What does LD50 represent?

What does LD50 represent?

• A. The amount required to kill 50% of test population by either oral or dermal exposure
• B. The concentration in air required to kill 50%
• C. The amount that will cause death in 100% of test population
• D. The amount causing any effect in 50% of tests

Answer: (A)

LD50 is a measure of acute toxicity that tells you the dose of a chemical likely to kill 50% of a test population when exposure occurs by a specific route, typically oral or dermal. It is usually expressed per body weight (for example, milligrams of chemical per kilogram of body weight), so it provides a size-adjusted estimate of how potent the substance is. The smaller the LD50, the more toxic the chemical is via that route. This concept is about dose, not concentration in air, and it’s separate from LD100 (death in all) or ED50 (the dose producing a given effect in 50%). LD50 also depends on the species, sex, and test conditions, so it’s a comparative tool rather than a universal constant.