By Ken Cook, President
of the Environmental Working
Fish is beyond compare as a source of
many nutrients vital to the developing infant, some of which
may actually enhance development of the nervous system in
babies and young children.
contamination of fish with toxic mercury, however, has cast
a shadow over the nutritional benefits of fish.
Exposure to mercury in the womb can
cause learning deficits, delay the mental development of
children, and cause other neurological problems. Mercury
consumed by a pregnant woman through contaminated fish can
cross her placenta to damage the brain of her baby.
As a National Academy of Sciences panel
definitively warned last year, some children exposed in
utero by their mothers' fish consumption are at risk of
falling in the group of children "who have to struggle
to keep up in school and who might require remedial classes
of special education."
Combustion in power plants of coal containing
mercury is the major source of environmental
Tons of Mercury are released into the US EVERY year by this
Mercury pollution from coal-fired power
plants moves through the air, is deposited in water and
finds its way into fish, accumulating especially in fish
that are higher up the food chain. Fish like tuna, sea bass,
marlin and halibut show some of the worst contamination,
but dozens of species and thousands of water bodies have
been seriously polluted.
As a result,
women who eat a lot of fish during pregnancy, or even as
little as a single serving of a highly contaminated fish,
can expose their developing child to excessive levels of
mercury. The toxic metal can cross the placenta to harm
the rapidly developing nervous system, including the brain.
In this report, EWG researchers for
the first time attempt to characterize just how common such
exposures are in the U.S. population, and the associated
One key to the analysis is a much more
refined representation of differences among women - their
size, metabolism of mercury, blood volume, and many other
biological variables. Government assessments use "averages"
or constants for all of these factors, missing profound
differences across the population of women of child bearing
analysts also assembled the most extensive database ever
developed on mercury levels in various species of fish,
drawing on federal, state and other government sources,
some 56,000 records in
That exercise revealed major variations
in mercury contamination across fish species, yielding vital,
highly practical information women can use while pregnant
to reduce mercury exposure dramatically, while still enjoying
the nutritional benefits of fish.
Earlier this year, the Food and Drug
Administration came up with its own list of fish that pregnant
and nursing women, along with infants, should avoid. Based
on our analysis of much more extensive fish contamination
records, the list presented in this report is more complete.
By analyzing these two data sources
in combination, the study is able to provide new insights
into how women can avoid excessive mercury exposures during
Researchers at US PIRG
Education Fund, co-authors of this study, made another vital
contribution. PIRG painstakingly combed through hundreds
of "fish advisories" issued by state agencies
to warn people about mercury levels in sport and game fish
in literally thousands of US lakes and rivers.
What they found is disturbing: while
some states are doing a better job than others, virtually
no fish advisories for mercury contamination are adequately
protective of human health when judged against current scientific
The importance of this new understanding
about mercury risks was evidenced in a landmark study on
blood levels of mercury and other toxins, released by the
federal Centers for Disease Control and Prevention (CDC)
in March, 2001.
While "average" blood mercury
levels among women were not of concern, the data indicate
that in fully 10 percent
of American women -- roughly 7 million women -- mercury
levels were above the dose that may put a fetus at risk
for adverse nervous system effects.
Those women surely don't need more mercury
in their system, least of all if they are already pregnant
or nursing. As this report recommends, the government must
start monitoring such exposures, and any possible effects,
much more energetically. This is a simple, common sense
matter of public health.
In the longer term, the solution is
to halt mercury pollution from coal-burning power plants
and other sources so the contamination of fish is avoided
in the first place. Fuel switching -- from coal to renewable
energy sources -- along with aggressive deployment of conservation
measures, makes sense for any number of reasons.
Fish free of mercury -- the way they
used to be -- is just another one.
On January 12, 2001, government health
officials issued new advisories warning women to limit fish
consumption during pregnancy to avoid exposing their unborn
children to unsafe levels of methylmercury.
Methylmercury can cross the placenta
and cause learning deficits and developmental delays in
children who are exposed even to relatively low levels in
the womb. The principal exposure route for the fetus is
fish consumption by the mother.
The Food and Drug Administration (FDA),
which regulates commercially sold fish, recommends that
pregnant and nursing women
and young children not eat any shark, swordfish, tilefish,
or king mackerel, but then recommends 12 ounces per week
of any other fish.
