Methylmercury's Toxic Toll
More than 60,000 children are born each year in the United States with neurodevelopmental impairments caused by exposure in the womb to methylmercury compounds, according to new estimates by an expert panel convened by the National Academy of Sciences. The panel released its 290-page review of methylmercury's toxicity earlier this month.
Many industrial processes, especially fossil-fule burning, spew inorganic mercury into the air. Once it rains down, the pollutant undergoes a chemical transformation- methylation-into a much more toxic form. Fish and other aquatic life readily pick up and store the resulting methylmercury (MeHg) in their fat. (Science News 3-9-91.p.152)
Mercury is a trace contaminant of most coal. The poison has been getting out, too. Studies by the Enviromental 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 pollutition 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.