Slowing global economic growth and the passage of a new rule designed to curb speculation in commodities futures were pressuring exchange traded products that follow the price movements of copper and silver, two key industrial metals, on Wednesday.

Silver and copper funds led the decline in metals Wednesday. The iShares Silver Trust (NYSEArca: SLV) was down 3.5% at last check and iPath Dow Jones- UBS Copper Sub-Index Total Return ETN (NYSEArca: JJC) shed 4.7%.

Moody’s recently cut Spain’s credit rating, stoking concern of diminished demand for metals in Europe, and China has revealed that its economy was moving at its slowest pace since 2009 in the third quarter, report Yi Tian and Maria Kolesnikova for Bloomberg.

“Copper is under pressure because of a theme of slowing economies throughout the world,” Frank Lesh, a trader at FuturePath Trading in Chicago, said. “Prices will need to go lower to attract Chinese buyers as there’s ample supply” in China.

“Full-scale restocking might not kick in until the first quarter of 2012” Andrey Kryuchenkov, a London-based analyst at VTB Capital, said. “Also, we shall need some clarity on the Eurozone bailout, so that we avoid growth stagnation and another panic equity selloff.”

Copper is widely used in industrial industries and prices are correlated with the health of the global economy. Silver has many industrial applications and may also be found in electronic devices. [Silver ETFs Hit Hardest in Precious Metals Pullback]

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