Workplace accidents are sudden or unexpected events that lead to physical and or mental injury or death. In the U.S., there are an estimated 337 million workplace accidents each year. A workplace injury can take place at the physical location of the workplace or elsewhere. Because they’re typically referred to as “sudden,” workplace accidents differ from occupational diseases that are caused by repeated exposure to a harmful substance or activity. For instance, if a piece of equipment injures your back, that’s a workplace accident. If a repetitive work activity eventually causes back problems, that is an occupational disease.