Which of the following foods is NOT commonly associated with mercury poisoning?

The food that is not commonly associated with mercury poisoning is shelled nuts. Mercury is a heavy metal that accumulates in aquatic systems, particularly in fish and shellfish. Contaminated fish and shellfish are significant sources of methylmercury, the organic form of mercury that is most harmful to human health.

Fish, especially larger predatory species like tuna and swordfish, can contain high levels of mercury due to their position in the aquatic food chain, where they accumulate mercury by feeding on smaller fish that have also absorbed mercury from their environment. Shellfish, while usually lower in mercury, can still accumulate this heavy metal depending on their habitat and diet.

In contrast, shelled nuts are terrestrial food items that do not come into contact with water sources where mercury typically accumulates. Therefore, they are not a source of mercury poisoning, making them the correct answer in this context. Pork, being an animal protein, also does not have the same association with mercury, but the risk is much lower compared to that of fish and shellfish.