A crackdown on polluting industries in northern China for an unprecedented five months over winter is not a one-off and could hit Australian iron ore and coal exports.

The winter pollution shutdown, which began in September and will run until March, is set to continue, China's environment minister says.

Australian iron ore and coal exports have been hit by a slowdown in Chinese demand since the crackdown on pollution. Steel mills and cement makers in some provinces have had to cut production by 50 per cent, and the sale and use of coal is banned in other cities.

In previous years, the winter shutdown has only lasted a few weeks."This is not a one-off, it will continue in the future," said environment minister Li Ganjie of the new measures.