A new study shows a 25 percent drop in the rate at which mercury is accumulating in Minnesota lakes. The decline comes despite the fact that mercury contamination levels worldwide continue to climb. Like acid rain, mercury pollution is hard to fight, since it can spread thousands of miles from its source. The study, published in the April issue of Environmental Science and Technology, offers some of the first evidence that local cutbacks in mercury emissions are paying off close to home. Minnesota Public Radio's Mary Losure reports.