China burns more coal than any other country, about 1.4 billion tons in 2002. The amount is forecast to be 3.3 billion tons by 2020. China is also the world's largest producer of mercury emissions, with coal combustion as the greatest single source. China produces about three times more mercury per ton of coal burnt than the U.S. because of a lack of modern pollution control technology and because the average concentration of mercury in Chinese coal is about 150 ppb as compared with about 100 ppb in the U.S.