based on carbon-dioxide pollution.
Does that make Ohio the state equivalent of a developing country?