Pesticides from class '1B highly hazardous' have LD50 for the rat (oral) in which range?

• A. 50-500 mg/kg BW
• B. 5-50 mg/kg BW
• C. Over 500 mg/kg BW
• D. 0.5-5 mg/kg BW

Answer: (B)

Understanding how acute toxicity is categorized by LD50 helps interpret this item. LD50 is the dose, per kilogram of body weight, that would kill 50% of a tested animal population after exposure by a specific route, often oral in rats. A smaller LD50 means a more toxic chemical. For pesticides labeled as Class 1B highly hazardous, the oral LD50 in rats falls between 5 and 50 mg/kg. That range indicates high acute toxicity from ingestion, which is why these substances require strict safety measures and careful handling. If the LD50 were lower than 5 mg/kg, it would be in the more hazardous class, and if it were above 50 mg/kg, it would fall into a lower hazard category.