Mercury is poison. And yet it is on dinner
plates everywhere: in sea bass served in fancy restaurants,
in tuna casserole ladled out at home.
Most of the time, there is so little, it goes unnoticed.
But that doesn't mean the mercury in swordfish or shark,
trout or snapper is harmless. Eat enough -or eat enough
fish from especially polluted waters- and it can make
Too much mercury damages the nervous system, especially
the brain. Too much in pregnant and breast-feeding women
or those who may become pregnant, can hurt their babies,
adversely affecting children's intelligence, coordination,
and memory. Children under 7 are vulnerable, too, because
their young brains are still forming.
But how much is too much? And are adults at risk,
as well? Rising public concern about those questions,
which have been in the background for years, is now
prompting public health officials to look more seriously
at mercury and at its effects.
After a four-year moratorium, the U.S. Food and Drug
Administration is set to decide later this month whether
to resume measuring mercury in fish. The Environmental
Protection Agency will host a conference beginning Oct.
20 in Burlington, Vt., to discuss cases in which people
are believed to have been sickened by mercury in fish.
State and federal officials disagree over what constitutes
a safe exposure level; their programs for monitoring
mercury in fish are an on-again, off-again hodgepodge
full of scientific holes. There are no long-term studies
on Americans, and some of the studies that have been
done are contradictory or involve people whose diets
are far different from what Americans eat.
There are those who say mercury in seafood is a menace,
perhaps the biggest threat to childhood development
since scientists discovered that lead exposure lowers
IQ. They say that emissions from oil- and coal-powered
plants are spreading this poison to an alarming degree.
There are others who say the threat is overblown, that
fish, loaded with protein and heart-healthy Omega 3
fatty acids, is so good for you it outweighs any concern.
The fact is, no one knows.
"We're all looking for the truth. I don't think anybody
knows what the truth is," said Dr. Spencer Garrett of
the National Marine Fisheries Service.
Suzie Piallat has a name for it: "fish fog." Piallat,
of Tiburon, Calif., was tired and achy and she couldn't
concentrate. Finally, she went to Dr. Jane Hightower,
a San Francisco internist.
When Hightower asked Piallat if she ate a lot of fish,
she said yes: eight meals a week. And when Hightower
tested her blood, she found mercury levels of 76 parts
per billion, 15 times the amount considered safe by
the federal Centers for Disease Control and Prevention.
"I'm a health nut, I've always done the healthy thing.
I never heard any of the warnings," Piallat said. "I
thought eating fish was good for me."
Piallat, who cut back on her fish consumption, and
soon felt better, can't be faulted for missing those
warnings. It is only recently that some doctors have
reported that adult patients are being harmed by mercury
"I see people in my practice, sick from eating way
too much commercial seafood, on a regular basis," said
Hightower. Her peer-reviewed study of seafood consumption
and high mercury levels in her patients, many of whom
report symptoms such as aching joints and exhaustion,
is slated for publication by the National Institutes
of Health this fall.
There is no doubt that these patients feel sick, and
no doubt that they have high levels of mercury in their
blood. But as of yet, no study has proven the mercury
caused their illness, though Hightower notes that many
of her patients' symptoms are consistent with mercury
There are skeptics, and there is much confusion about
safe levels and whether they vary from person to person.
"It's not an absolute, like over this level everybody
dies and below this level nobody gets sick," said Dr.
Henry Anderson, medical officer at the Wisconsin Bureau
of Public Health, who studied a family contaminated
with mercury after eating Chilean sea bass and other
fish meals three to four times a week. "It's like being
on a highway, how many miles above the limit can you
go without getting arrested? There are a lot of factors
and some chance," Anderson said.
Dr. Michael Gochfeld, a clinical professor of environmental
and community medicine at Rutgers University in New
Jersey, said he sees two or three patients a year with
elevated mercury levels from eating too much mercury-laden
fish. "Ironically, these are usually health-conscious
people who have shifted their diets away from red meat
to fish," he said. "Some people eat 10 fish meals a
The latest FDA guidelines recommend that pregnant
women and small children eat no more than two meals
of fish each week. The recommendation is based on a
study conducted in the Faroe Islands, a remote archipelago
situated in the North Atlantic between Norway and Iceland.
The Faroes researchers, from Boston University, found
that children whose mothers' diets featured whale meat
or blubber during pregnancy had lower scores on a battery
of tests designed to measure intelligence, coordination,
memory, and similar skills. Children exposed to the
most mercury in utero were especially impaired in language,
memory, and attention. But even children exposed to
relatively low levels, comparable to the upper end of
the range found in the U.S. population, had some impairment.
There are some problems with the Faroes study:
· It focuses on exposure of fetuses and embryos
to mercury, while the Food and Drug Administration uses
it to gauge safety limits for adults.
Still, it may be better than the research the Environmental
Protection Agency used until recently to set its standards:
a 1971 study of people in Iraq who mistakenly ate mercury-contaminated
grain. A one-time poisonous dose of mercury -459 people
died in that incident- is not the same as long-term
exposure to slightly elevated levels.
(The most notorious incident of mercury seafood poisoning
occurred in Japan. Beginning in the 1950s, more than
1,400 people died and thousands of others were sickened
or crippled from eating fish tainted by mercury in Minamata
· The FDA guidelines use the Faroes study to
establish the number of fish meals any one person could
safely eat. In calculating that figure, the agency did
not take into account that fish from some waters have
far more mercury in them than the average serving of
Freshwater fish sampled by states bordering the Gulf
of Mexico, for example, average 3.5 times as much mercury
as the average for commercial seafood, according to
a computer-assisted analysis by the Associated Press.
