The LD₅₀ values of some pesticides are listed below. Which of the following is most toxic?

Correct option is B

LD₅₀ (Lethal Dose 50%) is the dose of a substance required to kill 50% of a test population, usually expressed in mg/kg of body weight. A lower LD₅₀ value indicates higher toxicity.
Comparison of the given options:
1. DDT (110 mg/kg):
· Moderately toxic.
· Long-lasting persistence in the environment but less toxic compared to Parathion and Nicotine.
2. Parathion (<5 mg/kg):
· Highly toxic.
· Extremely low LD₅₀ makes it the most toxic among the options. It inhibits acetylcholinesterase, causing severe neurological effects.
3. Permethrin (50-500 mg/kg):
· Low to moderate toxicity.
· Widely used as an insecticide, particularly in agricultural and residential applications.
4. Nicotine (5-50 mg/kg):
· Highly toxic.
· A potent neurotoxin affecting the nervous system, but its LD₅₀ range is higher than Parathion.
Information Booster: 1. LD₅₀ Classification of Toxicity (Approx.):
· <5 mg/kg: Extremely toxic (e.g., Parathion).
· 5-50 mg/kg: Highly toxic (e.g., Nicotine).
· 50-500 mg/kg: Moderately toxic (e.g., Permethrin).
· 500-5000 mg/kg: Slightly toxic.
2. Environmental Implications:
· Persistent substances like DDT pose ecological risks even with moderate toxicity.
· Highly toxic substances like Parathion require stringent handling and regulation.
3. Safe Handling of Pesticides:
· Use protective equipment.
· Follow guidelines for application and storage.