Learning ObjectivesRecall the past effectiveness—or lack thereof—of OSHA in lowering injury rates in the workplace, and the influence of the MSHA (Mine Safety and Health Administration) in the coal mining industry.Describe the course of fatal injury rates before and after revision of an ambiguous consensus standard governing trench and excavation jobs, along with introduction of a targeted inspection program in 1990.Explain whether and how changes in fatality rates depend on the size of construction firms and whether or not workers are unionized.In 1989 the US Occupational Safety & Health Administration revised the excavation and trenching standard. We examined fatal injuries from trench cave-in in the construction industry for five year periods before and after the revision in the 47 US states for which data were available for both periods. There was a 2-fold decline in the rate of fatal injury after revision of the standard, which substantially exceeded the decline in other causes of fatal injury in the construction industry during the same period. The decline was somewhat greater in large business firms but was evident in construction firms of all size classes. The fatality rate from trench cave-in in union construction workers was approximately half that of nonunion workers, but we were unable to determine whether this was best explained by union status, employment of union workers at larger construction firms, or both. This study provides evidence for the effectiveness of OSHA regulation in preventing fatal work injury.