All of the following have been associated with methyl mercury poisoning except:

Methyl mercury poisoning is primarily associated with the consumption of fish and seafood, particularly larger predatory fish that accumulate mercury in their tissues over time. Tuna, as a type of fish, is well-documented to have higher levels of methyl mercury due to its position in the food chain. Therefore, the correlation between tuna and methyl mercury poisoning is significant and widely recognized.

On the other hand, bread, pork, and fungicides are not typically linked with methyl mercury exposure. Bread is generally not a source of methyl mercury, while pork does not accumulate methyl mercury to the same extent as fish. Fungicides might have their own health implications, but they do not relate to methyl mercury poisoning.

This distinction makes it clear that tuna is a known source of methyl mercury, while the others are not associated with this type of poisoning.