Slums

The mega cities of the developing world are expected to experience increasing rates of growth in the coming decades. The growth in population will be a challenge, but so will be dealing with the increase in air pollution.

"Slum tourism" is on the rise in developing countries around the world. Some say the tours help the affluent understand the dire situations faced by the world's poor, but others say it's just a way to help Westerners feel good about themselves.