Which statement about pesticide toxicity is true?

• A. A pesticide with an oral LD50 of 5 mg/kg is more toxic than a pesticide with an LD50 of 250 mg/kg
• B. A pesticide with an oral LD50 of 250 mg/kg is more toxic than one with 5 mg/kg
• C. LD50 values do not relate to toxicity
• D. LD50 values only apply to topical exposure

Answer: (A)

LD50 is a standard measure of acute toxicity that tells you how much of a pesticide, given by a specific route, is needed to kill 50% of a test population. The smaller the LD50 number, the more toxic the substance is because only a tiny amount is enough to cause death in half the animals. So, an oral LD50 of 5 mg/kg means it takes only 5 milligrams per kilogram of body weight to reach that level of lethality, which is far more toxic than a substance with an oral LD50 of 250 mg/kg.

LD50 values are indeed related to toxicity, and they are specific to the route of exposure. They’re not universal across all exposure routes, and they don’t capture chronic effects—just acute toxicity for that route. They also aren’t limited to topical exposure.