What does LD50 tell toxicologists when comparing two chemicals?

• A. The chemical with the lower LD50 is more toxic
• B. The chemical with the higher LD50 is more toxic
• C. LD50 cannot be used to compare toxicity
• D. LD50 indicates chronic toxicity

Answer: (A)

LD50 is the dose that kills 50% of a test population under specific conditions, reflecting how much of a chemical is needed to be lethal in acute exposure. Because it represents the amount required to produce death in half the subjects, a smaller LD50 means the chemical is more toxic. So when comparing two chemicals, the one with the lower LD50 is the more toxic in terms of acute toxicity. Remember, LD50 measures acute toxicity and is influenced by route of exposure and species, so it doesn’t address chronic toxicity.