The S&P 500 was down 0.5% to 2,106.78 in midday trading.
The Dow Jones Industrial Average was down 0.5% to 18,198.30 and the Nasdaq was down 0.7% to 4,975.40.
The yield on a 10-year Treasury bond rose 0.8% to 2.10%.
The price of gold rose 0.6% to $1,220.
Newport Beach-based American Vanguard Corp. was down 1.2% to $11 and a market cap of $321 million. The chemical company reported quarterly results below expectations.
Irvine-based AtheroNova Inc. was down 56% to about 3 cents a share and a market cap of about $300,000. The development stage pharmaceutical company filed for bankruptcy protection.