Buildings are shrouded in a dense smog near the CBD [ Central Business District] area in Beijing, capital of China, Jan. 12, 2013. Beijing was shrouded in dense smog for a second straight day Saturday. The smoggy weather will not clear up until Monday, the city's environment monitoring center said. Beijing's air is heavily polluted. Readings for PM2.5, or airborne particles with a diameter of 2.5 microns or less -- small enough to deeply penetrate the lungs -- were as high as 456 on Saturday. [ Xinhua/Luo Xiaoguang]