TD50 refers to the dose causing toxic effects in 50% of the population, while LD50 refers to the lethal dose in 50% of the population. Which statement is true?

TD50 refers to the dose causing toxic effects in 50% of the population, while LD50 refers to the lethal dose in 50% of the population. Which statement is true?

• A. TD50 describes toxic effects in 50% and LD50 describes lethal dose in 50%
• B. TD50 describes lethal dose, LD50 describes toxic effects
• C. TD50 and LD50 describe the same endpoint
• D. LD50 describes chronic toxicity

Answer: (A)

TD50 and LD50 describe two different dose-response endpoints in toxicology. TD50 is the dose at which 50% of subjects experience toxic effects—adverse health effects that aren’t necessarily fatal. LD50 is the dose that causes death in 50% of subjects, reflecting acute lethality after exposure. The statement is true because it correctly assigns each endpoint to its corresponding effect: toxic effects for TD50 and death for LD50. This distinction matters because a substance can produce toxicity without being lethal at certain doses, and LD50 specifically refers to an acute, lethal outcome rather than chronic toxicity, which is evaluated by other measures. The other ideas mix up the endpoints or confuse acute lethality with chronic toxicity, so they don’t fit.

TD50 and LD50 describe two different dose-response endpoints in toxicology. TD50 is the dose at which 50% of subjects experience toxic effects—adverse health effects that aren’t necessarily fatal. LD50 is the dose that causes death in 50% of subjects, reflecting acute lethality after exposure. The statement is true because it correctly assigns each endpoint to its corresponding effect: toxic effects for TD50 and death for LD50. This distinction matters because a substance can produce toxicity without being lethal at certain doses, and LD50 specifically refers to an acute, lethal outcome rather than chronic toxicity, which is evaluated by other measures. The other ideas mix up the endpoints or confuse acute lethality with chronic toxicity, so they don’t fit.