Question 1: Which of the following is the least toxic organophosphorus compound?
- A. Parathion
- B. Malathion
- C. Fenitrothion
- D. Abate (Correct Answer)
Explanation: ***Abate (Temephos)***
- **Abate** is specifically designed for use in water as a mosquito larvicide and has a notably **lower mammalian toxicity** compared to other organophosphates.
- Its chemical structure and metabolic breakdown in mammals make it less potent in inhibiting **acetylcholinesterase**.
*Malathion*
- While generally considered less toxic than some other organophosphates like parathion, **malathion** still poses significant toxicity, especially with **high or prolonged exposure**.
- It is metabolically activated to **malaoxon**, a more potent acetylcholinesterase inhibitor.
*Fenitrothion*
- **Fenitrothion** is an organophosphate insecticide with moderate to high toxicity, similar to malathion, but often considered more toxic for some species.
- It works by inhibiting **cholinesterase enzymes**, leading to a buildup of acetylcholine.
*Parathion*
- **Parathion** is one of the most highly toxic organophosphorus compounds, historically used as a powerful insecticide but now restricted or banned in many countries due to its severe toxicity.
- It is readily absorbed and metabolically converted to **paraoxon**, a very potent cholinesterase inhibitor.