"Over the past decade, environmental groups have pressured U.S. chlorine plants to stop spewing mercury, the toxic heavy metal that settles in water and makes its way into the food chain by contaminating fish and shellfish. In the past four years, five such plants converted to mercury-free technology, cutting the industry's mercury emissions by 88 percent, according to the Environmental Protection Agency.
But this success has created a new environmental problem. Hundreds of tons of mercury acquired for use by the plants may be on the global market, where it could ultimately be used in small-scale unregulated 'artisanal' gold mining. Such activity might create environmental and health hazards in developing countries."