Also, the Faroes results are based on people who eat
whale, a mammal rather than a fish.
· A second study, conducted in the Seychelles
Islands in the Indian Ocean off Africa, found no ill
effects from elevated exposure to mercury in fish during
Since its publication in 1998, the University of Rochester
scientists who conducted the Seychelles study have struggled
to explain why their results are so different from those
of the Boston researchers. Maybe the Faroes results
were skewed because of PCBs in whale blubber. (The researchers
deny it.) Maybe it was because of differences in the
ways the two studies measured children's development.
It is also possible that high fish consumption in
the Seychelles, while exposing children to relatively
high levels of mercury, also improves brain development.
In other words, the nutritional value of the fish itself
could actually overwhelm any negative effect of mercury.
That would resonate with the arguments of many in
the fish industry. "Fish is good for you," said Randy
Ray of the Pacific Seafood Processors Association of
Mercer Island, Wash. "Pretty much most of the ocean
is really, really safe. You've got some local water
bodies which are an issue and some fish at the top of
the food chain that are an issue, but by and large,
chow down on the shrimp."
What is beyond dispute is this: Mercury warnings for
U.S. lakes, rivers, and coastal regions increased 115
percent from 1993 to 2001. There are almost 2,000 mercury-in-fish
warnings on various water bodies in 44 states.
Mercury is a naturally occurring element found in
the Earth's crust and sometimes exposed by volcanic
eruptions, mining, and other disturbances. More commonly,
it makes its way into the environment when oil- and
coal-fired power plants burn those fossil fuels, separating
the mercury from the carbon and spewing the mercury
into the atmosphere.
Rain washes the metal from the air onto land and into
waterways, where it settles and is eaten by microorganisms
that turn it into methylmercury. Small fish then eat
the organisms, absorb the methylmercury, and are eaten
by larger fish. The methylmercury accumulates, making
its way up the food chain in ever-increasing concentrations
until people consume it.
If there is a consensus among scientists, it is that
the most vulnerable population by far is the very young,
especially still-developing fetuses. Like lead, mercury
can wreak havoc on the rapidly multiplying cells of
a growing brain, leading later in life to decreased
intelligence, lowered coordination, and impaired hearing.
"It's the chemical that can push the child over the
edge," said Dr. Philip Landrigan, chairman of the Mount
Sinai medical school's Department of Community and Preventative
According to a National Academy of Sciences report
issued in 2000, 60,000 babies born each year might be
at risk of neurological damage because of mercury, and
that is likely to mean more kids who struggle in school
and need remedial classes or special education.
Findings like these have led British authorities to
recommend that pregnant women abstain from eating any
fish at all. In Japan, where per-capita fish consumption
far outpaces that in the United States, researchers
are just beginning to investigate the effects of chronic,
low-level mercury exposure. Studies have repeatedly
shown elevated mercury levels among the Japanese as
well as medical problems in some people. However, a
Health Ministry spokesman said the Japanese government
does not issue any consumption guidelines for specific
In the United States, the FDA held a three-day conference
in July and suggested pregnant women limit the canned
tuna they eat to two, six-ounce cans a week -if that
is the only source of fish in their diets -and to only
one can if they eat other fish. The agency zeroed in
on canned tuna because it is by far the most popular
seafood Americans eat. There is no evidence it is potentially
any worse than many other fish. Canned tuna has more
mercury than scallops or catfish, for example, but less
than fresh tuna or lobster, according to a May 2001
The FDA advises pregnant women not to eat any swordfish,
shark, king mackerel, or tilefish (also known as golden
or white snapper), the species known to contain the
highest levels of mercury.
But this is not enough for some doctors and activists,
who say that because of gaps in our knowledge about
mercury, the standards are little more than educated
guesses. They lament that the FDA stopped monitoring
mercury in fish four years ago -"so that it could look
at all the data that had accumulated," said spokesman
Mike Herndon. Herndon did say why monitoring stopped
during the evaluation.
"Without an adequate mercury monitoring program for
seafood, it is virtually impossible for pregnant women
and women of reproductive age to make informed dietary
choices," said Dr. Ted Schettler of Physicians for Social
Responsibility. U.S. Sen. Ted Kennedy, D-Mass., has
also been among those pressing for a stronger FDA effort.
The Centers for Disease Control says one in 10 women
have potentially dangerous levels of mercury in their
blood. Wendy Moro was one of them.
Moro, 40, of Burlingame, Calif., wanted to get healthy,
so she ate fish: tuna for lunch, crab salad for a snack,
Sushi for dinner. But the more fish she ate, the sicker
she felt. For years, she visited doctors, neurologists,
endocrinologists, general practitioners, even a psychologist
who assured her she wasn't crazy. Just sick.
Finally Moro visited Hightower, the San Francisco
internist who tested, among dozens of other items, the
mercury levels in Moro's blood. What she found was three
times the medically safe levels spelled out by the CDC.
"I was shocked," said Moro. "We're told to eat fish,
we're told it's great for you."
And that, to experts like Dr. Jae Hong Lee, former
senior medical policy analyst at the National Center
for Policy Research for Women and Families, is the crux
of the problem. Not enough has been done to determine
the effects of mercury or the amount of mercury in fish
- or to publicize the fact that there is reason for
"The public knows about the many health benefits of
eating fish," Lee said, "but few know about the risk
of eating too much."
(Matt Crenson contributed to this report.)