Exchange traded products that follow copper prices and miner stocks fell sharply Monday on European debt jitters combined with fears the global economy is decelerating.

The iPath Dow Jones-UBS Copper Subindex Total Return ETN (NYSEArca: JJC) was down 3% in early trading. First Trust ISE Global Copper Index Fund (NYSEArca: CU) and Global X Copper Miners ETF (NYSEArca: COPX), which follow copper miners, also weakened.

Copper prices fell to a nine-month low while global stock ETFs also retreated on worries Greece will default on its debt.

“People are becoming more concerned about demand prospects, especially with a weakening economic point of view,” said Michael Banks at Hermes Commodities, in a Bloomberg report. “This economic weakening is pervasive across all markets.”

Copper is seen as a leading indicator for the global economy due to its wide usage in building and industrial applications.

The copper ETN was down 13.7% year to date as of Sept. 16, according to Morningstar.

iPath Dow Jones-UBS Copper Subindex Total Return ETN