I'm fairly certain socialist states polluted just as bad as capitalist states. As far as I'm aware they also did so in a more wasteful way, i.e. they produced less goods and services for the same pollution.
They polluted even worse. The Soviet Union was directly responsible for some of the greatest ecological catastrophes in history, including the drying of the Aral Sea.
I'm fairly certain socialist states polluted just as bad as capitalist states. As far as I'm aware they also did so in a more wasteful way, i.e. they produced less goods and services for the same pollution.