Which statement about LC50 is incorrect?

• A. LC50 is the dose that kills 50% of test organisms
• B. A lower LC50 indicates greater toxicity
• C. LC50 is a measure of acute toxicity
• D. It measures the time to death in 50% of subjects

Answer: (D)

The main idea is what LC50 represents: the lethal concentration of a substance that kills 50% of the test organisms within a defined exposure period. It is a measure of acute toxicity, tied to how much of the substance is present in the environment, not how long it takes for individuals to die. Because a smaller concentration is enough to cause death in half the population, a lower LC50 indicates greater toxicity. The statement claiming LC50 measures the time to death in 50% of subjects is the one that’s incorrect—it would be a metric like LT50 (lethal time), not LC50. Different LC50 values can be reported for different exposure durations (24, 48, 96 hours), but LC50 always reflects concentration leading to 50% mortality, not the time until death.