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Mercury & Fish:
What You Need to Know

Jan Erik Gjestvang-Lucky

Even though my wife and I are vegetarians, we have been considering feeding meat or seafood to our almost 17-month-old son. Why? Because he can be picky about what he eats, and we want to make sure he is getting enough protein to support his growth. We also want to make sure he gets enough essential fatty acids for proper brain development. In other words, we want him to be smart and strong and healthy.

According to the U.S. Tuna Foundation, canned albacore tuna, also known as white tuna, would be the perfect thing: “...with the exception of salmon, canned albacore tuna contains more DHA than any other commonly eaten seafood.” DHA (docosahexaenoic acid) is a fatty acid that is essential for normal visual and neurological development in infants from pregnancy through the first two years of life. Sounds great: eat tuna and get good brain food, for you and your baby. What the website doesn’t mention, however, is that many experts believe there are good reasons for pregnant women and children to avoid eating albacore altogether. Some also say that everyone should be concerned, and not just about tuna, but about all fish they eat. Why are they saying this? Because much of the fish we eat may be contaminated with mercury.

Where does this mercury come from?
The Mercury Policy Project says, “The majority of the mercury entering lakes, streams, rivers, and oceans comes from the atmosphere. Eighty-five percent of all mercury pollution in the U.S. is released by power plants burning coal and municipal and medical waste incinerators burning mercury tainted trash.” In Wisconsin, the largest source of mercury emissions is Vulcan Materials Company in Port Edwards, a chlorine producer, though most of the state’s other top twenty mercury polluters are coal burning power plants. Mercury emissions can be carried on the wind to areas hundreds of miles from their sources. They then enter our waters in the form of rain or snow. This is how even remote waters, once considered pristine, can become contaminated.

Once in the water, mercury is transformed by bacteria into methyl mercury, an organic form of mercury that is very easy for humans to absorb, and extremely toxic. It is also easily absorbed by aquatic plants and fish directly from the water. Smaller fish eat those plants, and larger fish eat those fish, gradually accumulating more and more mercury. The older the fish and the higher up the food chain it is, the more mercury it is likely to have. And this doesn’t just happen with seafood; freshwater fish can also be contaminated.

Wisconsin’s Department of Natural resources has issued mercury related fish consumption advisories for all of its 15,000 lakes, and 57,000 miles of rivers and streams. So it doesn’t seem to matter where our fish comes from, it is still likely to be contaminated by mercury.

Why is mercury contamination a problem?
Mercury is a poison; specifically, it is a neurotoxin. It can permanently damage the brain and nervous system, not only in developing fetuses and infants, but also in older children and adults. A Centers for Disease Control and Prevention (CDC) estimate says that one in six women of childbearing age have high enough blood mercury levels to damage a developing fetus. This means that at least 630,000 babies born in the U.S. each year have high enough mercury levels to cause irreversible neurological damage. This can take the form of developmental delays, cerebral palsy, deafness, and blindness. Studies on prenatal mercury exposure have shown that these effects are still noticeable seven, and even fifteen, years later. Infants and children with mercury poisoning can have lower IQs, learning disorders and attention deficit problems, and delays in walking and speaking. Adults aren’t immune either; their symptoms can include memory loss, tremors, vision problems, and numbness in fingers and toes, as well as problems with fertility and blood pressure. One of our country’s biggest killers, heart disease, has also recently been linked to mercury poisoning.

So, how much mercury is too much?
This is a question with very different answers, depending on your perspective, which may, in turn, depend on your employer. The Food and Drug Administration’s (FDA) current action level for mercury in fish (the level of contamination at which the FDA can take legal action to remove that fish from the market) is 1.0 parts per million (ppm). This amount was set in 1979, and is twice as high as the original level, set in 1969, of 0.5 ppm. The tuna industry claims this standard of 1.0 ppm reflects safety factor of more than ten, meaning it is ten times less than the lowest level of mercury ever known to have negative effects on humans. The FDA currently says that it is safe to eat two cans, or six ounces, of tuna per week, or one six-ounce can of albacore tuna. The Environmental Protection Agency (EPA) has established a maximum safe level for mercury ingestion of 0.1 micrograms per day for each kilogram of bodyweight. One microgram is one millionth of a gram, and a kilogram is about 2.2 pounds. One can of albacore, the same kind promoted as good brain food by the U.S. Tuna foundation, would give a 150 pound woman one-and-a-half times the maximum safe level of mercury. If a five year old child weighing 40 pounds ate one can of albacore per week, s/he would get FIVE TIMES the EPA safe level. Even though the tuna industry, the EPA, and the FDA all refer to “safe” levels of mercury, recent research suggests that there may be NO safe level for such a potent poison as mercury. In other words, mercury may show negative effects on the brain and nervous system across the normal range of exposure for humans, even when it is well below the current standards for safety. As Stephanie Cave, M.D., an expert in mercury toxicity in children, said, “What is a safe level of a poison?”

What can you do to protect yourself?
As with most questions relating to health and the environment, the answer is multifaceted. The most obvious thing to do is limit your fish intake, making sure to inform yourself about which fish are most likely to have more mercury. Although mercury does build up in the body over time, it is possible to reverse that buildup, and lower blood mercury levels, by reducing or eliminating the amount of mercury-contaminated fish consumed. You can leave it at that, or you can take action by working to reduce mercury pollution at its source.

The Clean Air act became law in 1970, but its provisions for reducing mercury emissions have been severely undermined by rule changes in the last two years. Almost a decade ago, the EPA determined that it would be possible to reduce mercury emissions from coal power plants by 90 percent in three years. With the weakened Clean Air Act, it could now take fifteen years just to get a 30 percent reduction in mercury emissions. The new rules would also allow heavy polluters to buy credits from cleaner plants, allowing them to keep polluting at high levels. This would leave the communities of the dirty plants exposed to dangerous amounts of mercury. As long as this keeps happening, our waterways and fish will continue to be poisoned by mercury.

Some organizations to look at for information and action suggestions are: The Mercury Policy Project (, MoveOn (, and the National Resources Defense Council ( This page, from the website for NOW with Bill Moyers, also has good information: Here is the website for the FDA/EPA joint advisory on mercury in fish: For balance, make sure to check out The U.S. Tuna Foundation (