Which of the following describes LC50?

• A. Lethal Concentration for 50% of a population
• B. Lethal Dose for 50% of a population
• C. Lethality Constant at 50%
• D. Lethal Confusion at 50%

Answer: (A)

LC50 is the concentration of a toxicant in the environment that causes death in 50% of the test population during a defined exposure period. It’s a concentration, not a dose, and is typically expressed in units like mg/L. This measure reflects how lethal the medium is to organisms under specific conditions and exposure time. It differs from LD50, which describes the lethal dose per body weight when exposure is by ingestion or injection. The other terms aren’t standard toxicology measures—Lethal Dose for 50% would be LD50, and the phrases “Lethality Constant” or “Lethal Confusion” don’t correspond to recognized concepts.