LC50 is defined as which of the following?

LC50 is defined as which of the following?

• A. Concentration of a pesticide in the air which would kill half of the test animals exposed to it
• B. An amount of pesticide causing immediate death after a single exposure
• C. Total amount of pesticide present in air at a given time
• D. The concentration of pesticide that causes skin irritation in 50% of people

Answer: (A)

LC50 is the concentration of a substance that would kill 50% of exposed test animals under defined conditions. In inhalation terms, it’s the amount in the air (mg per cubic meter or ppm) that causes death in half the subjects after a specified exposure time. This measure reflects potency—the lower the LC50, the more toxic the pesticide is, because less exposure is needed to reach the lethal endpoint. The option described matches this concept precisely: it focuses on a lethal outcome for 50% of the exposed population in the air. The other ideas refer to different toxicity endpoints or non-lethal effects: immediate death after a single exposure is more like an LD50 or acute toxicity metric, total pesticide amount in the air is about environmental concentration rather than lethality, and irritation thresholds concern skin effects rather than mortality.

LC50 is the concentration of a substance that would kill 50% of exposed test animals under defined conditions. In inhalation terms, it’s the amount in the air (mg per cubic meter or ppm) that causes death in half the subjects after a specified exposure time. This measure reflects potency—the lower the LC50, the more toxic the pesticide is, because less exposure is needed to reach the lethal endpoint. The option described matches this concept precisely: it focuses on a lethal outcome for 50% of the exposed population in the air. The other ideas refer to different toxicity endpoints or non-lethal effects: immediate death after a single exposure is more like an LD50 or acute toxicity metric, total pesticide amount in the air is about environmental concentration rather than lethality, and irritation thresholds concern skin effects rather than mortality.