LC50 and LD50 refer to what type of measurement?

• A. LD50 is the lethal dose that kills 50% of animals exposed.
• B. LC50 is the lethal concentration that kills 50% of animals exposed.
• C. LD50 describes the speed of death.
• D. LC50 describes the dose required to kill all animals.

Answer: (B)

In toxicology, LC50 and LD50 are median lethal toxicity measures. They describe the amount of a substance needed to cause death in 50% of a test population. LC50 uses concentration in the exposure medium (for example, mg of substance per liter of air or water) to define the lethal level, while LD50 uses the dose per body weight (mg per kg) delivered to the animal. The statement that LC50 is the lethal concentration that kills 50% of animals exposed captures this concept directly, since it focuses on the exposure concentration rather than a dose per body weight. These metrics compare how potent a toxin is, and they don’t convey speed of death or imply that all animals are killed.