Young Sentinels of Peril

Bjoerg Petersen knits her brow and chews her lip as she tries to navigate a mind-frazzling maze. She pushes her blond bangs from her forehead, rubbing it with such vigor that she seems determined to reach deep into her brain and yank the answer out.

When she succeeds, her face lights up with a wide, gap-toothed grin. When she fails, she frowns, turning to the next page of the test.

At the age of 7, Bjoerg is a typical first-grader in all but one way: Her brain has been probed by scientists since she was 2 weeks old.

Bjoerg and about 1,700 other Faroese schoolchildren are the subjects of one of the longest and most intensive environmental experiments ever conducted on humans.

Ongoing for nearly 20 years, the tests strongly suggest that a mother’s consumption of mercury-tainted seafood -- whale in the case of the Faroe Islanders -- damages her fetus’ brain as it grows in the womb, impairing her child’s intelligence in subtle ways.

Once a year, Bjoerg has electrodes fastened to her head, measuring in milliseconds how rapidly her brain receives signals. She has been asked, countless times, to recall lists of numbers and shopping items.

She has searched the crevices of her mind in vocabulary tests, tapped computer keys to measure her reaction time, arranged and rearranged blocks in patterns, and copied drawings more times than her parents can remember. She has been surrendering samples of her hair and blood since she was born. And she will probably continue to be examined by neuropsychologists until she reaches adolescence.

The children of these remote North Atlantic islands, just below the Arctic Circle, have become sentinels for the rest of the world, warning of the dangers of mercury.

The 7-year-olds most highly exposed in the womb lag behind their schoolmates in some skills -- particularly short-term memory, vocabulary and attention spans -- by as much as a school year, comparable to a decline of five or six IQ points. A physical change also has been detected: a slight slowing of the brain’s responses to signals.

The latest evidence, the results of tests on these children at 14 years published Friday, suggests that at least some of the neurological effects are long-lasting, perhaps permanent.

The findings, although partly contradicted by another large study, have had worldwide repercussions, prompting the U.S. government since 2001 to warn women of childbearing age to limit the amounts and types of fish they eat.

Children born in the Faroe Islands, part of Denmark, are highly exposed because the Faroese eat the blubber and meat of pilot whales, which contain mercury concentrations 100 times greater than fish. Pilot whales accumulate mercury by eating fish contaminated with the metal, which builds up in the ocean from emissions from power plants and other industrial operations.

The typical American carries one-tenth the mercury found in the mothers of children tested in the Faroes. But in many regions, including California’s coast, people who frequently eat ocean fish absorb as much mercury as the islanders, sometimes more.

One San Francisco physician reported last year that excessive levels of mercury were common in upper-income women and children among her patients, particularly those who regularly ate swordfish.

“The available data indicate that mercury is present all over the globe, especially in fish, in concentrations that adversely affect human beings,” the United Nations Environment Program stated in its 2003 Global Mercury Assessment.

‘Mad Hatter’ Syndrome

Proof that mercury damages the brain dates back at least 200 years, to 19th century “mad” hatters poisoned by the chemical used to cure felt. But it wasn’t until the 1950s that the dangers to fetuses became known.

At Japan’s Minamata Bay, where a chemical factory dumped tons of mercury, thousands of children were born with mental retardation and other severe problems. Similar poisoning occurred in Iraq in the 1970s, the result of contaminated grain. Toxicologists say mercury ranks among the most dangerous and widely dispersed contaminants. It is one of a few found to harm humans at doses commonly encountered in the environment.

Mercury is a natural element in the Earth’s crust, but its levels in the environment have increased threefold since preindustrial times and, in some areas, are still rising.

Every year, coal-burning power plants and waste incinerators worldwide spew about 1,500 tons into the air, more than half in Asia, according to the U.N. report.

In the United States, power plants emit about 3% of the global total. The Bush administration in December backed reducing the annual U.S. output from 48 tons to 15 by 2018, but environmentalists are calling the proposed regulations inadequate.

In humans and animals, mercury turns into methylmercury, the most toxic form. “What makes mercury a concern is that it is ubiquitous in fish,” said John Risher, a mercury specialist at the toxic substances agency of the U.S. Centers for Disease Control and Prevention.

Fish and other seafood offer an array of health benefits for adults and children, including omega 3 fatty acids that reduce heart disease. Nevertheless, adults who eat large amounts of seafood that contains mercury can experience memory lapses and increased risk of heart attacks, according to studies of fish-eaters in Finland and Brazil.

The babies of mothers who eat a lot of seafood face the most risk, scientists say, because the developing central nervous system is mercury’s most vulnerable target.

Passing through the placenta, the metallic substance attacks brain cells, dispatching them to the wrong places and disrupting the brain’s architecture.

It seems to target the growing brainstem as well as other areas, causing “widespread effects on cerebral function” that reduce a child’s memory, language and motor skills, according to Drs. Philippe Grandjean and Pal Weihe, the scientists directing the Faroe Islands studies.

