A recent joint report (PDF) from the Nature Conservancy and the Cary Institute also stressed the importance of setting and implementing critical loads for SO2 and NOx, as well as establishing more comprehensive, integrated air pollution monitoring systems.
Still, efforts to reduce emissions of acid rain precursors in the United States don't do much to solve the problem in countries on the other side of the globe. In 2005, China was the biggest emitter of sulfur dioxide in the world, sending up about 25.5 million tons. Beijing did recently announce that, by next year, the country would reduce SO2 emissions by 10 percent from those 2005 levels. Two-and-a-half million tons is more than an acid raindrop in the bucket, so at least that's a step in the right direction.*
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*Correction, Aug. 18, 2009: The original sentence read "two-and-a-half tons."