Stocks head lower for a third day straight

The U.S. stock market was heading for a third loss in a row Wednesday as investors worry about slower economic growth in China and lingering tensions in Ukraine.

The Standard & Poor's 500 index fell six points, or 0.3 percent, to 1,861 as of 10:25 a.m. ET. The Dow Jones industrial average shed 50 points, or 0.3 percent, to 16,300. The Nasdaq composite dipped 13 points, or 0.3 percent, to 4,293.

The catalyst for the latest market downturn was news this week that Chinese exports slumped in February. Since China is a big consumer of raw materials and energy, commodities such as copper and iron ore have dropped sharply. Copper has fallen to its lowest level since 2010.

Nine of the 10 industry sectors in the S&P 500 index fell. The only one that rose was utilities. Among the S&P 500 index's big decliners were insurer Progressive, which shed 69 cents, or 2.9 percent, to $23.82, and homebuilder PulteGroup, which slid 52 cents, or 2.6 percent, to $19.41 following a report that applications for home loans declined from a week ago.

Mining companies topped the list of gainers in the S&P 500 index in early trading. Cliffs Natural Resources led the pack, rising 55 cents, or 3.1 percent, to $18.53. Newmont Mining added 39 cents, or 1.6 percent, to $24.74.

Geron plunged $2.94, or 66.6 percent, to $1.47 in early trading. Concerns about potential liver damage prompted U.S. federal regulators to order research suspended on its blood disorder drug.

Germany's DAX fell 1.5 percent, the CAC-40 in France fell 1.4 percent and Britain's FT-SE lost 1 percent.

Earlier, Hong Kong's Hang Seng closed down 1.7 percent. China's Shanghai composite dropped 0.2 percent. South Korea's Kospi shed 1.6 percent. In Japan, the Nikkei 225 slid 2.6 percent. The Bank of Japan decided not to expand its already lavish monetary stimulus following a 2-day policy meeting.