Now that large swathes of China are frequently shrouded in smog people may no longer believe that it is a sporadic extreme weather condition that befalls certain regions.

A National Development and Reform Commission report, published on Thursday, lends credence to the contention by saying that a quarter of the Chinese mainland has been shrouded in and some 600 million people have been affected by smog since the beginning of this year. Citing Beijing as an example, the report says that in January the capital experienced only five days which met the grade-II weather standard.

The pressure of economic downturn and increasing industrial energy and electricity consumption, however, pose a tough challenge to China's energy conservation and emission reduction efforts, the NDRC warned.