Unlike China, America's air is getting cleaner, and Pennsylvania is leading the way, where sulfur dioxide emissions were slashed by nearly 600 million tons from 2007 to 2011 or by about two-thirds. Georgia was second with a 400 million ton reduction. http://www.eia.gov/electricity/monthly/update/.
The Clean Air Act targets sulfur dioxide for reduction, because it is a precursor to particulate matter that causes sickness and early death and because it causes acid rain. The huge declines are nothing but good news.
The sharp declines in sulfur dioxide emissions are caused by large investments in scrubbers for coal-fired power plants, the shift to natural gas power plants, as they emit very little sulfur dioxide, and more renewable energy and energy efficiency.