=======================Electronic Edition========================
RACHEL’S HAZARDOUS WASTE NEWS #291
—June 24, 1992—
News and resources for environmental justice.
——
Environmental Research Foundation
P.O. Box 5036, Annapolis, MD 21403
Fax (410) 263-8944; Internet: erf@igc.apc.org
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AN OLD PROBLEM, MERCURY POLLUTION,
REAPPEARS IN A TROUBLESOME NEW FORM
An old problem, mercury pollution of freshwater fish, re-emerged
during the late 1980s in a form much more widespread and much
more difficult to control than previously seen.
Federal and state governments have done little to attack the
problem, partly because much of the bad news is recent, and
partly because government policies created much of the problem in
the first place.
Mercury contamination first became known in the U.S. in 1970 when
big fish in the Great Lakes were discovered to be so laced with
mercury that they were poisonous to humans. The source was
thought to be industrial dumping of mercury directly into
waterways.[1] After various industries reduced their mercury
dumping into streams and lakes, pollution control officials
assumed the problem was under control and basically went to sleep.
However, throughout the 1970s, Swedish researchers continued to
report high mercury levels in fish taken from remote lakes, far
from any industrial polluters. In the early 1980s, Minnesota
officials began examining fish from remote lakes and they too
found fish with dangerously high mercury concentrations. Then
officials in Wisconsin and Michigan made similar discoveries. In
the Canadian province of Ontario, researchers found high levels
of mercury in 95% of all the lakes tested.[2]
Scientists assumed the source of the mercury was natural geologic
deposits until recently when careful measurements of rainwater
revealed that the mercury is coming from the atmosphere, carried
to earth by rain. Mercury enters the atmosphere from two main
sources: 65% from combustion of coal, and 25% from solid waste
incineration.[3]
Recent measurements of mercury in the atmosphere over the oceans
indicate that total mercury in the atmosphere has doubled since
the 19th century. Nature moves mercury into the atmosphere by
various means, such as volcanoes, but human sources are now three
times as large as all other natural sources of mercury. That is,
humans activities (chiefly burning coal and garbage) account for
75% of the mercury entering the atmosphere today, whereas all
non-human sources account for only 25%. This new data has come as
something of a shock to scientists, who had thought humans were a
rather puny actor on this particular stage.
Economic projections by the Washington think tank, Resources for
the Future, indicate that humans are likely to double their
mercury releases during the next 50 years.[4] If that should
occur, some scientists say freshwater fish in acidic waters
everywhere will become toxic to humans.
The mercury in the atmosphere is 97% elemental mercury, but the
mercury in fish is 95% to 99% methylmercury, which is elemental
mercury with a carbon atom and three hydrogen atoms attached.
Methylmercury is much more toxic than elemental mercury.
Scientists now know that mercury becomes methylated when it
enters a body of water, especially an acidic body of water,
though the exact role of the acid is still unclear.
Big fish taken from acid waters are dangerous to humans already.
And, as other sources of protein become more expensive or come to
be regarded as unhealthful, such as red meat, eating fish becomes
more popular. The combination of more mercury entering the
atmosphere, increasing acidity of many waters because of acid
precipation (rain, snow, and even acid fog), plus increasing
consumption of freshwater fish adds up to a growing threat to
humans.
Fish are relatively insensitive to mercury, so they can build up
a level in their tissues that is toxic to humans and other fish
eaters.
Mercury mainly attacks the central nervous system, chiefly the
brain. In adults, the first symptoms of serious exposure are loss
of sensation in the extremities of the hands and around the
mouth. If exposure continues, an unsteady gait, slurred speech,
tunnel vision (concentric constriction of vision), loss of
hearing, convulsions, madness and death follow.
The effect of mercury on humans began to be understood during the
1970s. The Chisso Corporation dumped tons of mercury into
Minamata Bay, a relatively small body of water in southern Japan,
heavily contaminating local fish. Some 2900 humans were severely
injured, a third of them killed outright. Recent court cases
indicate that an additional 10,000 individuals were permanently
harmed.[5] Based on studies of adults contaminated at Minamata in
the period 1953-1968, the World Health Organization [WHO] in 1972
established 4300 nanograms per kilogram of body weight per day
(ng/kg-day) as the dose that caused poisoning; they applied a
“safety factor” of 10 and concluded that a “safe” dose would be
430 ng/kg-day.[6] (A nanogram is a billionth of a gram; a
kilogram is 1000 grams or 2.2 pounds; a gram is 1/28th of an
ounce.)
