Who are you referring to? You use the past tense, which means you're probably not pointing a finger at china - which is hardly communist, making huge strides in cleaning up their emissions, and their emissions are largely the result of making stuff for the rest of the world. Which means you're probably talking about now-defunct communist countries, i.e. the soviet union?

So your argument against capitalism driving pollution in the hundreds of countries around the world where it appears to be driving pollution is a single example? A country that did most of it's polluting during a rapid industrialization with the stated goal of "catching up with the west". Meanwhile during that same soviet period not one but *two* rivers caught on fire in a single year in the USA.

Which is all to say that I'm unconvinced. It really seems like the driver of most of the pollution in the world has been capitalism. Perhaps communism is worse, but that doesn't let capitalism off the hook - it's not a two-choice binary system here.