pWall Street plunged on Monday, sending the Dow tumbling 150 points, as fears over the possibility of a U.S. government shutdown by the end of the day weighed on investors.ppAs of 10:20 a.m. Eastern, the Dow Jones industrial average dropped 125.94 points or 0.83 percent, to 15,132.30. The S&P 500 lost 11.54 points or 0.68 percent, to 1,680.30. The Nasdaq Composite dropped 24.46 points or 0.64 percent, to 3,757.53.