True or False: Acute toxicity is measured as the amount or concentration of a toxicant required to kill 50 percent of test animals, expressed as LD50 or LC50.

• A. True
• B. False
• C. Not sure
• D. Sometimes

Answer: (A)

Acute toxicity is assessed by the dose or concentration that causes death in a portion of animals after a short-term exposure, and the standard way to express this is with LD50 or LC50. LD50 refers to the lethal dose for 50% of the test animals and is used for doses taken by ingestion or dermal exposure, while LC50 is the lethal concentration for 50% exposed via inhalation. The smaller these values, the more acutely toxic the substance is. This measure helps compare hazards among pesticides and informs labeling, handling, and safety precautions. Note that other concepts cover long-term effects (chronic toxicity) and use different metrics, but for acute toxicity the LD50/LC50 framework is the standard.