What are common characteristics of pyrethroid pesticides?

• A. They are growth regulators affecting mammalian nervous system.
• B. Disinfectants used on water supplies.
• C. Insecticides that act on nervous system; commonly fast knockdown; relatively low mammalian toxicity; potential for resistance.
• D. They are attractants used for baiting pests.

Answer: (C)

Pyrethroids are insecticides that affect the insect nervous system, producing rapid knockdown. They work by altering voltage-gated sodium channels in nerve cells, causing nerves to fire repeatedly and pests to be paralyzed quickly. This mechanism explains the fast control you often observe after exposure. They are favored for their relatively low mammalian toxicity, since mammals metabolize and detoxify these compounds more efficiently and their nervous system is less affected by the same mode of action. But insects can develop resistance through changes in the sodium channel target (making it less sensitive) or through enhanced detoxification by enzymes, which reduces effectiveness over time. The other descriptions don’t fit pyrethroids: growth regulators, disinfectants for water, and attractants for baiting aren’t characteristics of this pesticide class.