Mercury has been in the news a lot recently, mostly as a result of its toxic environmental effects. The largest sources of
mercury in the environment are coal-fired power plants and municipal waste incinerators, used throughout the U.S., but particularly in the
Midwest. These plants emit mercury into the air (as well as sulfur dioxide and other air pollutants), where it wafts on air currents over
to the lakes and rivers of upstate New York, New England and our neighbors to the north in Canada. There it ends up accumulating in fish,
sometimes in the form of highly toxic methyl mercury after digestion by bacteria in the waters. Also, the run-off from the power plants
and incinerators pollutes the waters near them with mercury. This pollution harms not only humans, but wreaks havoc with birds and some
fish and frog species.
But what many people dont realize is that mercury remains a serious workplace hazard. Mercury is heavily used in the
chlor-alkali industry for electrolytic production of chlorine and caustic soda. It is also still used to make high-intensity lamp bulbs
and in fluorescent lights. These lighting uses pose a serious potential hazard to plant and building maintenance crews, who regularly
replace fluorescent fixtures and clean up after these break. Also liquid mercury is used in high-power electrical switches, such as those
used by electric utilities and railway power systems.
Liquid mercury is used widely in industrial and medical facilities in thermometers, manometers (pressure gauges) and
barometers. It is also used widely for experiments in physics and chemistry labs in high schools and colleges. The main danger in all of
these uses is not so much exposure when the mercury is in use, but when droplets of mercury get spilled on the floors and accumulate in
cracks in the floor tiles and behind furniture. This doesnt look or sound dramatic, but the mercury just sits there for years and emits
vapors into the lab and adjoining classrooms, affecting teachers, students and cleaning employees.
MERCURY IN THE BLOOD
Several years ago a major study in several hospitals in New York City found dangerous levels of mercury in the blood and
urine of hospital workers who repair and recharged the blood-pressure machines, still widely used in hospitals, nursing homes and doctors
offices. Often routine air testing in school labs turns up high mercury levels on lab benches and prep rooms.
For decades liquid mercury metal and mercury compounds were used extensively, if not promiscuously, in a host of
industrial processes, such as light bulb manufacturing, reflecting surfaces for mirrors, and as a fungicide and biocide in paints and
paper. While many of these uses have been discontinued or reduced, plants which used to make these products have often since been
converted to other industrial and residential uses. For example, in Newark, N.J., an old high-intensity light bulb manufacturing plant,
used in WWII, was abandoned by GE and later sold to a group of artists for homes and studios. Many of the residents later became ill, and
after investigation, the place was found to be hopelessly polluted with mercury from the old manufacturing plant. Eventually, the building
had to be abandoned and torn down it was just not possible to get rid of enough of the old mercury soaked into the building to make it
habitable.
WHAT ARE THE EFFECTS?
In workplaces today, most of the harmful effects of mercury are caused by long-term, low-level exposures, called chronic
exposures. The main target organs of this exposure are the kidneys, and this exposure can cause serious kidney damage. Many persons on
kidney dialysis are, without knowing it, suffering from the long-term effects of mercury and/or lead overexposure.
Chronic exposure to mercury can also cause nervous system disorders, again much like those caused by lead. Declines in
muscular coordination, more frequent mood swings, impaired nerve conduction and memory loss can result. Some persons show fine tremors of
the fingers, hands or arms. Also, some persons develop allergic skin sensitization to mercury and mercury compounds. Mercury exposure does
not appear to cause cancer, based on the limited studies done so far. The main route of entry of mercury is by inhalation, although some
mercury can enter the body through the skin.
Of special concern are possible reproductive effects from mercury exposure. There is no question that mercury and mercury
compounds can cross the placenta and expose the fetus in utero. However, the effects of this mercury exposure on the fetus are not
clear. As a matter of caution, pregnant women should avoid exposure to mercury (and, of course, lead). The U.S. Food and Drug Agency (FDA)
issued an advisory warning to pregnant women last year not to eat swordfish, king mackerel, shark and tilefish while pregnant, since
methyl mercury appears to accumulate in these types of fish. As a matter of public health caution, it also advised nursing mothers and
young children not to eat these fish as well.
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