"A transcontinental conveyor belt of bad air" is exporting mercury and other pollutants from China's 2,000-plus coal-fired power plants and posing risks of mercury buildup for the world's water and food supplies. Improved monitoring by satellites, airplanes, and supercomputers are allowing scientists to track the pollutants "with unprecedented precision," reported Matt Pottinger and Steve Stecklow from Beijing and John Fialka from Washington, D.C. One factor: China air quality rules allow the facilities to pay an annual fee rather than necessarily install costly control equipment. They report that "some scientists" say 30 percent or more of mercury settling into U.S. soil and waterways comes from other countries, in particular from China, rendering local solutions inadequate ... and even providing some locals an argument for doing nothing. Another key factor the reporters detail: mercury emissions across the U.S. and Europe are falling, but rising in China, already believed to be the world's "largest source of nonnatural emissions of mercury."