However, since that time, much new data has become available. In
northern Iraq during the winter of 1971-72, some 6530 patients
were admitted to hospital with mercury poisoning. The death of
459 of them was attributed to mercury. Careful follow-up studies
of mercury levels in hair and blood of adults, children, and
infants allowed medical researchers to establish that infants are
5 to 10 times more sensitive to mercury than adults are. Infants
exposed before birth showed severe brain damage whereas their
mothers had mild or no symptoms. The fetus is thought to be
particularly sensitive during the first months of pregnancy when
cell migration and cell division are occurring at a fast pace.
Thus the WHO “safe” level is perilously close to a mercury level
known to harm fetuses and infants.
Dr. Thomas Clarkson at University of Rochester points out that
Iraqi infants exposed before birth showed symptoms when their
pregnant mothers had daily intakes of 600 to 1100 nanograms per
kilogram. Applying the standard “safety factor” of 10, Dr.
Clarkson says the new “safe” dose should be 60 to 110 nanograms
per kilogram.[7] Roughly 40% of the American people already eat
enough freshwater fish to exceed a mercury intake of 60 ng/kg-day.
A careful survey of fish consumption (and therefore mercury
intake) of 4864 Americans by the U.S. Department of Commerce
showed that 0.1% of the American people (250,000 individuals)
exceed the WHO “safe” dose of 430 ng/kg-day. But if we accept
Clarkson’s new “safe” dose, we can calculate that roughly 40% of
the American people (100 million individuals) are today eating
levels of mercury in fish that would have to be called unsafe.[8]
Is anyone really being affected? Humans who eat a lot of
freshwater fish seem to be, and so do fish-eating birds and
mammals. In 1978 a neurological study of 592 Cree Indian people
from three bands living along James Bay in Quebec province
revealed tremors, incoordination and abnormal reflexes were
prevalent neurological abnormalities, and other major
manifestations of mercury poisoning were seen occasionally,
including astereognosis (loss of the ability to judge the form of
an object by touch) and tunnel vision (concentric constriction of
visual field).[9] Since that time, mercury in the blood of Cree
people has been cut in half by modifying their traditional diet
to reduce intake of freshwater fish, particularly big fish.
Ocean fish seem not so susceptible to mercury buildup in their
tissues, perhaps because the oceans are not acidic. Freshwater
fish are the problem.
Bass in the Florida Everglades have 4.4 parts per million of
mercury; U.S. Food and Drug Administration forbids interstate
shipment of fish containing more than 1 ppm mercury, and the
state of Minnesota has set a “safe” level in fish at 0.16 ppm,
the strictest standard of any state. Bass and other fish in the
Everglades are definitely toxic enough to pose a real threat to
predators such as ospreys, eagles and humans. Mercury has been
confirmed as the cause of death in loons and panthers in the
Everglades. Furthermore, mercury is suspected as an important
cause of the reproductive failure being witnessed now among
eagles, mink, otter and other wildlife in the Great Lakes.
The mercury problem is heavily damaging the sport fishing
industry in at least 22 states and at least two Canadian
provinces, where warnings have been issued against eating certain
species of fish from certain waters. And, as we have seen, the
problem shows every sign of growing worse.
Given that the problem is atmospheric and international, it is
not one that states can completely solve alone, though each state
could make strides by banning garbage incineration and phasing
out the burning of coal. It will take an international accord to
stem mercury poisoning. This will require leadership from the
federal government, which so far has shown no interest.
Federal energy policy officially encourages coal-burning power
plants and incineration of municipal trash, for generation of
electricity. The Edison Electric Institute estimates it would
cost $5 billion to capture mercury from the nation’s coal-burning
plants, and it might cost $10 to $30 million to fit an
incinerator with mercury-capturing gear. (Coal combustion
provides a double whammy, acidifying waters while releasing
mercury.)
Against those costs, we must weigh loss of the sport fishing
industry and damage to the central nervous systems of large
numbers of Americans, especially infants and children.
–Peter Montague, Ph.D.
===============
[1] Janet Raloff, “Mercurial Risks From Acid’s Reign,” SCIENCE
NEWS Vol. 139 (March 9, 1991), pgs. 152-156.
[7] Clarkson, cited above, pg. 958.
Descriptor terms: mercury; mercury poisoning; resources for the
future; chisso corporation; japan; world health organization;
thomas clarkson; everglades; who; fish; wildlife; water
pollution; minamata bay; drinking water;