Lower test scores were detected in the Faroese children at what previously had been considered safe levels of prenatal mercury exposure -- between 1 and 10 parts per million in mothers’ hair during pregnancy. Such levels are prevalent worldwide.

In the United States, one of every six babies -- about 630,000 a year -- is born to a mother with more than the EPA’s recommended 1 part per million, according to a new EPA analysis that doubled its previous estimate.

Although the effects at that level typically are mild, Weihe and Grandjean say, a worrisome pattern has shown up in the Faroes: The more mercury a child got in the womb, the lower the test scores and the slower the brain’s responses to signals. In most cases, the effects are subtle, so parents wouldn’t notice. In essence, a highly exposed child is a bit younger mentally.

“The bottom line is that IQ is affected,” said Grandjean, a professor at both Harvard University School of Public Health and the University of Southern Denmark who is renowned for his mercury research. “Each doubling of mercury takes you back one or two months at the age of 7 years, when development is particularly rapid. There’s a definite risk that these kids are not capable of catching up.”

Land of Seafarers

Descendants of 9th century vikings, the Faroese are among the world’s best fishermen.

The islands, halfway between Norway and Iceland, rise from the Atlantic in cliffs so sheer they look as though they were sliced by a razor. All 47,000 inhabitants of the 18 islands live within three miles of the ocean, and most of what they eat lives there.

In traditional slaughters called grindabod, islanders drive pods of pilot whales toward beaches and slit their throats. The free meat and blubber are shared.

In 1985, soon after his youngest child was born, Weihe began to worry what this whale diet meant for his homeland’s children. Weihe approached Grandjean, who at the time was known for his studies of another heavy metal: lead. They recruited 1,023 pregnant women -- 80% of the Faroese women who gave birth in 1986 and 1987. “My first assumption, was that we would not find any effects, that we have adapted to our diet over hundreds of years,” said Weihe, medical director of the Faroese Hospital System.

He was wrong.

Probing a Child’s Brain

To the blind eye of science, Allan Hansen is Subject No. 2 in Cohort 2.

Like most of his classmates, Allan has hair the color of straw and eyes of crystalline blue. He lives in a village of 300, where his father is a fish farmer, a lucrative profession on the islands.

Sociologists say the islands’ homogeneous genetics, affluence and low rates of family instability and alcoholism make it ideal for studying neurotoxins because such social factors would have little influence on the children’s intelligence.

Since infancy, Allan, Bjoerg and the 180 other children of Cohort 2 -- the second of three groups assembled in the Faroes -- have undergone tests to measure specific brain functions. Allan, who performs well on the tests, listens intently to the instructions of clinical neuropsychologist Frodi Debes. The boy’s tennis shoes swing in the air, only the tips of his toes reaching the floor -- a reminder that Subject No. 2 is a mere 7-year-old.

Flashing black-and-white images, Debes asks Allan to name them in his native Faroese. He sails through the first dozen or so -- tree, house, scissors, flower, helicopter. He struggles with others, some unknown in the Faroes -- pretzel, igloo, unicorn. His score is high, indicating a vocabulary larger than most of his schoolmates’.

This is a critical test, one in which mercury seems to have its largest effect. For every doubling of prenatal exposure, there is a two-month delay in vocabulary, comparable to a 1.5-point drop in IQ. Those exposed to a tenfold increase had a seven- to eight-month delay, almost an entire school year. Next, Debes recites a shopping list of 15 foods, toys and clothing items. On the first try, Allan recalls five, slightly above average. This test is another in which mercury is linked to performance, in this case reduced memory. Other tests, using computers, drawings and blocks, judge his attention span, reaction time and fine-motor skills.

Then, a web of red, green and yellow wires is strapped onto Allan’s head. In a darkened room, he stares at a screen flashing checkerboard patterns. He then dons headphones, listening to clicks while a computer records electrical signals sent to his brain from his eyes and ears. In the studies, the ears’ messages were received at a slightly slower pace in children who had double the lowest prenatal exposure to mercury.

A little more than three hours into the testing, with two more hours to go, Allan looks exhausted. His mother, Winnie Hansen, kisses his head. “It takes a long time for such a young child,” Hansen says with a sigh.

The scrutiny began before Allan was born, when Hansen was pregnant and gave hair samples to measure the mercury she was passing to her baby.

Children like Bjoerg and Allan -- whose mothers ate low to moderate amounts of whale, a half-dozen or so meals during pregnancy -- generally get higher marks than peers exposed to more mercury.

More than 850 of the children in the original 1986 group were tested until they reached 14. Weihe had hoped that the effects would disappear with age. But initial results from the teens, published Friday in the Journal of Pediatrics, show that at least some of the damage most likely is irreversible.

As was the case when they were 7, their brains at the age of 14 responded less quickly to signals from their ears if they had been exposed to elevated levels of mercury in the womb.