The Environmental Protection Agency
(EPA), which makes recommendations to states about safe
mercury levels in sport fish, allows up to 8 ounces of any
fish per week for pregnant women with no prohibitions on
consumption of any individual fish caught recreationally.
are steps in the right direction, but they need to be tightened
significantly to adequately protect women and their unborn
children from the toxic effects of methylmercury.
The nutritional benefits of fish complicate
the task faced by health officials when protecting the public
from methylmercury. Protein, omega-3 fatty acids, Vitamin
D, and other nutrients make fish an exceptionally good food
for pregnant mothers and their developing babies.
At the same time, there is no doubt
that methylmercury is toxic to the fetal brain and nervous
system, and that many beneficial fish species are contaminated.
EPA's safe exposure estimate for methylmercury has dropped
twice in the past 16 years, as new science has identified
adverse effects in children exposed in the womb at lower
and lower doses.
Emerging evidence indicates that the
safe dose may drop even lower in the future (NAS 2000).
Just how long a fetus can tolerate a dose of methylmercury
above a "safe level' with no observable adverse effects
is a matter of ongoing debate.
Compounding this uncertainty is the
lack of effective education and outreach to pregnant women
about methylmercury risks and the near total absence of
information for pregnant women on the levels of mercury
in the fish they buy. New data from the Centers for Disease
Control and Prevention (CDC) show that about 10 percent
of all women of childbearing age have blood methylmercury
levels above the dose that may put their fetus at risk for
adverse neurological effects (CDC 2001).
If these women were to increase their
consumption of certain fish species in hopes of benefiting
their babies during pregnancy, they could expose their fetuses
to potentially hazardous levels of methylmercury.
FDA's methylmercury safeguards are designed
to protect an average-sized woman eating an average fish
contaminated with an average amount of methylmercury that
decays in her body at an average rate. These assumptions
rarely apply to the risks faced by any individual.
Instead, risks are unevenly distributed
throughout the population, with a small but significant
number of pregnancies exposed to far higher and potentially
unsafe levels of methylmercury than the average fetus. The
10 percent most-heavily exposed American women already have
blood methylmercury levels that would increase health risks
to their fetuses if they became pregnant (CDC 2001). FDA's
health advisory, based on average exposures, does little
to protect these children.
Working Group assessed fetal exposure to methylmercury
taking into account a host of real world differences in
individual exposure, including a mother's body weight and
blood volume, varying methylmercury absorption and distribution
rates, and variable rates of methylmercury decay in different
pregnant women (Stern 1997, CDC 2001, NAS 2000).
These biological differences were matched
up with a unique database of fish contamination that contains
56,000 records of methylmercury test results from seven
different government sources. Fish consumption, fish contamination
levels, and biological variables were matched thousands
of times to create a distribution of blood methylmercury
levels in women similar to that occurring in the general
This distribution was compared to the
benchmark dose of methylmercury recommended by the Committee
on the Toxicological Effects of Methylmercury of the National
Academy of Sciences (NAS 2000).
FDA's recommendation of 76 6-ounce fish meals during pregnancy
could actually be detrimental to the health of unborn children.
Fish are an important part of a healthy diet and women should
be encouraged to eat fish with low methylmercury levels
if American women ate a varied diet of FDA's recommended
12 ounces of fish a week (and none of the four prohibited
fish) they would expose more than one-fourth of all babies
born each year (1 million infants) to a potentially harmful
dose of methylmercury for at least one month during pregnancy.
20,000 of these children would be exposed to a dose of methylmercury
that increases the risk of adverse neurological effects
for the entire pregnancy.
and state fish advisories for sport fish
EPA provides guidance on safe methylmercury
exposure levels to state officials who in turn issue consumption
advisories for sport fish caught by recreational anglers.
State authorities typically post fish advisories for individual
water bodies where fish are contaminated with methylmercury
at a level that they deem unsafe for women of childbearing
Some states have done a better job than
others in protecting their populations from methylmercury,
but an analysis by US PIRG
and the State PIRGs shows that only Massachusetts has adopted
health safeguards that protect all women and children.
The broader issue with recreational
fish, however, is whether these advisories translate into
conscious choices by pregnant mothers to avoid eating contaminated
fish. There is a substantial body of evidence indicating
that they do not (Golden et al 2001).
