China's booming economy is threatening to sabotage global efforts on climate change. But action has begun to rein in the Asian dragon's dire levels of pollution. Each day NASA's Aqua and Terra satellites pass over north-east Asia and take a snapshot of the world's scariest environmental problem. The photos often show a blanket of soot, sulphur, nitric oxide, ozone and dust that blocks out an area stretching from Beijing in the north to Xian in the west and past the Yangtze River. These toxins irritate the eyes, scratch the throat and lodge deep inside the lungs to cause the premature death of one Chinese person every 45 seconds, or 750,000 people a year.