HAZMAT Technician Practice Exam

What does LC50 indicate?

1. The lethal concentration of a chemical in water

2. The concentration of a substance sufficient to kill 50% of test subjects

3. The volume of air contaminated by a toxic gas

4. The level of exposure allowed for a worker

The correct answer is: The concentration of a substance sufficient to kill 50% of test subjects

LC50, or Lethal Concentration 50, specifically refers to the concentration of a substance in air or water that is lethal to 50% of a defined test population, typically laboratory animals. This measurement is crucial in toxicology as it provides a quantitative assessment of the toxicity of a substance, allowing researchers and safety professionals to gauge the potential risk it poses to living organisms. By establishing this value, one can compare the toxicity of various chemicals and understand their hazard potential in an environmental or occupational setting. Other options do not accurately capture the essence of what LC50 represents. While lethal concentration in water is a related concept, the correct definition encompasses both air and water assessments. The volume of air contaminated by a toxic gas refers to different metrics and does not address the concept of LC50 directly. Similarly, acceptable exposure levels for workers pertain to regulatory standards and guidelines rather than the specific measurement of lethality defined by LC50. Thus, understanding LC50 is vital for evaluating chemical hazards and ensuring safety measures are appropriately applied in relevant environments.