In July, 2008, Knopf published my “Tuna: A Love Story.” I thought up the title and even designed the jacket. I was very proud of the title, until people started telling me that while it was clever, it didn’t come close to conveying what the book was about. “Tuna: A Love Story” could have been about anything: recipes, sushi, sandwiches, carpaccio, or even my reverence for the bluefin tuna, the fish whose portrait I painted for the cover. It was in fact about all those things, but upon looking at the title, no one would know that the book was also about biology, overfishing, mercury poisoning, fish-farming, the “tuna-dolphin problem,” and the possible extinction of the tuna. For the forthcoming paperback, the title has been changed to: “Tuna: Life, Death, and Mercury.”

In the original book, I discussed at some length the dangers of mercury in fish, especially tuna. I cited various studies, and concluded that while mercury is in fact poisonous to humans, the small amounts in bluefin tuna (the nominal subject of my love affair), probably wouldn’t harm anyone very much. The FDA warned pregnant women and nursing mothers against eating tuna, but everyone else could go right ahead and eat it. In fact, you probably should go right ahead and eat it, because fish is so good for you. It is an excellent source of lean protein and the omega-3 fatty acids that are essential for brain and eye development. It’s lower in cholesterol than most meats, and usually cheaper in the supermarket. The American Heart Association suggests eating at least two servings of oily fish every week to help keep your heart healthy. Bad idea.

book cover

Diagnosis: Mercury: Money, Politics & Poison

By Jane M. Hightower

Island Press, 326 pages

Buy the book

Mercury is so pervasively dangerous that it will probably do you more harm than good to eat certain kinds of fish regularly. Mercury is expelled by the ton from coal-fired electrical plants; it’s used in extracting gold from ore; it was used in hat-making (remember the Mad Hatter?); it’s used as a disinfectant (remember mercurochrome?) it’s in amalgam dental fillings; and thousands of tons were lost into the ocean when 16th-century Spanish treasure ships sank while transporting quicksilver (mercury) in one direction or the other between South America and Europe. And it’s used in the manufacture of chlorine.

In nature, chlorine is found in a combined state only, as sodium chloride (NaCl), common salt. It is a member of the halogen (salt-forming) group of elements and is obtained from chlorides by the action of oxidizing agents and more often by electrolysis. It is a greenish-yellow gas, combining directly with nearly all elements. It is widely used in making many everyday products, most importantly, safe drinking water. It is also extensively used in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, food, solvents, paints, plastics and many other consumer products. Chlorine is used in the manufacture of chlorinated compounds for sanitation, pulp bleaching, disinfectants and textile processing. Further applications are the manufacture of chlorates, chloroform, carbon tetrachloride and in the extraction of bromine. In other words, chlorine is used everywhere, and the manufactory has long been one of the primary sources of mercury’s release into the environment.

According to a recent study by the advocacy group Oceana, there are still some factories where chlorine is still being produced in a way that “creates numerous tons of mercury wastes with associated disposal and cleanup problems, pumps up corporate electric bills, unnecessarily, and in some cases turns neighboring communities against the companies.” Oceana identifies five American chlorine plants (“the filthy five”) in Ohio, Tennessee, Georgia, West Virginia and Wisconsin, that have not converted to the mercury-free technology now used in caustic soda plants around the world (including 36 in Japan) to reduce mercury contamination of the atmosphere. Caustic soda (sodium hydroxide, NaOH) is an important ingredient in the pulp and paper industries: the production of textile dyes, soap, detergents, solvents and herbicides.

For hundreds of years, mercury was prescribed as a cure for syphilis, but there is little evidence that it worked; indeed, it probably hurt more than it helped. In his 1874 “Materia Medica” (a book describing the uses of various substances in medicine), Dr. John B. Biddle discussed the preparations of mercury that could be used to cure or ameliorate syphilis and various other diseases:

“While it retains the liquid or metallic state, mercury is inert; but when taken internally, it sometimes combines with oxygen in the alimentary canal, and this becomes active. In the state of vapor, it frequently proves injurious — in some instances exciting salvation, ulceration of the mouth; in others, inducing a peculiar affectation of the nervous system, termed shaking palsy (tremor mercurialis), which is often attended with loss of memory, vertigo, and other evidence of cerebral disturbance, and sometimes terminates fatally.”

