United States
Environmental Protection
Agency
Office of Pesticides and
Toxic Substances TS-793
Washington D C 20460
vvEPA
Mercury—
what is it?
Toxics Information
Series
Mercury
Probably best known as the silvery substance in
thermometers, mercury has been refined from cinnabar
since the 15th or 16th Century B.C. Cinnabar was used
as a red paint by primitive peoples long before the
process of mercury refining was discovered.
History also chronicles the health hazards of
occupational exposure to mercury dating to the time of
the Roman conquest of Spain when criminals sentenced to
work in the Spanish quicksilver mines had a life
expectancy of only three years. However, it was the
widespread poisoning of Japanese fisherman and their
families from consumption of methyl mercury-contaminated
fish in Minamata, Japan, in the fifties, and the recent
discovery that most other mercury compounds can be
transformed into highly toxic methyl mercury in the
environment that generated widespread concern about the
health implications of the continued release of mercury
into the environment.
This Information Bulletin discusses the hazards of
mercury and what the U.S. Environmental Protection
Agency (EPA) and others are doing to protect public
health from the risk of mercury exposure.
Mercury is a heavy metal. At room temperature, in
its pure form, it is a silvery liquid which vaporizes
easily. Mercury is an important industrial metal
because of its particular properties: . uniform volume
expansion, liquidity at room temperature, electrical
conductivity, high density, low vapor pressure, ability
to alloy with almost all common metals (except iron and
platinum), and ease of vaporizing and freezing.
Over 3,000 industries utilize mercury in
manufacturing and processing. In 1973, U.S. consumption
of mercury was approximately 1,900 metric tons. Battery
manufacturing (29.9%) and chlorine-alkali production
(24%) accounted for over half; other major uses included
paints and industrial instruments. Because of the
inherent toxicity of mercury, it was, until recently,
widely used in pesticides. Its use in medicines was for
its diuretic properties as well as being used as an
antiseptic and preservative. Because other more
effective diuretics were found the mercurial use in
medicine has declined.
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Why is Mercury is a problem because of its high toxicity
mercury and the potential for human exposure. Although all
a problem? mercury compounds are toxic, methyl mercury is by far
the most toxic, and recent discoveries concerning its
production have increased concern about its potential
exposure to the public. Scientific evidence points to
the existence of a mercury cycle, where, in part,
elemental mercury and various mercury compounds are
transformed in the environment by natural biological and
chemical action into methyl mercury. This conversion
process, known as methylation, can occur in bacteria
found in waterways and in the intestine of mammals.
Since mercury is an element and therefore cannot be
broken down into harmless components, once released into
the environment, it remains available for methylation
for many years.
Approximately 80 percent of the mercury used is
eventually released back into the environment. Because
it is easily vaporized, air emissions are a major source
of human exposure, especially near sewage treatment
facilities,. The largest contributors to air emissions
are chlorine-alkali plants, followed by fossil fuels,
municipal incinerators, and mercury mines and
smelters. Waterways also receive mercury through waste
water discharges from industrial plants and municipal
sewage. Landfill disposal of wastes contribute to the
soil buildup of mercury. There is growing concern that
the use of municipal sewage sludge as fertilizer may be
compounding the problem of mercury contamination of the
soils.
Mercury taken Tnto the body through air, water and
food is absorbed in varying amounts depending on its
chemical form and the route of intake. Absorption of
mercury present in water and food varies the most, from
about 0.01 percent for elemental mercury to nearly 100
percent for methyl mercury. The major food sources of
mercury are fish and shellfish.
In the human body, mercury accumulates in the
liver, kidney, brain and blood and causes both acute and
chronic health effects depending on the form of
mercury. Acute poisoning, although seldom seen today,
can cause severe gastrointestinal damage, cardiovasular
collapse, and acute kidney failure, all of which can
result in death.
Chronic symptoms of inorganic and organo-mercury
compounds which are most often seen industrial workers
and in cases of contaminated food consumption may
include birth defects, and central nervous system and
kidney damage. Genetic damage is also suspected. Loss
of appetite and weight loss are often the first signs of
chronic mercury poisoning.
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What is the
government
about?
this
hazard?
Nervous system damage; The most universal effects
of mercury are damage to the nervous system,, Increased
excitability, mental instability, apathy and a tendency
to weep which are often followed by fine tremors in the
hands and feet after exposure to mercury vapor.
Personality changes such as timidity, nervousness and
dizziness or insomnia may also occur. Symptoms of
methyl mercury poisoning include tunnel vision, loss of
muscle coordination, hearing impairment and impairment
of gait.
