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Mercury in Fish: Does Eating Seafood Help or Harm Your Health?

Government and industry fail to educate and protect consumers from seafood risks


Woman eating nigiri sushi
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The next time you start to order a tuna sandwich for lunch or a swordfish steak as your dinner entrée, give some thought to a research study by the Chicago Tribune and Rutgers University, which shows that commercial seafood contains much higher levels of mercury than most people suspect.

The Health Risks of Mercury in Seafood
Mercury is a highly toxic heavy metal that can damage the central nervous system of children and unborn fetuses, slowing development of walking and talking and decreasing memory and attention span. Adults may experience headaches, fatigue, lack of concentration, and numbness in their hands and feet. According to the newspaper, some studies suggest that men may face an increased risk of heart attack.

The investigation by the Tribune also found that government regulators and the seafood industry are doing little to protect public health and, in fact, have been placing consumers at risk for decades by “knowingly allowing millions of Americans to eat seafood with unsafe levels of mercury.”

Government Downplays Dangers of Mercury in Seafood
Through extensive interviews and a review of government records, the newspaper discovered that “regulators have repeatedly downplayed the hazards, failed to take basic steps to protect public health and misled consumers about the true dangers” of eating seafood containing mercury.

According to the Tribune the government does not confiscate fish that exceed U.S. mercury limits, and regulators don’t regularly inspect seafood for mercury at any point between the boat and the dinner plate. For example, the newspaper found that the government has tested only four walleye and 24 shrimp samples since 1978. As a result, federal officials have only a limited idea of how much mercury most species contain.

Mercury is now pervasive in all of the world’s oceans, lakes and streams, deposited there by air pollution, and all fish contain some level of the toxic substance, so it is virtually impossible to eat fish without ingesting some mercury.

Eating Fish is Good for You
At the same time, medical experts agree that eating seafood is good for most people, because it carries many health benefits. Seafood is a low-fat source of protein. Some fish, such as salmon, are rich in omega-3 acids, which promote good health and help to prevent heart disease. Largely as a result of that message, per capita seafood consumption in the U.S. is at an all-time high.

So, how can consumers get the health benefits of seafood without the placing themselves at high risk of mercury contamination? The first step is to understand how mercury accumulates in fish.

How Does Mercury Accumulate in Fish?
Mercury is released into the air as a byproduct of certain industrial processes. From there, it ends up in oceans, lakes and water, sometimes drifting thousands of miles before descending. This makes mercury a global environmental problem, because a factory Asia or Europe could contaminate a lake in the U.S., or vice versa.

Once mercury enters the water, bacteria there chemically alter the mercury, creating a highly toxic substance called methylmercury. Small fish eat or absorb the methylmercury and are eaten in turn by bigger fish, which are then eaten by even bigger fish. As mercury moves up the food chain, it accumulates. As a result, larger predator fish, such as sharks and swordfish, tend to contain higher levels of mercury than salmon and other fish farther down the food chain.

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