Occupational safety and health, also commonly referred to as health and safety, occupational health and safety, occupational health, or occupational safety, is a multidisciplinary field concerned with the safety, health, and welfare of people at work.Workers around the world—despite vast differences in their physical, social, economic, and political environments—face virtually the same kinds of workplace hazards. These hazards are traditionally categorized into four broad types: chemical, biological, physical, and psychosocial. What emerges from our incomplete knowledge of their risk, however, is that the more than 80 percent of the world's workforce that resides in the developing world disproportionately shares in the global burden of occupational disease and injury. Several classic occupational diseases, such as silicosis and lead poisoning, that have been substantially eliminated in industrial countries remain endemic elsewhere in the world. Whether this high and preventable burden of ill health faced by workers in the developing world is the result of ignorance, inattention, or intent, compelling evidence indicates that work-related health conditions could be substantially reduced, often at modest cost.