Mercury was administered various ways, including orally and by rubbing it on the skin. One of the more curious methods was fumigation, in which the patient was placed in a closed box with his head sticking out; mercury was placed in the box and a fire was started under the box, which caused the mercury to vaporize. As we have seen, vaporizing mercury is one of the best ways to poison the patient. Indeed, some of the symptoms of syphilis — tremors, hearing loss, joint pain, forgetfulness and delirium — are much the same as those of mercury poisoning.

In his 1972 “History of Quicksilver,” Leonard Goldwater wrote that “The use of mercury in the treatment of syphilis may have been the most colossal hoax ever perpetrated in the history of a profession that has never been free of hoaxes.” Thus the application of quicksilver for patients suffering from syphilis gave rise to the saying, “A night in the arms of Venus leads to a lifetime on Mercury.” The following information comes directly the U.S. Environmental Protection Agency’s Web site:

“Mercury is a naturally occurring element that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Pure mercury is a liquid metal, sometimes referred to as quicksilver that volatizes readily. When coal is burned, mercury is released into the environment. Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for over 40 percent of all domestic human-caused mercury emissions. EPA has estimated that about one-quarter of U.S. emissions from coal-burning power plants are deposited within the contiguous U.S. and the remainder enters the global cycle. Burning hazardous wastes, producing chlorine, breaking mercury products, and spilling mercury, as well as the improper treatment and disposal of products or wastes containing mercury, can also release it into the environment.

book cover

Diagnosis: Mercury: Money, Politics & Poison

By Jane M. Hightower

Island Press, 326 pages

Buy the book

“Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others. The levels of methylmercury in fish and shellfish depend on what they eat, how long they live and how high they are in the food chain.”

Mercury begins its journey upward from the moment it lands on the bottom of the sea (or a river or lake), where it is absorbed by bacteria and converted to methylmercury, after which the now toxic bacteria are ingested by small animals, which themselves are eaten by larger and larger animals until we reach the pinnacle of the food chain, the big fish. These large fish are recognized as the natural pinnacle of the food chain, but, of course, in the same way that humans provide the mercury that works up the food chain, humans have also replaced the big fish as the apex predators. In other words, we are the ultimate beneficiaries of the deadly system we created.

The largest fish — tuna, swordfish, marlins, some sharks — are the top of the food chain, the apex predators. Yellowfin and bigeye tuna are the red-meat tunas that are popularly served in restaurants as grilled tuna steaks, tuna carpaccio, tuna teriyaki and, of course, tuna sushi and sashimi. As top predators (yellowfin and big eye tunas can be six feet long and weigh 400 pounds), these fish have a significant mercury content. The bluefin, the largest tuna of all, will naturally have the most mercury, but because the primary destination for bluefins caught around the world is Japan, Americans don’t give much thought to the mercury content of maguro. For the Japanese market, the bluefin is being so heavily fished in the Mediterranean (a bluefin spawning area) that the World Wildlife Fund has called for a complete shutdown of the tuna fisheries to save the remaining tuna from extinction.

There are fish that are safe to eat. The Monterey Bay Aquarium’s Seafood Watch lists every seafood item regularly consumed in America, and tells you whether it’s safe to eat, ecologically or toxicologically. Among the “Best Choices” are Alaska halibut, anchovies, Arctic char (farmed), bluefish, Pacific cod (the Atlantic cod has been fished to near-extinction), sole, herring, mackerel, Atlantic dorado (mahi-mahi), wild salmon and sardines. In other words, there are plenty of other fish in the sea (and in restaurants); you shouldn’t be eating tuna for health reasons — the tuna’s or yours.

