Final answer:
Exposure to high concentrations of organophosphate insecticides, if untreated, usually results in death due to respiratory failure caused by overaccumulation of acetylcholine and failure of respiratory muscles.
Step-by-step explanation:
A crop duster pilot exposed to a high concentration of a highly toxic agricultural organophosphate insecticide, if untreated, would most likely die from respiratory failure. Organophosphates, which are related to nerve agents developed during World War II, inhibit the enzyme acetylcholinesterase, leading to an overaccumulation of acetylcholine. This causes prolonged muscle contraction, eventually causing respiratory muscles to fail, preventing breathing and leading to asphyxiation.
The symptoms of poisoning by a nerve agent, which include organophosphates like parathion, characteristically lead to profuse salivation, convulsions, involuntary urination and defecation. Death may follow quickly by asphyxiation or cardiac arrest due to loss of control over respiratory muscles.