Associate Certified Entomologist (ACE) Practice Exam

What does LD50 signify in toxicology?

1. Amount needed to kill 50% of a population from exposure

2. Amount needed to kill all animals in a population

3. Amount required for therapeutic effect

4. Amount that can be safely ingested

The correct answer is: Amount needed to kill 50% of a population from exposure

LD50 stands for "lethal dose for 50 percent," which is a standard measure used in toxicology to indicate the dose of a substance required to kill half of a tested population, typically within a specified timeframe. This metric is important because it quantifies the toxicity of a substance and allows comparisons between different compounds. By determining the LD50 value, researchers and toxicologists can assess the relative risk or safety of a substance, which is crucial for regulatory purposes and public health. The lower the LD50 value, the more toxic the substance is considered, as it indicates that a smaller amount is needed to cause death in half the population. The other options do not accurately capture the definition or use of LD50 in toxicology. For instance, the idea of a dose that kills all animals in a population would not be relevant to LD50, as it specifically pertains to the death of half of the population. Similarly, the concepts of therapeutic effects or safe ingestion levels do not align with the lethal dose measurement that LD50 represents.