It is the city of Linfen, China and spending about a day there breathing in the air is about the same as smoking three packs of cigarettes. The scary part is that there's a lot of cities in China like this. Sixteen out of the world's 20 most polluted cities are in China.

Linfen produces what any nation of over a billion people need - a ton of energy. It's an endless landscape of factories all spewing a bunch of toxic chemicals into the air and poisoning the land and the water. There's no clouds, just a permanent toxic smog hovering over the city. Linfen is located in the heart of Shanxi Province. Every day, thousands of coal trucks go between Linfen and the rest of China's cities. Then they come back empty for more. A lot of the environmental problems in China are very closely linked to the energy consumption.

The Dirtiest Place on the Planet