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Mercury in the Environment (9/29/2010)

Methylmercury is very toxic to living organisms. Although only 10% of the mercury in water is methylmercury, methylmercury is very soluble, mobile, and bioaccumulative. Bioaccumulation is the process by which organisms take up a contaminant more rapidly than their bodies can eliminate it. Thus, mercury accumulates in the body over time. If mercury is continually ingested it can build up to toxic levels. Mercury becomes even more hazardous to organisms higher in the food chain because it biomagnifies. Biomagnification is the incremental increase in a contaminant’s concentration at each level of the food chain. For example, humans eat large fish, which eat lots of small fish, which eat lots of plants. Mercury bioaccumulates in every organism along the way, and the human will ingest all of the mercury accumulated during each step.

Wildlife Health Impacts

Wildlife is exposed to mercury primarily in their diet. Some known effects that mercury has on wildlife include:

  • Reproductive failure
  • Impaired muscular coordination
  • Behavioral abnormalities (e.g. running in circles)
  • Abnormal vocalization
  • Vertigo
  • Convulsions
  • Paralysis
  • Death

Human Health Impacts

Although some human exposure to mercury is short-term due to mercury-containing equipment breakage and spills (acute exposure), most exposure occurs through regular consumption of fish contaminated with methylmercury (chronic exposure). Wisconsin has issued a statewide fish consumption advisory for all inland waters due to mercury contamination. Mercury may build up and affect the nervous system of adults if large amounts of fish contaminated with mercury are consumed. Studies of health effects of eating fish containing mercury have found that fetuses and children are more sensitive because mercury can affect the developing brain and nervous systems. Health effects of mercury due to fish consumption are subtle and difficult to recognize.

Chronic Exposure

In adults, chronic exposure to methyl mercury affects the Central Nervous System (CNS) and symptoms may include:

  • sleep disturbances
  • irritability
  • memory loss
  • behavior changes
  • paresthesia - a sensation of pricking on the skin
  • blurred vision
  • malaise - a vague feeling of illness or depression
  • speech difficulties
  • constriction of the visual field
  • deafness

In children, effects may include:

  • impaired dexterity
  • impaired fine motor skills
  • impaired verbal memory
  • delayed development

Infants born to women who ingested high concentrations of methyl mercury have been shown to exhibit CNS effects such as:

  • mental retardation
  • ataxia - loss or lack of muscular coordination
  • deafness
  • constriction of the visual field
  • blindness
  • cerebral palsy

At lower methyl mercury concentrations, infants may exhibit symptoms such as:

  • developmental delays
  • abnormal reflexes

Following the fish consumption advice allows people to obtain the health benefits of eating fish while reducing their risk of exposure to environmental contaminants in fish.

Acute Exposure

Acute (short-term) exposure to mercury can occur three different ways: inhalation of elemental mercury, oral exposure to inorganic mercury, and the very rare case of inhalation of high levels of methyl mercury. Each route of exposure leads to different health effects. Call the 24-hour toll free poison hotline at 1-800-222-1222 if you've been exposed to mercury.

Acute exposure to high levels of elemental mercury affects the Central Nervous System (CNS) and kidneys and can cause symptoms such as:

  • tremors
  • irritability
  • insomnia
  • memory loss
  • neuromuscular changes
  • headaches
  • slowed sensory and motor nerve function
  • reduction in cognitive function

Acute oral exposure to inorganic mercury compounds may lead to symptoms such as:

  • metallic taste in the mouth
  • nausea
  • vomiting
  • severe abdominal pain

Acute inhalation exposure due to high levels of methyl mercury (very rare) can result in health effects such as:

  • blindness
  • deafness
  • impaired level of consciousness

Most of the health effect information contained on this page was taken from information provided by the U.S. EPA at: Mercury Compounds.

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