An environmental group, Defenders of Wildlife, says it has conducted a study that has revealed high levels of mercury in imported tuna.
The highest levels were found in tuna from Ecuador and Mexico, which are known for catching more mature fish.
Tuna from Asia have the lowest levels, and tuna from the U-S generally has lower mercury levels than imported varieties.
High mercury levels have been linked to kidney damage and learning disabilities.
The U-S Food and Drug Administration says it's safe to eat two meals a week of tuna which is lower in mercury... like canned light tuna.
