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.

Meanwhile, light sleet eased Beijing's notorious pollution on Thursday-- but levels still remained in the "unhealthy" range.

Air quality in the Chinese capital has mostly stayed between "very unhealthy" and "hazardous" for about two weeks on an index that measures particulate matter in the air.

To help combat the smog, Beijing has temporarily shut about 100 heavily polluting factories and took 30 percent of government vehicles off roads.