Toxicity from eating contaminated fish:
This is one of the main sources of mercury poisoning and one which is attracting a great deal of recent attention. The FDA is coming under increasing pressure from environmental groups to warn the public of the dangers of eating tuna because it contains enough mercury to damage a developing foetus. At least three states, Washington, New Jersey and Minnesota, have recommended pregnant women to limit tuna consumption to 1 1/2 cans per week, and in Canada and advisory was issued warning women of childbearing age and children to limit consumption of shark, swordfish and fresh tuna to one meal per month.
The FDA since 2001 had already advised pregnant women, women who may become pregnant, and small children to avoid eating four types of fish: shark, swordfish, king mackerel and tilefish. However, tuna was not on the list of fish to avoid and the FDA recommendations that up to 12 ounces or 2 1/2 cans of tuna per week is safe to eat is being challenged by the environment working group.
It is important to note that not all fish are considered risky in the context of mercury contamination. Fish is high in omega-3 polyunsaturated fatty acids which is known to be beneficial to cardiovascular health. Therefore, rather than avoid all fish, it is more prudent to find good substitutes for the risky fish. There are many types of fish available and farm raised fish is one option. Only trace amounts of mercury, 40-100 times below the safe limit were found in common commercially produced fish.