The amount of an ingested or injected substance that results in the death of 50% of the test population is:

• A. LC-50
• B. LD-50
• C. LD-10
• D. LC-99

Answer: (B)

Understanding lethal dose metrics: LD-50 is the amount of a substance that, when ingested or injected, would kill 50% of the exposed population. It’s a standard measure of acute toxicity used to compare how potent different substances are, though the exact value depends on species, route of exposure, and conditions. Inhalation uses LC-50, the lethal concentration in air for 50% of those exposed. Other thresholds include LD-10 (lethal to 10%) and LC-99 (lethal to 99% via inhalation). Therefore, the description in the question matches LD-50 because it specifies the ingestion/injection route and a 50% mortality rate.