A recent question was about the Asian Brown Cloud, which I couldn't help with at the time. But I'm now doing some reading, and see that there's a recently released major report "Atmospheric brown clouds: Regional assessment report with focus on Asia. So there's a solid place to go for information.
I'm also a bit amused by who the lead author is. Not that he's amusing, V. Ramanathan is a serious, careful scientist. But that the author I wind up referring you to was one of my doctoral committee members. Science is a small world.