Mercury is a trace contaminant of most coal. The poison has been getting out, too. Studies by the Environmental Protection Agency have found that coal-fired boilers are the biggest U.S. source of mercury pollution. They release some 40 tons of the metal into the air each year—or roughly one-third of U.S. mercury pollution from all sources. A new study finds that China's reliance on coal burning has made that nation a world leader in mercury emissions.
Researchers at the Chinese Academy of Sciences in Changchun calculate that in 1995, the most recent year for which data are available, China spewed nearly 215 tons of mercury into the air. Another 90 tons or so ended up in cinder and ash. Electric power production proved the biggest single mercury polluter, sending more than 70 tons skyward each year. Residential coal burning released only one-quarter as much. Manufacturing sectors together released another 100 tons.