The full environmental impact of the oil spill in the Gulf of Mexico won’t be known for a long time, but there is great fear that all sea life in the region will be severely affected, both by the oil and the chemicals used to disperse it. The systemic pollution of our lakes, rivers and oceans, of course, has long been of concern, and this recent disaster only adds to the stress the fish and wildlife population is already exposed to. Not surprisingly, we ourselves are bound to ingest the poisonous substances we keep releasing into the environment through our food and especially our seafood.
One of the most common pollutants found in seafood is mercury. In one survey conducted in New York City, seafood dishes from twenty restaurants and sushi bars were tested for mercury content. The results were outright alarming. More than a quarter of the tested items exceeded not only the limits recommended by the Food and Drug Administration (F.D.A.), they qualified as hazardous enough to be removed from the market by legal action. Since a federal testing program for mercury does not exist, the contamination of seafood sold in the United States remains generally unknown. But there is no reason to assume that the findings of this investigation are limited to New York.
What is mercury?
Mercury is a metal found in soil and rock, but it is also released into the air and the water, mostly through industrial pollution and waste. When mercury gets in contact with water, it forms a toxin called methylmercury, which then is absorbed over time by tiny organisms.
How does mercury get into fish?
All fish species eat these organisms, whether they live in freshwater or in the ocean. Unfortunately, mercury cannot easily be eliminated through the digestive system. Instead, it accumulates and gradually poisons the animals. Larger carnivore fish species ingest the toxins of their prey as well. Consequently, the largest and longest living fish on top of the food chain have the highest concentration of pollutants, including mercury.
What makes mercury dangerous?
There is scientific evidence that elevated levels of mercury adversely affect the nerve cells in the brain and spinal cord. High doses may also cause damage to the digestive system and the kidneys. Children are at higher risk than adults. Because mercury passes through the placenta, it can be especially harmful to fetuses. For that matter, women who are pregnant or plan to get pregnant should exercise extra caution and reduce their seafood consumption if necessary.
Not all fish has the same level of toxins
The larger a fish grows and the longer it lives, the more it is exposed to toxins. Shark, tilefish, king mackerel, swordfish and sturgeon fit in this category and should be avoided or eaten only rarely and in small portions. More recently, the bluefin tuna has also been added to the list of seafood too contaminated for frequent consumption. Moreover, wild bluefin tuna is facing worldwide extinction and may not be available for much longer if demand remains high.
Tuna cuts used in sushi generally contain higher levels of mercury than other fish species. The consumption of raw tuna should be limited to one or two pieces per week or less. Better sushi choices with regards to mercury contamination are salmon, squid, octopus, and eel. It is considered safe to eat up to 12 ounces (two servings) of cooked fish per week, such as salmon, cod, shellfish, pollock, haddock, tilapia, sole, snapper and catfish.
What to look for in fish
It is advisable to buy fish only from reputable sources. Freshness and proper storage are most important. Avoid fish that looks slimy, dried out or has blood spots and other blemishes. Reassuring indicators are clear eyes and bright red gills. Fish is highly perishable and must be kept refrigerated, even during defrosting. “Wild caught” is still preferable to farmed fish, although, it may only be a question of time until most available seafood will be farmed. Thankfully, organic fish farming methods are on the rise.
Despite of all the bad news about environmental pollution affecting our food supplies, it must be said that the health benefits of eating seafood still outweigh the downsides. Seafood is a great provider of lean protein. Specific health benefits come from fish oil, which is rich in omega-3 fatty acids. There is general agreement among the experts that including fish in one’s diet can significantly lower the risk of heart disease and stroke. In other words, seafood is an important component of a healthy diet and deserves our protection as a vital resource.