Not saying you're wrong, but I'd like to share my own take, which is that one of the clearest, bluest skies I've ever seen was over North Korea. Because they sucked at doing "industry" compared to the South Koreans. In the 90s in South Korea, the rivers ran black and every corner you turned had its own putrid chemical smell from whatever fly-by-night entrepraneur had found a way to make a buck there. But that's an anecdote and I haven't been back to see what it's like now.