Kidney damage; Inorganic mercury causes a
transient kidney condition evidenced by excessive
protein in the urine. The condition does not occur in
all persons exposed to toxic doses of mercury. Although
we do not know what level causes kidney failure, "high"
levels almost always do.
Birth defects; Infants prenatally exposed to
methyl mercury compounds ingested by their mothers have
been born with primarily neurological defects. Symptoms
include mental disturbance, poor muscle coordination,
gait impairment, speech difficulties, and difficulties
in chewing and swallowing.
Genetic effects; In laboratory tests with insects
and plants mercury has been shown to cause chromosomal
damage similar to that which causes Downs Syndrome
(mongolism) in humans. Scientists are concerned that
mercury may cause similar damage in humans, resulting in
congenital disorders and possibly cancer, although it
has yet to be documented.
Recognizing the toxic effects of mercury, the
Federal government has taken steps to reduce the doing
public's exposure to the chemical and its compounds.
EPA has issued effluent guidelines for industry to
reduce the release of mercury into water, and is
preparing final water quality criteria for mercury.
Based on the latest scientific information, the criteria
can be used for further regulation of mercury by the
Agency or individual states. Both effluent guidelines
and water quality criteria are authorized by the Clean
Water Act, administered by EPA.
Under the authority of the Clean Air Act, EPA is
reviewing the current national air emission standards
for mercury together with several other hazardous
substances, in order to reduce the risk of mercury
exposure through the ambient air. More importantly,
under the Clean Air Act, EPA has limited emissions of
mercury from certain industries. As hazardous waste,
under the provisions of the Resource Conservation and
Recovery Act, certain mercury wastes are regulated by
EPA from point of origin to final disposal.
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In February 1976 EPA ordered an immediate halt to
the production, sale and use of most mercurial
pesticideso Subsequent to resulting litigation, the
original cancellation order was modified to allow
registration under the Federal Insecticide, Fungicide
and Rodentcide Act of mercurial pesticides only for a
few fungicidal uses, such as in-can preservatives in
latex paints, mildew inhibitors on outdoor fabrics and
in outdoor paints, control of brown mold on lumber,
control of winter turf diseases, and control of Dutch
Elm Disease (currently being reconsidered).
Because of the risk to workers in industries
utilizing mercury, the Occupational Safety and Health
Administration is reviewing the current occupational
exposure standard of 0.1 milligrams of mercury per cubic
meter of air (0.1 mg/m ) to determine whether or not
that standard should be reduced to 0.05 mg/m3 to assure
protection of the workers. The Food and Drug
Administration (FDA) is developing methods to determine
the concentration of methyl mercury in fish and other
foodso In order to protect the public from contaminated
fish, the FDA has issued an action level of 1.0 part
mercury per million parts fish (1 ppm) in fish and
shellfish as the maximum amount of mercury it will allow
in those foods.
Research is continuing to define more clearly the
tolerable levels of exposure to mercury, the health
effects of increased burning of coal and the effects of
chronic exposure to low levels of mercury compounds on
unborn children. Results of this research will enable
regulatory agencies to better assess the threat to
public health and to institute appropriate control
measures,
In Summary; The toxic effects of mercury, although
not completely defined, are of grave concern, as is the
continued release of mercury to the environment where it
can remain and affect future generations. The Federal
government has taken several steps to reduce the
public's exposure to mercury, and is investigating means
to further reduce the mercury risk in this country.
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CHILDREN AT RISK
As in the case with other toxic chemicals such as
lead, children are especially susceptible to the adverse
effects of methylmercury. Methlymercury easily crosses
the placental barrier and concentrates in the fetus more
readily than in the mother. Thus, a woman exposed to
toxic levels of mercury may not exhibit any signs of
mercury poisoning, but her child may be born with brain
damage quite similar to cerebral palsy*
Children may also react adversely to mercury
exposure after they are born. Mercury can be
transmitted through breast milk, as well as through the
environmental media of air, water and food. Neuro-
logical symptoms are very similar to those seen in
adults. In addition, children may develop dermatitis,
eczyma and mucous membrane irritation. Acrodynia, or
"pink disease™ affects only children from four months to
four years of age. Characterized by a distinctive rash;
coldness, swelling and irritation of the hands, feet,
cheeks and nose, usually followed by peeling and
ulceration; typical neurological and psychological
symptoms, and profuse perspiration, acrodynia has been
almost totally eradicated by withdrawal of mercury from
common medications used in children (cough medicines,
ointments, antiseptics, etc.).
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