Beijing is like an athlete trying to get into shape by walking on a treadmill yet eating double cheeseburgers at the same time. Polluting factories have been moved or closed. But auto emissions are rising as the city adds up to 1,200 new cars and trucks every day. Dirty, coal-burning furnaces have been replaced, lowering the city’s sulfur dioxide emissions. But fine-particle pollution has been exacerbated by a staggering citywide construction binge that shows no signs of letting up.