The same is true of our environmental Kuznets Curve. Those developing countries are curbing pollution at earlier stages of economic growth than we ourselves did. Largely, I would argue, because they know how to do it now that the west has already done it — therefore it costs less in lost growth and so, as is true of near all things which are cheaper, they do more of it.
It’s entirely true that large parts of the developing world are foully polluted at present. Just as the similar stages of our own economic development were. The good news is that, firstly, this is evidence that they are getting richer; Secondly, that they’ll curb the pollution as we did as they get richer yet; and thirdly, they’ll do it faster and earlier than we did. The air in New Delhi, Dhaka, Jakarta, and Beijing is vile today, but it’s a sure thing that it won’t be in 20 years.