The S&P 500 was down 0.2% to 3,393.80 in midday trading.
The Dow Jones Industrial Average slumped 0.2% to 27,880.18.
The Nasdaq rose 0.1% to 11,154.09.
The yield on a 10-year Treasury bond decreased 0.9% to 0.69%.
Oil slipped 0.5% to $37.85 a barrel.
The price of gold was up 0.5% to $1,964 an ounce.
Irvine-based Montrose Environmental Group Inc. (NYSE: MEG) rose 4.5% to $30.29 per share for a market cap of $756 million. Shares in the air quality and environmental services company have doubled since its July 23 IPO at $15 a share.
Artificial intelligence company Veritone Inc. (Nasdaq: VERI) dropped 5% to $7.40 a share with a $205 million market cap. Shares in the Costa Mesa-based firm are still up about five-fold since a 52-week low in March.