Fish provide important health benefits
to the developing fetus, and pregnant women should be encouraged
to eat fish with consistently low methylmercury levels.
With too many species, however, these nutritional pluses
are outweighed by the hazards of methylmercury.
Federal health authorities need to take
much stronger steps to protect a far greater portion of
the population. They must move beyond their antiquated safeguards
designed to protect an average woman from an average amount
of methylmercury in fish and take a realistic and protective
stance against dietary exposure to methylmercury.
There are three ways that the FDA methylmercury
health advisory must be improved:
The list of fish to avoid
during pregnancy must be expanded.
By advising against the consumption
of just four types of fish, FDA allows heavy consumption
of many fish that have unacceptably high methylmercury levels.
To protect women and their babies from methylmercury, the
FDA must add the following species to the list of seafood
that should not be eaten by pregnant women, nursing women,
and women considering pregnancy:
Oysters (Gulf of Mexico)
While not every serving of any of these
fish is contaminated with dangerous levels of methylmercury,
the odds are greater than one in 1,000 that consumption
of a single meal of these fish will expose the fetus to
a potentially hazardous amount of methylmercury for longer
than 30 days.
recommendation that pregnant women eat 12 ounces a week
of any fish (except the four that are not allowed) must
be radically revised.
Ten percent of American women enter
pregnancy with elevated methylmercury levels, and current
FDA safeguards, which are based on average exposures, do
almost nothing to protect these high exposure pregnancies.
If these women follow FDA's advice of 12 ounces of any fish
a week, they could easily expose their fetuses to a level
of methylmercury that presents a real risk of adverse neurological
effects. To protect women and children, FDA must restrict
consumption of the following fish to no
more than one meal per month, for all species combined:
Salmon from the Great Lakes
Blue crab from the Gulf of Mexico
Channel catfish (wild)
Women who want to eat fish during pregnancy must have information
about which species are least
contaminated with methylmercury. Pregnant women
have a right to this information, and FDA has a duty to
provide it. In addition to strengthening restrictions on
fish consumption by pregnant women, FDA should promote the
following fish as safe options for pregnant women:
Shrimp * (see sidebar)
Salmon (wild Pacific)
Blue crab (mid Atlantic)
It was not possible for EWG to assess
the methylmercury risk from every recreational fish caught
in every lake in every state in the country. A review of
the available data, however, shows that several large predator
sport fish are so universally contaminated that FDA should
add them to the list of fish that women should completely
avoid during pregnancy.
After analyzing the results of more
than 10,000 samples from 792 lakes and rivers nationwide,
we recommend that FDA add the following species to their
health advisory: walleye,
northern pike, and largemouth bass. While FDA
has no authority to regulate methylmercury levels in freshwater
fish, they do have a responsibility to provide critical
health information to the public. It is important that women
receive a consistent message from one source, and the FDA
is the appropriate agency to deliver this message.
monitoring of fish for methylmercury contamination
A major flaw in FDA's system is the
agency's own lack of comprehensive data on methylmercury
in fish. In January 2001, FDA recommended that pregnant
women avoid consumption of king mackerel based on methylmercury
levels from a study published in 1979. There are many other
species where the data on methylmercury contamination are
similarly outdated, but where the available information
indicates a potential problem.
FDA must immediately expand its methylmercury
sampling program to include a host of fish where the data
indicate that pregnant women and their babies could receive
a potentially unsafe exposure from a relatively small amount
public access to mercury contamination data
Consumers have a right to know about
contamination of the food supply, and FDA must be responsive
to this right. Currently they are not. EWG had great difficulty
obtaining relatively simple information about fish contamination
from the agency through the Freedom of Information Act.
FDA currently posts the results of its Total Diet Study
on the web, and there is no reason that all of the agency's
mercury contamination information could not be posted as
FDA needs to move beyond its antiquated
and biologically implausible risk assessment methods based
on average people and average fish and adopt state-of-the-art
risk assessment techniques that provide a much more realistic
picture of mercury exposure and risk as it is distributed
throughout the population.
It is not sufficient to protect the
population from average exposures when it is clear that
many individuals have far greater than average exposures
for extended periods of time.
Pollution at its Source
Mercury emissions from coal-fired power
plants, the largest man-made source of environmental mercury,
are currently completely unregulated. Federal decision-makers
should require power plants to reduce their mercury pollution
by 90% and ultimately move away from polluting sources of