Which country have the most air pollution on Earth ?

In 1992, the United Nations described Mexico City's air as the most pollution on the planet. Six years later, that air earned Mexico the reputation of the wors dangerous city in the world for children. A reputation Mexico has been working hard to improve. But despite more than a decade of stringent pollution control measures, a haze hangs over the city most days, obscuring the surrounding snow-capped mountains and endangering the health of its inhabitants.

Many factors have contributed to this situation: industrial growth, a population boom (from three million in 1950 to some 20 million today), and the proliferation of vehicles. More than 3.5 million vehicles — 30% of them more than 20 years old — now ply the city streets.