Canned tuna contains minute amounts of methylmercury. According to surveys conducted by FDA, canned light tuna has an average of 0.12 parts per million (ppm) and canned albacore tuna has an average of 0.35 ppm. To put these amounts into perspective, FDA has set a limit of 1.00 ppm for mercury in fish - and both canned light and albacore tuna are well below this level.