Mercury
Bacteria in soils and sediments convert mercury to methylmercury. In this form, it is taken up by tiny aquatic plants and
animals.
Mercury:
Under part 503, EPA will allow 57 ppm of mercury to be sprayed on famland, with a total disposal of 17 kilograms per
hectare. That is assuming that anyone keeps track. In Kansas City they did not record the mercury on the reports.
Bacteria in soils and sediments convert mercury to methylmercury. In this form, it is taken up by tiny aquatic plants and
animals. Fish that eat these organisms build up methylmercury in their bodies. As ever-bigger fish eat smaller ones, the
methylmercury is concentrated further up the food chain. This process is called "bioaccumulation
it is estimated that more than 300,000 newborns each year may have increased risk of learning disabilities associated
with in utero exposure to methylmercury. More recent data from the CDC support this general finding
Depending on these factors, atmospheric mercury can be transported over a range of distances before it is deposited,
potentially resulting in deposition on local, regional, continental and/or global scales. Mercury that remains in the air for
prolonged periods of time and travels across continents is said to be in the "global cycle."
Typically, mercury is released into the atmosphere in one of three forms:
- elemental mercury: can travel a range of distances, may remain in the atmosphere up to one year and may travel
globally before undergoing transformation
- particle-bound mercury: can fall out of the air over a range of distances
- oxidized mercury (sometimes called ionic or reactive gaseous mercury (RGM)): found predominantly in water-
soluble forms, which may be deposited at a range of distances from sources depending on a variety of factors
including topographic and meteorologic conditions downwind of a source.
Elemental (metallic) mercury primarily causes health effects when it is breathed as a vapor where it can be absorbed
through the lungs. These exposures can occur when elemental mercury is spilled or products that contain elemental
mercury break and expose mercury to the air, particularly in warm or poorly-ventilated indoor spaces. Symptoms include
these: tremors; emotional changes (e.g., mood swings, irritability, nervousness, excessive shyness); insomnia;
neuromuscular changes (such as weakness, muscle atrophy, twitching); headaches; disturbances in sensations;
changes in nerve responses; performance deficits on tests of cognitive function. At higher exposures there may be
kidney effects, respiratory failure and death. People concerned about their exposure to elemental mercury should
consult their physician.
During these poisoning outbreaks some mothers with no symptoms of nervous system damage gave birth to infants with
severe disabilities, it became clear that the developing nervous system of the fetus may be more vulnerable to
methylmercury than is the adult nervous system.
In addition to the subtle impairments noted above, symptoms of methylmercury poisoning may include; impairment of the
peripheral vision; disturbances in sensations ("pins and needles" feelings, usually in the hands, feet, and around the
mouth); lack of coordination of movements; impairment of speech, hearing, walking; and muscle weakness. People
concerned about their exposure to methylmercury should consult their physician.
High exposures to inorganic mercury may result in damage to the gastrointestinal tract, the nervous system, and the
kidneys. Both inorganic and organic mercury compounds are absorbed through the gastrointestinal tract and affect
other systems via this route. However, organic mercury compounds are more readily absorbed via ingestion than
inorganic mercury compounds. Symptoms of high exposures to inorganic mercury include: skin rashes and dermatitis;
mood swings; memory loss; mental disturbances; and muscle weakness. People concerned about their exposure to
inorganic mercury should consult their physician. (35)
1.6 How can mercury affect children?
This section discusses potential health effects from exposures during the period from conception to maturity at 18 years
of age in humans. Potential effects on children resulting from exposures of the parents are also considered.
Children are at risk of being exposed to metallic mercury that is not safely contained, to mercury that may be brought
home on work clothes or tools, or to methylmercury-contaminated foods. Methylmercury eaten or swallowed by a
pregnant woman or metallic mercury that enters her body from breathing contaminated air can also pass into the
developing child. Inorganic mercury and methylmercury can also pass from a mother's body into breast milk and into a
nursing infant. The amount of mercury in the milk will vary, depending on the degree of exposure and the amount of
mercury that enter the nursing woman's body. There are significant benefits to breast feeding, so any concern that a
nursing woman may have about mercury levels in her breast milk should be discussed with her doctor. Methylmercury
can also accumulate in an unborn baby's blood to a concentration higher than the concentration in the mother.
For similar exposure routes and forms of mercury, the harmful health effects seen in children are similar to the effects
seen in adults. High exposure to mercury vapor causes lung, stomach, and intestinal damage and death due to
respiratory failure in severe cases. These effects are similar to those seen in adult groups exposed to inhaled metallic
mercury vapors at work.
