Mercury Poisoning (cont.)
What are the health effects and symptoms of mercury exposure
or poisoning?
People in the U.S. are mainly exposed to methylmercury, an organic compound,
when they eat fish and shellfish that contain methylmercury. Whether an exposure
to the various forms of mercury will harm a person's health depends on a number
of factors (below). Almost all people have at least trace amounts of
methylmercury in their tissues, reflecting methylmercury's widespread presence
in the environment and people's exposure through the consumption of fish and
shellfish. People may be exposed to mercury in any of its forms under different
circumstances. The factors that determine how severe the health effects are from
mercury exposure include these:
- the chemical form of mercury;
- the dose;
- the age of the person exposed (the
fetus is the most susceptible);
- the duration of exposure;
- the route of exposure
-- inhalation, ingestion, dermal contact, etc.; and
- the health of the person
exposed.
Mercury exists in three chemical forms. They each have specific effects
on human health.
- Methylmercury
- Elemental mercury
- Other mercury compounds (inorganic and
organic)
Methylmercury effects
For fetuses, infants, and children, the primary
health effect of methylmercury is impaired neurological development.
Methylmercury exposure in the womb, which can result from a mother's consumption
of fish and shellfish that contain methylmercury, can adversely affect a baby's
growing brain and nervous system. Impacts on cognitive thinking, memory, attention,
language, and fine motor and visual spatial skills have been seen in children
exposed to methylmercury in the womb. Recent human biological monitoring by the
Centers for Disease Control and Prevention in 1999 and 2000 (PDF) shows that most people have blood mercury levels below a level
associated with possible health effects.
More recent data from the CDC support this general finding.
Outbreaks of methylmercury poisonings have made it clear
that adults, children, and developing fetuses are at risk from ingestion
exposure to methylmercury. 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.
For more information on fish consumption advisories across the country, visit
EPA's fish consumption web pages.
Symptoms of methylmercury poisoning
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.
Elemental mercury effects
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 of elemental mercury effects
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.
Effects of other mercury compounds (inorganic and organic)
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
Symptoms of high exposures to inorganic mercury include:
People concerned about their exposure to inorganic mercury should consult their
physician.
Next: What about mercury in batteries? »
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