Late in 2008, Island Press published Jane Hightower’s “Diagnosis Mercury: Money, Politics & Poison.” Hightower is a San Francisco doctor whose patients included a woman who complained that “her house seemed to be making her sick;” her symptoms included fatigue, headache, trouble concentrating and hair loss. She felt as if she had a hangover; sometimes she couldn’t get out of bed for a couple of days. To Dr. Hightower’s questions about her diet, the woman said she was a vegetarian and didn’t eat meat, but she ate fish — tuna, swordfish, sushi, sea bass, halibut — at least nine times a week. Testing her, Hightower found that her blood mercury level was 26.0 mcg/l (micrograms per liter), 26 times higher than the EPA guidelines.

A couple brought their 7-year-old son to see Hightower because the boy was experiencing stomachaches, headaches and lethargy, and he turned red when he was in a warm bath. The parents told Hightower that they believed that fish was good for you, so they had been feeding their son canned albacore and yellowfin tuna steadily since he was two. The boy was tested, and found to have a mercury level of about 15mcg/l. When the boy was taken off this dangerous, all-fish diet, his health improved. But, says Hightower, “He will most likely need special education and help for the rest of his life, as he still has difficulty with schoolwork, language skills and social skills.”

Even now, the only warnings given to potential consumers of tuna can be found on the EPA Web site, where pregnant women and nursing mothers are told not to eat tuna because their babies, born and unborn, are susceptible to mercury poisoning. On its “Seafood Watch” handout, based on factors that include species endangerment and human endangerment, the Monterey Bay Aquarium says that one should avoid bluefin tuna. In her book, Dr. Hightower reports that albacore tuna has three times the mercury content of “light meat” tuna, which is skipjack, a small tuna canned by the billions and found on supermarket shelves around the world. “White meat tuna” sounds somehow better than ordinary “light meat tuna,” but in fact, it contains more mercury. From the EPA Web site:

“Outbreaks of methylmercury poisoning have made it clear that adults, children, and developing fetuses are at risk from dietary exposure to methylmercury. During these poisoning outbreaks, some mothers with no symptoms of nervous system damage gave birth to infants with severe disabilities and it became clear that the developing nervous system of the fetus may be more vulnerable to methylmercury than is the adult nervous system. Mothers who are exposed to methylmercury and breast-feed their babies may also expose their infant children through their milk.”

book cover

Diagnosis: Mercury: Money, Politics & Poison

By Jane M. Hightower

Island Press, 326 pages

Buy the book

There are no warnings on cans of tuna, and hardly any in restaurants. Of course, the absence of certain fish species on restaurant menus would serve as an implicit warning, but how is the customer to know that? Because of overfishing, Caroline Bennett of London’s Moshi Moshi restaurant chain serves no bluefin in her conveyor-belt sushi bars — and says so.

Thanks to the marine conservation group Oceana, warnings are beginning to appear in supermarkets. Oceana “campaigns to protect and restore the world’s oceans by winning specific and concrete policy changes to reduce pollution and to prevent the irreversible collapse of fish populations, marine mammals and other sea life.” Its current projects include halting the slaughter of sea turtles, stopping offshore drilling, banning Mediterranean drift-netting, protecting sharks from finning, saving bluefin tuna, and encouraging supermarkets to post signs warning of the dangers of mercury in fish.

According to Oceana’s Jacqueline Savitz, “We now have convinced 36% of major grocery stores in the U.S. to post signs.” Among the chains now posting signs that contain the FDA warnings are Trader Joe’s, Whole Foods, Kroger, Harris Teeter, Costco, Albertson’s (SuperValu owned) and Safeway, and they are working on Wal-Mart, the world’s largest publicly owned corporation. A typical sign, posted adjacent to the canned fish display shelves, reads:


Pregnant and nursing women, women who may become

pregnant and young children should not eat the following fish:


They should also limit their consumption of other fish including


Notice that there is no mention of mercury, the reason for the warning in the first place. Is this because the supermarkets don’t want to frighten their customers? Because the fishing industry doesn’t want any of their products to be associated with mercury?

Because everyone knows that mercury is poison, one would assume that there would be some sort of guideline posted somewhere about what a “safe” level might be — assuming there was a safe level. But as Dr. Hightower learned, the “guidelines” are often vague, inconclusive and largely unavailable to the fish-consuming public. When Hightower questioned a research scientist at the California Department of Public Health, she was told that “a blood mercury level of 200 mcg/l was OK in adults.” That was four to 10 times what she had been seeing in her patients, and 40 times the ceiling recommended by the EPA.