Children who had been exposed to excessive amounts of mercurous chloride tablets for worms or mercurous chloride-
containing powders for teething discomfort had increased heart rates and elevated blood pressure. Abnormal heart
rhythms were also seen in children who had eaten grains contaminated with very high levels of methylmercury.
Other symptoms of poisonings in children who were treated with mercurous chloride for constipation, worms, or teething
discomfort included swollen red gums, excessive salivation, weight loss, diarrhea and/or abdominal pain, and muscle
twitching or cramping in the legs and/or arms. Kidney damage is very common after exposure to toxic levels of inorganic
mercury. Metallic mercury or methylmercury that enters the body can also be converted to inorganic mercury and result
in kidney damage.
Children who breathe metallic/elemental mercury vapors, eat foods or other substances containing phenylmercury or
inorganic mercury salts, or use mercury-containing skin ointments for an extended period may develop a disorder known
as acrodynia, or pink disease. Acrodynia can result in severe leg cramps; irritability; and abnormal redness of the skin,
followed by peeling of the hands, nose, and soles of the feet. Itching, swelling, fever, fast heart rate, elevated blood
pressure, excessive salivation or sweating, rashes, fretfulness, sleeplessness, and/or weakness may also be present. It
was once believed that this syndrome occurred only in children, but recent reported cases in teenagers and adults have
shown that they can also develop acrodynia.
In critical periods of development before they are born, and in the early months after birth, children and fetuses are
particularly sensitive to the harmful effects of metallic mercury and methylmercury on the nervous system. Harmful
developmental effects may occur when a pregnant woman is exposed to metallic mercury and some of the mercury is
transferred into her developing child. Thus, women who are normally exposed to mercury vapors in the workplace (such
as those working in thermometer/barometer or fluorescent light manufacturing or the chlor-alkali industry) should take
measures to avoid mercury vapor exposures during pregnancy. Exposures to mercury vapors are relatively rare outside
of the workplace, unless metallic mercury is present in the home.
As with mercury vapors, exposure to methylmercury is more dangerous for young children than for adults, because
more methylmercury easily passes into the developing brain of young children and may interfere with the development
process.
Methylmercury is the form of mercury most commonly associated with a risk for developmental effects. Exposure can
come from foods contaminated with mercury on the surface (for example, from seed grain treated with methylmercury to
kill fungus) or from foods that contain toxic levels of methylmercury (as in some fish, wild game, and marine mammals).
Mothers who are exposed to methylmercury and breast-feed their infant may also expose the child through the milk. The
effects on the infant may be subtle or more pronounced, depending on the amount to which the fetus or young child was
exposed. In cases in which the exposure was relatively small, some effects might not be apparent, such as small
decreases in IQ or effects on the brain that may only be determined by the use of very sensitive neuropsychological
testing. In instances in which the exposure is great, the effects may be more serious. In some such cases of mercury
exposure involving serious exposure to the developing fetus, the effects are delayed. In such cases, the infant may be
born apparently normal, but later show effects that may range from the infant being slower to reach developmental
milestones, such as the age of first walking and talking, to more severe effects including brain damage with mental
retardation, incoordination, and inability to move. Other severe effects observed in children whose mothers were
exposed to very toxic levels of mercury during pregnancy include eventual blindness, involuntary muscle contractions
and seizures, muscle weakness, and inability to speak. It is important to remember, however, that the severity of these
effects depends upon the level of mercury exposure and the length of exposure. The very severe effects just mentioned
were reported in large-scale poisoning instances in which pregnant and nursing women were exposed to extremely high
levels of methylmercury in contaminated grain used to make bread (in Iraq) or seafood (in Japan) sold to the general
population.
Researchers are currently studying the potential for less serious developmental effects, including effects on a child's
behavior and ability to learn, think, and solve problems that may result from eating lower levels of methylmercury in
foods. A main source of exposure to methylmercury for the pregnant woman and the young child is from eating fish.
Most fish purchased in the market in the United States do not have mercury levels that pose a risk to anyone, including
pregnant women. Since mercury accumulates in the muscles of fish, larger fish that feed on smaller fish and live for long
periods usually have larger concentrations of methylmercury than fish that feed on plants. For example, shark and
swordfish normally contain the highest levels of mercury out of all ocean fish. Scientists have an ongoing debate about
the value of fish in the diet versus any risk from increased exposure of pregnant women to methylmercury that may be in
the fish. The safety of most fish sold commercially in the United States is regulated by the FDA. These fish pose no
health risk to those who purchase and eat them. Only fish or wildlife containing relatively high levels of methylmercury
are of concern
http://www.atsdr.cdc.gov/toxprofiles/phs46.html