Health care and materials companies fell the most in early trading Monday.
The Dow Jones industrial average lost 117 points, or 0.7 percent, to 16,198 as of 9:35 a.m. Eastern time.
The Standard & Poor's 500 index slipped 14 points, or 0.7 percent, to 1,917. The Nasdaq composite slumped 29 points, or 0.6 percent, to 4,657.
Alcoa bucked the trend, gaining 3 percent after saying it would split in two.
In Europe, Glencore plunged 24 percent after an investment bank warned that the company faced a bleak future if commodity prices don't recover. Volkswagen also fell 8 percent.
Bond prices rose. The yield on the 10-year Treasury note fell to 2.14 percent.