The U.S. EPA on Wednesday announced it’s giving up its effort to push through two unpopular changes to air-pollution rules before President-elect Barack Obama takes office. The changes, in the works for years, would have eased restrictions on power plants’ emissions near national parks and allowed some of the country’s dirtiest power plants to emit more air pollution. Clean-air advocates breathed a tentative sigh of relief, but reserved full exhalations for Jan. 20.