It's not just China or India. It's the entirety of Southeast Asia and West Africa for much of the year too (typically starting in the next month or so). I've lived in Southeast Asia for a couple of years of my life and even had to move my family out of Thailand because the pollution is so bad (not just air pollution).

AirVisual [1] shows the impact of these areas pretty dramatically. At times, the air pollution in Africa is so bad that its impact can be felt directly in Brasil.

[1] https://www.airvisual.com/earth?nav