Your premise is wrong. This is called the Environmental Kuznets Curve (EKC):
https://journals.plos.org/plosone/article?id=10.1371/journal...
https://journals.plos.org/plosone/article?id=10.1371/journal...
The solution to pollution is more economic development, not less. This becomes even more true once demographic transition effects (like declining birth rates) start to kick in.