The majority of the nation’s dirtiest power plants are getting even dirtier, according to a report released yesterday by the U.S. Public Interest Research Group. The report was based on U.S. EPA data on smog, soot, and global warming emissions from power plants from 1995 to 2000. It found that greenhouse gas emissions increased 8 percent, with a total of 175 million tons of carbon dioxide released in the six-year period. Smog and soot emissions also increased at the majority of the plants, although the overall levels of those pollutants dropped, thanks to reductions at some other plants. The report comes as the Bush administration weighs changes to the Clean Air Act that could dramatically relax pollution standards for power plants.