Construction workers are at risk of death or serious injury if they enter an unprotected trench and the walls col¬lapse. A trench is defined as a narrow underground excavation that is deeper than it is wide, and is no wider than 15 feet or 4.5 meters [OSHA]. Hazards associated with trench work and excavation are well defined and preventable.

With nearly 126 million full-time U.S. workers at risk of occupational illness and injury, it is critical to prioritize our research efforts to address the most important issues. One approach used by NIOSH and its partners to establish priorities is to consider the burden, need, and impact of potential research topics.