CPA Pesticide Toxicology and Mode of Action 2 — Questions and Answers
Question 1: Neonicotinoid insecticides such as imidacloprid act primarily on which receptor in insects?
- GABA-gated chloride channel
- Ryanodine receptor
- Nicotinic acetylcholine receptor (Correct answer)
- Voltage-gated sodium channel
Correct answer: Nicotinic acetylcholine receptor
Neonicotinoids bind to nicotinic acetylcholine receptors in insects, causing continuous nerve stimulation; they have much lower affinity for mammalian receptors.
Question 2: Which class of insecticides disrupts insect development by mimicking or interfering with juvenile hormone, preventing normal molting?
- Organochlorines
- Insect growth regulators (IGRs) (Correct answer)
- Pyrethroids
- Carbamates
Correct answer: Insect growth regulators (IGRs)
Insect growth regulators mimic juvenile hormone or ecdysone, disrupting molting and metamorphosis without the same risks to mammals as conventional neurotoxins.
Question 3: A 'systemic' pesticide is one that:
- Only kills pests through direct contact with the spray
- Is absorbed by the plant and translocated throughout its tissues (Correct answer)
- Degrades rapidly in soil without residual activity
- Only affects insects in the digestive tract
Correct answer: Is absorbed by the plant and translocated throughout its tissues
Systemic pesticides are absorbed by plant roots or leaves and move within plant vascular tissue, protecting parts not directly sprayed.
Question 4: What is the primary mode of action of organochlorine pesticides such as DDT?
- Acetylcholinesterase inhibition
- GABA receptor disruption
- Voltage-gated sodium channel disruption (Correct answer)
- Chitin synthesis inhibition
Correct answer: Voltage-gated sodium channel disruption
DDT and other organochlorines keep voltage-gated sodium channels open in nerve membranes, causing repetitive nerve firing similar to pyrethroids.
Question 5: Which EPA toxicity category requires both the signal word 'DANGER' and the word 'POISON' printed on the pesticide label?
- Category IV
- Category III
- Category II
- Category I (Correct answer)
Correct answer: Category I
Category I pesticides are the most acutely toxic and require 'DANGER' along with 'POISON' and a skull-and-crossbones symbol on the label.
Question 6: Bioaccumulation of pesticides in the food chain primarily occurs with compounds that are:
- Water soluble and rapidly degraded
- Lipophilic (fat-soluble) and environmentally persistent (Correct answer)
- Highly volatile and quickly lost to the atmosphere
- Rapidly metabolized in animal tissues
Correct answer: Lipophilic (fat-soluble) and environmentally persistent
Lipophilic, persistent pesticides like organochlorines accumulate in fatty tissues and concentrate through food chains via biomagnification.
Question 7: In pesticide toxicology, what does the term 'dermal absorption' specifically refer to?
- Pesticide entering the body through inhalation via the nose and lungs
- Pesticide ingested through the mouth and absorbed in the gut
- Pesticide penetrating through the skin and entering the bloodstream (Correct answer)
- Pesticide entering the body through the eyes
Correct answer: Pesticide penetrating through the skin and entering the bloodstream
Dermal absorption is the process by which pesticides penetrate the skin barrier and enter systemic circulation, making proper PPE and skin protection critical.
CPA Pesticide Toxicology and Mode of Action 2
Neonicotinoid insecticides such as imidacloprid act primarily on which receptor in insects?