Foreign platinum and diamond miners have been restricted to only 49 percent ownership of their Zimbabwe operations by the black economic empowerment law.
The level 1 alert, the highest in China's four-tier pollution warning system, has been in place since March 1 and requires steel mills to curb output by 40%-70%.
Zimbabwe holds the world’s second-largest known reserves of platinum-group metals after South Africa, plus substantial deposits of gold, diamonds, lithium, iron ore, coal, chrome and nickel.