What does LC50 mean?

• A. The lethal dose for 50% of test animals
• B. The concentration of pesticide in the air that must be present to kill 50% of test animals
• C. The dose required to kill 50% via dermal exposure
• D. The amount needed to cause 50% of tests to show any effect

Answer: (B)

LC50 is the concentration of a pesticide in the exposure environment that will kill 50% of the test animals under defined conditions. It’s used for inhalation (air) or aquatic exposures, so it’s expressed as a concentration (like parts per million in air or mg/L in water), not as a dose per animal. This distinguishes it from LD50, which is the lethal dose per animal. The statement describing the concentration in air needed to kill 50% of the test animals matches this definition, making it the correct interpretation. The other ideas refer to dose per animal, dermal exposure, or nonlethal effects, which are not what LC50 measures.