LD50 is defined as what?

LD50 is defined as what?

• A. The dose or amount of pesticide which would kill half a large number of test animals if eaten or absorbed through the skin
• B. The concentration of pesticide in air causing 50% mortality
• C. The time needed for a pesticide to become inactive in the environment
• D. The maximum safe daily dose for humans

Answer: (A)

The concept being tested is how toxicity is quantified using a median lethal dose. LD50 represents the dose of a substance that would kill 50% of a test population, typically measured for a specific exposure route (such as ingestion or dermal contact) and expressed per unit of body weight (like mg per kg). This makes LD50 a direct measure of how much of the pesticide is needed to reach lethal effects in half the animals tested, so a lower LD50 means the substance is more toxic. That description matches the idea of a dose of pesticide that would kill half the animals when ingested or absorbed through the skin. The other options describe different concepts: a concentration in air causing 50% mortality is LC50, not LD50; the time for pesticide inactivity relates to environmental persistence; and the maximum safe daily dose is a different regulatory metric (often an acceptable daily intake or reference dose).

The concept being tested is how toxicity is quantified using a median lethal dose. LD50 represents the dose of a substance that would kill 50% of a test population, typically measured for a specific exposure route (such as ingestion or dermal contact) and expressed per unit of body weight (like mg per kg). This makes LD50 a direct measure of how much of the pesticide is needed to reach lethal effects in half the animals tested, so a lower LD50 means the substance is more toxic.

That description matches the idea of a dose of pesticide that would kill half the animals when ingested or absorbed through the skin. The other options describe different concepts: a concentration in air causing 50% mortality is LC50, not LD50; the time for pesticide inactivity relates to environmental persistence; and the maximum safe daily dose is a different regulatory metric (often an acceptable daily intake or reference dose).