An occupational hazard is a thing or situation with the potential to harm a worker. Occupational hazards can be divided into two categories: safety hazards that cause accidents that physically injure workers, and health hazards which result in the development of the disease. It is important to note that a “hazard” only represents the potential to cause harm. Whether it does cause harm will depend on circumstances, such as the toxicity of the health hazard, exposure amount, and duration. Hazards can also be rated according to the severity of the harm they cause – a significant hazard being one with the potential to cause a critical injury or death.