A 40-car pile-up in Tianjin, China. It's just one of many incidents caused by thick smog that's causing havoc across northern China, as pollution reaches alarming levels. The pile up injured six people and caused a severe traffic disruption for morning commuters. Adding to the mess, nearly 50 flights were delayed at Tianjin Airport. Tianjin's air quality monitoring stations reported that air pollution had reached "hazardous" levels through the early afternoon.