Also, the teens with higher exposure had neurological changes that made them less able to maintain a normal heart rate, a condition that increases the risk of heart attacks later in life, according to Grandjean and Weihe.

“Here we have actual effects on humans,” Weihe said, “not based on factory accidents but on humans who are living their normal way, as they always have.”

School Work Suffers

Joseph Jacobson, chairman of the cognitive and social psychology department at Wayne State University in Detroit and a member of the National Research Council’s mercury committee, said the more heavily exposed children “might have deficits that are severe enough to markedly affect their day-to-day function.”

The National Research Council concluded that the effects detected in the children “are likely to be associated with increases in the number of children who have to struggle to keep up in a normal classroom or who might require remedial classes or special education.”

The societal impacts of mercury “can be tremendous,” according to a report in the journal Environmental Health Perspectives co-written by Deborah Rice, formerly with the EPA. A universal drop of five IQ points would double the number of U.S. children with IQs under 70 who require remedial help at school, the report said.

Scientists are now investigating whether mercury in seafood, and a type of mercury called thimerosal formerly used in childhood vaccines, might also contribute to autism and other neurological disorders.

So far there is no “convincing evidence,” said Dr. David Bellinger, a Harvard Medical School neurologist who also served on the national mercury committee. But several large studies, including one in California, are “just getting underway, so I think we’ll have better answers to this question in the next few years,” he said.

Some medical experts, citing a study conducted in the Seychelle Islands in the Indian Ocean, question whether the Faroe Islands findings are applicable worldwide.

A study of nearly 800 children in the Seychelles found no link between mercury exposure and neurological performance. Seychelles mothers eat 12 meals of ocean fish a week -- so much that their mercury levels are similar to those in the Faroese women.

Dr. Gary Myers of the University of Rochester, lead scientist for the study, wrote that the results “do not support the hypothesis that there is a neurodevelopment risk ... resulting solely from ocean fish consumption.”

Nevertheless, the EPA relied on the Faroes results in setting advisories on how much fish is safe to eat, and the National Research Council agreed.

The Faroese studies have been under “extensive scrutiny” and “the weight of evidence of developmental neurotoxic effects ... is strong,” the National Research Council panel’s 2000 report said. Also, tests on children in New Zealand and Brazil detected similar effects linked to fish consumption.

Scientists say the contradictory results could reflect discrepancies in how the tests were conducted or social disparities between the island cultures. Bellinger said nutrients and minerals, such as selenium, might reduce susceptibility to mercury.

Children as Messengers

A few years after Allan and Bjoerg were born, the Faroese government began advising women of childbearing age to stop eating whale.

“The pilot whale has been the backbone of our culture and very important for our people’s diet throughout the centuries,” Prime Minister Anfinn Kallsberg said in an interview. But, he added, he was “quite convinced” of the neurological results.

Faroese women have mostly heeded the instructions. Today, they contain one-tenth as much mercury as in 1986, when the children in the first study were born. They are now on par with people in the rest of Europe and the United States.

Yet elevated exposures persist worldwide, particularly in Greenland, where the Inuit eat marine mammals, and in Amazonian and African villages near mercury-tainted gold mines.

Even in the United States, there are extremes in exposure, depending on how much and what kind of fish are eaten.

One San Francisco-area woman who ate commercially sold swordfish 14 times a month suffered memory lapses and her hair began to fall out. A toddler regularly fed salmon and sole had mercury levels more than twice the recommended amount, said their physician, Jane Hightower.

Though the youngsters of Kallsberg’s homeland are in a unique position to chronicle mercury’s hazards, he stresses that they are merely messengers of a global threat to children.

“We are victims of the pollution that other nations create,” the prime minister said. “Once it’s released, it’s not anymore their problem. It becomes ours.”

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A Guide for Landing Safe Seafood

Because of seafood’s many nutritional benefits, medical experts say the best protection for women of childbearing age is to avoid fish with high contaminant levels, not to avoid all fish.

The highest mercury concentrations are in large predatory species, particularly swordfish, king mackerel, shark, tilefish and opah. Medium to high levels are found in fresh and canned albacore tuna, grouper, red snapper and orange roughy. Among the safest fish in terms of mercury are salmon, shrimp, crab, light canned tuna, sea bass, herring, catfish and tilapia.

The U.S. Food and Drug Administration advises women of childbearing age and children to stop eating swordfish, king mackerel, shark and tilefish. But it says that eating up to 12 ounces a week of a variety of other fish is safe. A 6-ounce serving is equivalent to a can of tuna.

But some health officials and environmental groups say the advisory does not sufficiently protect babies and children, so they want it extended to other fish with medium to high mercury levels.

Using an FDA formula, the Environmental Working Group said women should eat no more than 6 ounces per week of 13 other fish: fresh tuna, canned albacore tuna, grouper, red snapper, lobster, marlin, opah, orange roughy, saltwater bass, freshwater and seawater trout, bluefish and croaker.