Copper futures declined to the lowest since May on demand concerns after a manufacturing gauge fell from an initial reading in China, the biggest user of the metal.

A Purchasing Managers’ Index slipped to 50.2 in September from a preliminary figure of 50.5, and was unchanged from August, a report from HSBC Holdings Plc and Markit Economics showed. Numbers above 50 signal expansion. In Japan, factory output fell 1.5 percent in August, compared with a 0.2 percent gain forecast in a Bloomberg survey of economists. Copper dropped 6.1 percent this quarter.

“The data out of China and Japan was less than encouraging,” Michael Turek, a senior director at Newedge USA LLC in New York, said in an e-mail.

Copper futures for December delivery fell 1.6 percent to settle at $3.0075 a pound at 1:13 p.m. on the Comex in New York after touching $3.006, the lowest since May 1. The metal slipped 4.8 percent this month, the most since March.

On the London Metal Exchange, copper for delivery in three months lost 1.1 percent to $6,667 a metric ton (3.02 a pound).

Aluminum, tin and zinc also declined in London, while lead gained. Nickel, which yesterday entered a bear market, fell 2.2 percent, capping the biggest monthly loss since September 2011.

The Bloomberg Commodity Index headed for its biggest quarterly drop since 2008 amid signs of ample supplies in raw materials ranging from crude oil to wheat.