Which statement is true about the LD50 and LC50?

• A. Both measure acute toxicity
• B. Both measure chronic toxicity
• C. LD50 measures chronic toxicity; LC50 measures environmental fate
• D. They measure dose rate

Answer: (A)

LD50 and LC50 measure acute toxicity. They indicate the amount (LD50) or concentration (LC50) of a substance that will kill 50% of a test population within a short, defined exposure period. This makes them about short-term lethal effects, not long-term or chronic outcomes. They don’t assess chronic toxicity, environmental fate, or dose rate—the values are thresholds for lethality in a brief exposure window.