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The warning
against eating mercury-contaminated fish announced in March by the
Food and Drug Administration (FDA) and the U.S. Environmental Protection
Agency (EPA) is proof that we need to remove mercury from commerce,
according to a top scientist at the Natural Resources Defense Council
(NRDC).
Linda Greer, an environmental toxicologist at NRDC, also said the
health advisory does not adequately warn parents about feeding their
children albacore tuna, given the EPA’s own data.
“This advisory does not do enough to help parents ensure that
their children are not exposed to harmful amounts of mercury,”
said Dr. Greer. “But that obscures the larger issue. Just as
we did with lead, we have to take mercury out of commerce.”
The advisory does not warn consumers about eating some of the most
highly-contaminated fish, she said. For example, it does not mention
grouper and orange roughy, two popular fish dinner entrées
that, according to recent FDA test data, have high mercury levels.
It also does not provide specific advice for parents with young
children. The advisory states that children should eat less than
12 ounces of fish a week, but does not specify how much less. Based
on FDA data, a 22-pound toddler who eats three ounces (one-half
of a six-ounce can) of albacore tuna a week would ingest nearly
four times the EPA’s safe level, and an 88-pound child eating
six ounces would be exposed to twice EPA’s safe level.
Like lead, mercury damages the brain and nervous system. Mercury
exposure can lead to developmental problems, learning disabilities
and mental retardation. Infants and children are at most risk, according
to the Centers for Disease Control and Prevention and the EPA. One
in 12 American women of childbearing age have mercury in their blood
above the level that could pose a risk to a developing fetus.
The NRDC reports that mercury pollution has contaminated 12 million
acres of lakes, estuaries and wetlands—30 percent of the national
total—and 473,000 miles of streams, rivers and coastlines.
Last year, 44 states issued warnings about eating mercury-contaminated
fish, a 63 percent jump from 1993, when 27 states issued such warnings.
Nineteen states have issued statewide advisories for mercury in
freshwater lakes and rivers, and 10 states have issued advisories
for canned tuna.
In NRDC’s Mercury Contamination in Fish: A Guide to Staying
Healthy and Fighting Back, a wide range of information on mercury’s
effects and its sources, as well as tips for eating fish more safely,
are examined. (See www.nrdc.org/health/effects/mercury/index.asp.)
A brief review of guide highlights follows.
Examining the Exposure
Over the years, many companies have used mercury to manufacture
a range of products including thermometers and thermostats, automotive
light switches and “silver” dental fillings. Although
the metallic mercury in these products rarely poses a direct health
hazard, industrial mercury pollution becomes a serious threat when
it is released into the air, primarily by power plants and certain
chemical facilities, and then settles into oceans and waterways,
where it builds up in fish that we eat.
Once mercury enters a waterway, naturally occurring bacteria absorb
it and convert it to a form called methyl mercury. This transition
is particularly significant for humans, who absorb methyl mercury
easily and are especially vulnerable to its effects.
Mercury then works its way up the food chain as large fish consume
contaminated smaller fish. Instead of dissolving or breaking down,
mercury accumulates at ever-increasing levels. Predatory fish such
as large tuna, swordfish, shark and mackerel can have mercury concentrations
in their bodies that are 10,000 times higher than those of their
surrounding habitat.
Humans risk ingesting dangerous levels of mercury when they eat
contaminated fish. Since the poison is odorless, invisible and accumulates
in the meat of the fish, it is not easy to detect and can’t
be avoided by trimming off the skin or other parts. Once in the
human body, mercury acts as a neurotoxin, interfering with the brain
and nervous system.
Exposure to mercury can be particularly hazardous for pregnant women
and small children. During the first several years of life, a child’s
brain is still developing and rapidly absorbing nutrients. Prenatal
and infant mercury exposure can cause mental retardation, cerebral
palsy, deafness and blindness. Even in low doses, mercury may affect
a child’s development, delaying walking and talking, shortening
attention span and causing learning disabilities.
In adults, mercury poisoning can adversely affect fertility and
blood pressure regulation and can cause memory loss, tremors, vision
loss and numbness of the fingers and toes. A growing body of evidence
suggests that exposure to mercury may also lead to heart disease.
Mercury in the Food We Eat
The most common source of mercury exposure for Americans is tuna
fish. Tuna does not contain the highest concentration of mercury
of any fish, but since Americans eat much more tuna than they do
other mercury-laden fish, such as swordfish or shark, it poses a
greater health threat. Subsistence and sports fishermen who eat
their catch can be at a particularly high risk of mercury poisoning
if they fish regularly in contaminated waters.
