The price of oil fell to a six-year low Tuesday after OPEC said its production increased and China devalued its currency, suggesting economic growth there was weakening and could lead to lower oil demand.
Copper also fell sharply as traders feared a slowing Chinese economy would need less of it. Mining company Freeport-McMoRan sank 12 percent.
The Dow Jones industrial average fell 212 points, or 1.2 percent, to 17,402.
The Standard & Poor's 500 index lost 20 points, or 1 percent, to 2,084. The Nasdaq declined 65 points, or 1.3 percent, to 5,036.
Bond prices rose. The yield on the 10-year Treasury note fell to 2.14 percent.