When Dr. Hightower looked up mercury poisoning in a medical textbook, she learned that the symptoms included insomnia, nervousness, mild tremor, impaired judgment and coordination, decreased mental efficiency, emotional liability, headache, fatigue, loss of sex drive and depression, as well as severe paresthesias (prickling or tingling sensation of the skin), trouble speaking, trouble walking, tunnel vision, hearing loss, blindness, microcephaly (small brain size at birth), spasticity, paralysis and coma. In the “Cecil Textbook of Medicine,” she found that the “reference range” — what is considered the maximum acceptable to maintain good health — was less than 50 mcg/l for whole blood. No further information as to diagnosis, treatment, prognosis and so forth was included in the textbook.

“Diagnosis Mercury” is not only about Dr. Hightower’s patients. It is about mercury poisoning in general. In the late 1950s, in Minamata, Japan, 1,700 people died and thousands more showed aggravated symptoms of mercury poisoning after eating fish from the bay where the Chisso chemical plant was spewing mercury effluent into the water. Originally published in Japanese in 1977, Akio Mishima’s “Bitter Sea: The Human Cost of Minamata Disease,” was reissued in English in 1992. In the introduction, we read:

“As a result of the bay’s pollution with toxic organic mercury, many people were stricken with a terrible syndrome in the 1950s. Minamata disease, as it came to be known, is characterized by numbness of the extremities and the area around the mouth, constriction of the field of vision, loss of hearing, motor and speech disorders, loss of muscle coordination, convulsions, and sometimes mental aberrations, People congenitally afflicted with the disease are often mentally retarded.”

“Bitter Sea” incorporates photographs of the plant, the victims and the protesters, which serve as a painful testimony to the horrors of mercury poisoning. In 1972, more than a decade after the poisoning of Minamata Bay had been recognized, American photographer W. Eugene Smith (1918-1978) went to Japan to document the gruesome story of Minamata Bay. Although he succeeded — his photographs are heartbreaking — goons from the Chisso Chemical Co. beat him so severely that he was partially blinded and never fully recovered his sight.

Between 1962 and 1970, two communities in northwest Ontario, Canada, were warned that fish caught in the English-Wabigoon river system had record-high levels of mercury from a chemical plant up the river. By the mid-1980s, local Indian tribes received a compensation package of almost $17 million from the Dryden Chemical Co. and the provincial and federal governments. They are still advised not to eat fish from the river. Almost everybody agrees that mercury is bad for your health.

After reading “Diagnosis Mercury,” I have concluded that there really is no “safe” level of mercury, and I’m going to stop eating tuna. Why would anyone want to continue ingesting such a deadly substance? Let me repeat the symptoms of mercury poisoning: insomnia, nervousness, mild tremor, impaired judgment and coordination, decreased mental efficiency, emotional liability, headache, fatigue, loss of sex drive, and depression … severe paresthesias, trouble speaking, trouble walking, tunnel vision, hearing loss, blindness, microcephaly, spasticity, paralysis and coma.

I’m going to tell my children to stop eating tuna, and anybody else who will listen. It’s not likely that the Japanese, who buy and consume thousands of tons of bluefin tuna annually, will be scared off by mercury warnings, but it is fantastic (as in “fantasy”) to think that if enough people stop eating tuna, the fishermen would not be able to sell their catch, they would stop fishing, and the endangered bluefin would be saved from extinction. Maybe this is just a mercury-induced hallucination (until very recently, I’d eaten as much tuna as anyone), but I hereby endorse the publication and frightening conclusions of “Diagnosis Mercury.” I am tempted to quote the entire book, but the best I can do is recommend that you read it.

Richard Ellis is a celebrated marine artist and the author of more than a dozen books. He was written and illustrated articles for numerous magazines, including Audubon, National Geographic, Discover, Smithsonian and Scientific American. His newest book, on the plight of the polar bear, will be published by Alfred A. Knopf in 2009.

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