http://edition.cnn.com/2016/05/31/africa/nigeria-cities-pollution/index.html
The issues of PM2.5 are considered to be symbol of newly industrialized countries such as China.
But, I didn't know the situation in Nigeria is more serious than those countries.
But, I'm sure that developing nations have a problem that the easiest way to deal with rapidly increasing population is to prepare infrastructure emitting exhaust gas.
So, the problem of PM2.5 or 10 will become more serious than newly industrialized countries.