WASHINGTON (AP) - The American workplace is grueling, stressful and surprisingly hostile.So concludes an in-depth study of 3,066 U.S. workers by the Rand Corp., Harvard Medical School and the University of California, Los Angeles. Among the findings: Nearly one in five workers - a share the study calls "disturbingly high" - say they face a hostile or threatening environment at work, which can include sexual harassment and bullying.