Why Is Mercury Important?
What Is Mercury?
Mercury, also known as quicksilver because
it is a silver-colored liquid at room temperature, is
an element that does not break down. It occurs naturally
and is found in very small amounts in oceans, rocks
and soils. It becomes airborne when rocks erode, volcanoes
erupt and soil decomposes. It then circulates in the
atmosphere and is redistributed throughout the environment.
Large amounts of mercury also become airborne when coal,
oil or natural gas is burned as fuel or mercury-containing
garbage is incinerated. Once in the air, mercury can
fall to the ground with rain and snow, landing on soils
or water bodies, causing contamination.
Lakes and rivers are also contaminated
when there is a direct discharge of mercury-laden industrial
waste or municipal sewage. Once present in these water
bodies, mercury accumulates in fish and may ultimately
reach the dinner table.
Although mercury has been a very
useful element, due to its unique properties, it poses
a very real health risk-from direct exposure to mercury,
as well as from eating contaminated fish. We can minimize
this risk by reducing our use of mercury-containing
products and properly disposing of mercury-containing
How Is Mercury
Released from Human Activities?
Mercury has been used for hundreds, if
not thousands, of years for a wide variety of purposes.
Historical uses, which are no longer prevalent, include:
preparing felt for hats, controlling mildew in paints,
killing weeds as a component of herbicides, and various
medical uses-teething powder, antiseptic ointments and
syphilis treatment. Its toxic effects on workers in
hat factories in the late 1800's led to the term "mad
as a hatter." Mercury is still used for folk medicine
and ceremonial purposes in several cultures.
Today, mercury is released to the environment
from many sources. It is still used in household and
commercial products, as well as industrial processes.
Coal-fired power plants, incinerators, some manufacturing
plants, hospitals, dental offices, schools and even
homes have all been found to release mercury. In the
home, mercury can be found in fluorescent lights, thermostats,
thermometers, and even some children's toys. At school,
mercury may be in science and chemistry classrooms,
the nurse's office and electrical systems.
here to see a demonstration on how mercury is vaporized.
Two different forms of mercury are of
greatest human health concern. Elemental mercury, which
is most toxic in its vapor form, slowly vaporizes at
room temperature and more quickly when heated. Breathing
the invisible vapor from mercury spilled in carpeting,
furniture or other surfaces can seriously poison children
playing with or near elemental mercury.
Mercury easily enters the body through
several routes, but it may take many months for the
body to purge itself of the poisonous metal. Mercury
vapors can be breathed - among the most hazardous exposures
to elemental mercury. Handling the liquid metal also
allows mercury to enter the body through pores of the
skin. Mercury leaves the body mostly through the urinary
and digestive tracts.
Elemental and inorganic mercury salts
can be transformed into organic mercury by the bacteria
in the bottom mud in water bodies. Unlike elemental
mercury, organic mercury (often referred to as "methylmercury")
can be readily absorbed in humans. The most likely source
of methylmercury is eating contaminated fish. Human
exposure to methylmercury can result in long-lasting
health effects, especially on fetal development during
pregnancy. In addition, mercury poisoning has been linked
to nervous system, kidney and liver damage and impaired
childhood development. Nervous system disorders include
impaired vision, speech, hearing and coordination.
|Symptoms of Mercury Poisoning:
- Impairment of the peripheral vision
- Disturbances in sensations ("pins and
needles" feelings, numbness) usually in
the hands feet and sometimes around the mouth
- Lack of coordination of movements, such as
- Impairment of speech, hearing, walking;
Mercury in the
Mercury is an environmental problem around
the world. States with many lakes are especially aware
of this because one of the most serious ways people
are exposed to mercury is through eating contaminated
Organic mercury tends to increase up the
food chain, particularly in lakes. The mud at the bottom
of a lake may have 100 or 1000 times the amount of mercury
than is in the water. Worms and insects in the mud extract
and concentrate the organic mercury. Small fish that
eat these critters further concentrate the mercury in
their bodies. This concentration process, known as "bioaccumulation",
continues as larger fish eat smaller fish until the
top predator fish in the lake have methylmercury levels
in their tissues that are up to 1,000,000 times the
level in the water in which they live.
Over 40 states in the U.S. and several
Canadian provinces advise anglers and their families
to reduce their consumption of certain types of fish
taken from various lakes and streams due to their high
mercury content. Certain types of store bought fish
also have elevated mercury levels, including swordfish