Toxic smog
Beijing chokes in heavy dust as sandstorm blows in
The alert would remain in place until 1200 GMT on Wednesday, the agency said.
Key areas facing such restrictions are the Beijing-Tianjin-Hebei zone in the country’s north and the Yangtze and Pearl River deltas further south.
Under an orange alert, factories that make furniture, cement and other heavy industry must limit output by between 30 and 50%.
A US embassy measure of tiny particulate matter PM 2.5 showed a reading of 608 at 10 am when the safe limit is 50.