National Public Radio: FLORA LICHTMAN, HOST: Last weekend, air pollution levels in Beijing hit a record high, cloaking China's capital in a thick smog and forcing residents inside. The air quality index measures ozone, carbon monoxide and particles, basically the stuff in the air, and the scale - the index scale that we use for particulate matter here in the U.S. goes from zero to 500. If this reading goes up past 300, that's considered a health hazard. Well, last Saturday, monitors in Beijing recorded an air quality...