At this time next year, the world's finest athletes will converge in Beijing for the 2008 Olympics. They will sprint, leap, and toss their way to gold-that is, if they can get a breath of clean air. China has some of the worst pollution in the world, and bad air kills 400,000 Chinese annually [see "China's Green Evolution." In anticipation of the Olympics, Beijing has launched a massive cleanup. Some 200 factories in the area will be relocated.