Over recent years NOW has examined how the influence
of the tuna industry on the FDA may be putting Americans
and their children at risk for mercury poisoning. Tuna,
widely known for its health benefits, is one of the most
popular foods on grocery store shelves. And, in 2000,
FDA draft advisories presented to focus groups warned
women not to eat a lot of canned tuna during pregnancy
because it contains levels of mercury that can harm
developing fetuses and nursing babies. In March 2004,
the FDA and the EPA issued the first ever joint advisory
on this topic,
What You Need to Know About Mercury in Fish and
Shellfish.
The State of California has gone a step further. In
2003 the California Attorney General's office filed suit
to force supermarkets, restaurants and tuna companies to
warn customers that tuna (fresh, frozen and canned),
swordfish and shark sold in their markets contain
mercury. The suit was based on the state's Proposition
65 which requires consumer warnings for substances on a
toxics list. The state also provided special warnings
advising women and children to "Limit their consumption
of other fish, including tuna." And they further advised
that "tuna steaks and canned albacore have higher levels
of mercury than canned light."
In January 2005, 16 major restaurant chains sued by
the state agreed to settle and put up warnings. And a
few supermarkets have voluntarily posted them at fresh
fish counters and in the frozen food section. The US
Tuna Foundation is challenging the lawsuit saying
"canned tuna products are safe…." Citing the
above-mentioned mercury advisory by the Food And Drug
Administration and the Environmental Protection Agency
that states "fish and shellfish are an important part of
a healthy diet."
Nearly all fish contain trace amounts of methyl
mercury. How does this element get into our fish
supply? Mercury occurs both naturally and from
man-made sources. Some of it can be traced to
coal-burning power plants. Smokestacks release toxic
mercury emissions which rain down into rivers,
lakes, and oceans. Bacteria convert the mercury to a
form that's easily absorbed by insects and other
small organisms. Mercury moves up the food chain as
small fish eat the small organisms and big fish eat
the smaller fish. The highest concentrations
accumulate in large predators such as shark,
swordfish and tuna...some of America's favorite
fish.
Pregnant women, nursing mothers, and very young
children are cautioned against excessive consumption
of these fish. Read the
FDA consumer advisory for pregnant women about
the risks of mercury in fish. The FDA also offers a
chart on mercury levels in seafood species.
Until the 1950's, the problems that can occur
with excessive mercury intake were not well-known.
However, at that time, an epidemic hit fishermen and
their families in villages on Japan's Minamata Bay.
People whose diet was primarily seafood showed signs
of brain damage; some were even fatally stricken
with disease and seizures. The investigation linked
the health problems to methylmercury poisoning from
a local chemical plant that was discharging organic
mercury into the bay. The villagers were getting
sick from eating the fish that had absorbed the
mercury. (Learn more about
The Poisoning of Minamata.)
In 1969, the FDA first set an action level for
total mercury in fish; 0.5ppm (part-per-million) was
considered the maximum safe limit. (Action levels
represent the limit at or above which FDA will take
legal action to remove a product from the market.)
In 1979, the action level was raised to 1ppm. In
1984, there was another major change. The FDA
stopped measuring on a basis of total mercury and
instead started checking levels in terms of
methyl mercury only. In 1998, the FDA stopped widely
testing for mercury in fish.
Around the world, there is concern about mercury
contamination through fish, but specific
recommendations vary. For example, Health Canada
advises consumers to limit their consumption of
swordfish, shark or fresh and frozen tuna to one
meal per week; for young children and women of
child-bearing age, the recommended limit is one meal
per month. Health Canada's guideline is 0.5ppm total
mercury content — more stringent than in the U.S.
Britain's Food Standards Agency is advising pregnant
and breastfeeding women and women who intend to
become pregnant to limit their consumption of tuna
to no more than two medium-size cans or one fresh
tuna steak per week.
Even within the United States, women are hearing
different advice from different sources, especially
where tuna is concerned. The EPA's methylmercury
guideline is a recommended limit on mercury
consumption based on bodyweight, also known as a
"reference dose." EPA's methylmercury reference dose
is .1 micrograms/kg body weight per day. In July
2000, the National Academy of Sciences found the
EPA's reference dose as "scientifically justifiable"
for protecting most Americans.
So exactly how much mercury a 45 lb. child would
ingest by eating one 6 ounce can of tuna per week,
and how does that compare to the EPA's reference
dose? Take a look at the following calculations:
Step 1 - DETERMINE EPA's RECOMMENDED LEVEL
FOR A 45 LB CHILD
- Multiply child's body weight by EPA's
reference dose.
- Convert 45 pounds to kilograms = 20.45
kilograms
- 20.45 kilograms x .1 micrograms per kilogram
per day
EPA RECOMMENDED LEVEL = 2.05 micrograms per day =
14.35 micrograms per week.
Step 2 - HOW MUCH MERCURY IS IN 6 OUNCES OF
CHUNK WHITE TUNA?
- Multiply amount of fish by average mercury
level for chunk white albacore.
- Convert 6 ounces to grams = 170 grams 170
grams X .31 ppm (or micrograms per gram)**
MERCURY INGESTED = 52.7 micrograms per gram
Step 3 – COMPARE MERCURY INGESTED WITH EPA'S
RECOMMENDED LEVEL
- Divide 52.7 micrograms by 14.35 micrograms =
3.7
BY EATING 6 OUNCES OF CHUNK WHITE TUNA A WEEK,
THE CHILD IS INGESTING ALMOST FOUR TIMES EPA'S
RECOMMENDED DOSE.
In December 2003, the FDA began circulating a
draft advisory warning women who are pregnant,
nursing, or who might become pregnant about the
dangers of mercury in seafood. Critics like the
Environmental Working Group objected to the
advisory's vague guidance on tuna, and subsequently
filed a legal challenge, charging that the advisory
did not meet standards for accurate government
science established by the Data Quality Act.
In February 2004, a new analysis by the
Environmental Protection Agency revealed that "about
630,000 children are born each year at risk for
lowered intelligence and learning problems caused by
exposure to high levels of mercury in the womb,"
nearly double the previous EPA estimate.
Read more about mercury and tuna from the
Mercury Policy Project and from the
U.S. Tuna Foundation.
Also, the Sea Turtle Restoration Project
Mercury Calculator allows users to gauge mercury
exposure from seafood by entering a log of how much
fish they consume.
**Average for Chunk White Canned Tuna. Yess,
Norma J. "US Food and Drug Administration Survey of
Methyl Mercury in Canned Tuna," Journal of AOAC
International, Vol. 76, No. 1, 1993, pp. 36-38.