Iron ore prices dropped to their lowest since September amid a lack of demand in China, with some mills in the world’s largest buyer ordered to suspend production before a summit of world leaders in Beijing.

Ore with 62 percent content delivered to Qingdao fell 1.2 percent to $78.63 a dry metric ton yesterday, the lowest since Sept. 30, according to Metal Bulletin Ltd. Prices dropped in the final two weeks of October, and a retreat to less than $77.97, reached on Sept. 29, would be the lowest since September 2009.

The raw material used for steel fell into a bear market this year as Rio Tinto Group (RIO) and Vale SA expanded supply, spurring a global glut just as economic growth in China slowed. Asia’s biggest economy will host the Asia Pacific Economic Cooperation forum in the capital from Nov. 7-12, prompting authorities to order factory shutdowns to ensure clean air.

“Demand remains weak as Chinese buyers sit on the sidelines, with many Beijing steel mills forced to halt production leading up to the APEC meeting,” Australia & New Zealand Banking Group Ltd. said in a daily report today. Prices dropped yesterday amid a lack of bids, the bank said.

The measures in China are aimed at preventing smog from enveloping the city during the event, which is scheduled to be attended by U.S. President Barack Obama, Japanese Prime Minister Shinzo Abe and Russian President Vladimir Putin. The provinces of Hebei and Shandong will bear the brunt of output losses.

The global iron ore market needs to absorb a surplus of about 110 million tons next year, almost double the estimated 60 million ton glut in 2014, Goldman Sachs Group Inc. said in an Oct. 23 report. The collapse in prices may have further to run as global supply increases and steel-demand growth slows, according to Moody’s Investors Service.