China will track second-hand vehicle emissions to help improve air quality, said a statement from the Ministry of Environmental Protection (MEP) on Tuesday.

The statement said environment protection authorities should establish an archive for emissions data of second-hand vehicles to prevent the transfer of pollution sources.

It also called for an information network for emissions data and stricter supervision over vehicle emissions inspection stations.

Heavy air pollution in China has persisted as the national observatory renewed an orange alert for smog on Tuesday in northern, eastern and central regions, with smog blanketing the regions since last Friday.

China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.

The smog is predicted to dissipate starting the evening of this Sunday with the arrival of a cold front, the MEP has said.