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Pluton poisoning is a form of radiation that breaks down the proteins in food, thus rendering it a useless, incompatible foodstuff. Typically, this is the result of fallout from pluton bombs.
Pluton poisoning affects a bulk of the food supply after the Fleet makes their exodus from the now-Cylon-held Twelve Colonies. Jolly detects the poisoning (TOS: "Saga of a Star World").