The following recommendations about eating fish issued by the NRDC
are largely designed for the people most at risk from mercury poisoning:
children and women of childbearing age. Other adults may not need
to restrict their diets as much, but can use these guidelines to
make informed choices.
* Avoid contaminated fish: Children under six, as well as women
who are pregnant or planning to become pregnant, are the most vulnerable
to mercury’s harmful effects. They should restrict or eliminate
certain fish from their diet, including tuna, tilefish, swordfish,
shark, king mackerel, grouper and fish caught in any waters that
are subject to a mercury advisory. Women with elevated mercury levels
should begin avoiding or restricting their consumption of mercury-laden
fish as much as a year before they become pregnant.
* Restrict your portions: In general, a woman who is pregnant
or is likely to get pregnant should eat no more than two cans of
light tuna per week, or two-thirds of a can per week of white albacore
tuna if she wants to be sure to stay below the EPA’s level
of concern for mercury. Keep in mind that the amount of mercury
in a single can varies depending on where the tuna was caught. Albacore
or solid white tuna is most likely to have higher concentrations,
and chunk light tuna, lower concentrations.
Raw tuna and other sushi fish are also something to watch out for.
Often the apex predators of the food chain, these fish tend to be
high in mercury.
Since children get most of their mercury from canned tuna, it is
important for parents to limit their children’s consumption
to less than one ounce of canned light tuna for every 12 pounds
of body weight per week, in order to stay below the level of mercury
the EPA considers safe. That means that a child who weighs 36 pounds
should not eat more than three ounces (half a standard-sized can
of chunk light tuna) per week. Children should avoid albacore or
white tuna because the levels of mercury are higher.
* Check your mercury level: For an accurate reading, you can
request a blood mercury test from your physician. Women with a high
blood mercury level who are planning to start a family may decide
to postpone pregnancy for a few months until levels drop; often
this occurs over a three- to six-month time frame.
* Be an activist: The NRDC is tracking proposals by the EPA
and the FDA to protect the public from mercury poisoning. To receive
regular updates and participate in decision-making on these and
other environmental and health issues, join NRDC’s Earth Activist
Network or send a message to the EPA to get poisonous mercury out
of our fish (see www.nrdcaction.org).
Lastly, urge your grocery stores, fish markets and restaurants to
label fish accurately and advise consumers about the dangers of
mercury in the fish they sell.
| NRDC'S CONSUMER GUIDE TO MERCURY IN FISH |
The list below shows the amount of various types
of fish that a woman who is pregnant or planning to become pregnant
can safely eat, according to the EPA. People with small children
who want to use the list as a guide should reduce portion sizes.
Adult men, and women who are not planning to become pregnant,
are less at risk from mercury exposure, but may wish to refer
to the list for low-mercury choices.
Certain fish, even some that are low in mercury, make poor choices
for other reasons, most often because they have been fished
so extensively that their numbers are perilously low or if the
methods used to catch them are especially damaging to other
sea life or ocean habitats. These fish are marked with an asterisk.
This list applies to fish caught and sold commercially. For
information about fish you catch yourself, check for advisories
in your state. Fish are listed in descending order, so those
at the bottom of each category are lower in mercury than those
at the top. |
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HIGHEST MERCURY
(more than .55 parts
per million) |
HIGH MERCURY
(from 0.26 to 0.55 parts per million) |
LOWER MERCURY
(from 0.12 to 0.25 parts per million) |
LOWEST MERCURY
(less than 0.12 parts
per million) |
Avoid
Tilefish *
Swordfish
Shark *
Mackerel (king) |
No more than two 6-ounce servings per month
Grouper *
No more than one 6-ounce serving per week
Orange roughy *
Marlin *
Tuna (canned,
white albacore)
Sea trout
Tuna (fresh) *
Bluefish
Lobster |
About two 6-ounce servings per week
Halibut
Rockfish *
Mahi Mahi
Crab (dungeness)
Haddock *
Snapper *
Crab (blue)
Herring
Crab (snow)
Cod *
Tuna (canned,
chunk light)
Sea Bass *
Trout (freshwater) |
No limit
Perch (freshwater)
Crab (king)
Pollock *
Catfish
Whitefish
Perch (ocean) *
Croaker
Scallops *
Flounder *
Sole *
Trout (farm raised)
Crawfish/crayfish
Salmon
Shrimp *
Clams
Tilapia
Oysters
Sardines |
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