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.