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Symptoms and Signs of Mercury Poisoning

Doctor's Notes on Mercury Poisoning

Mercury is an element that exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Fish and shellfish are the main sources of methylmercury exposure in humans due to a highly toxic form of mercury (methylmercury) that accumulates in the tissues of fish, shellfish and animals that eat fish.

High levels of exposure to mercury can damage the brain, kidneys, heart, lungs, and immune function. High levels of methylmercury in pregnant women and young children may harm the infant or child’s developing nervous system. Symptoms associated with methylmercury poisoning include impairment of peripheral vision, sensory disturbances, coordination problems, speech impairment, and muscle weakness. Symptoms associated with elemental mercury poisoning can include tremors, muscle atrophy, twitching, insomnia, and emotional changes.

Medical Author:
Medically Reviewed on 3/11/2019

Mercury Poisoning Symptoms

Symptoms of mercury poisoning can be numerous and may occur either rapidly or over long periods of time. In general, symptoms occur and progress more rapidly the higher the dose of mercury encountered. Exposure to the various forms of mercury can result in some similar and some different symptoms. Symptoms can be grouped into three categories based on the form of mercury toxicity: 1) elemental and vaporized mercury, 2) organic mercury, and 3) inorganic mercury.

Elemental and Vaporized Mercury Poisoning Symptoms

Elemental mercury toxicity (which usually occurs in the vaporized form) can cause:

  • mood swings, nervousness, irritability, and other emotional changes,
  • insomnia,
  • headache,
  • abnormal sensations,
  • muscle twitching,
  • tremors,
  • weakness,
  • muscle atrophy, and
  • decreased cognitive functions.

High exposures of elemental mercury can cause kidney malfunction, respiratory failure, and death.

Organic Mercury Poisoning Symptoms

Organic mercury toxicity (most frequently in the methylmercury form from ingestion), causes neurological malfunctions, and especially in a fetus, impaired neurological development. Other symptoms include:

  • peripheral vision impairment,
  • stinging or needle-like sensations in the extremities and mouth,
  • loss of coordination,
  • muscle weakness, and
  • other impairments of speech and hearing.

Since many pregnant women have had methylmercury toxicity, the effects of this toxicity on their children was studied. Importantly, the fetal brain was shown to be very sensitive to methylmercury; developmental impairments such as reduced ability in thinking, attention span, memory, and most motor skills occurred in various degrees, often severe, even if the mother developed few if any symptoms.

Inorganic Mercury Poisoning Symptoms

Inorganic mercury toxicity often causes skin rashes and inflammation (dermatitis). If ingested, it can dissolve tissues and some may be absorbed by the intestinal tissue. Large amounts of ingested inorganic mercury may cause bloody diarrhea. Absorbed mercury can spread to other organ systems resulting in mental changes including mood swings and memory loss or renal damage. Muscle weakness may also occur.

Other Mercury Poisoning Symptoms

Many other symptoms and health problems have been attributed to mercury poisoning (for example, high blood pressure, endometriosis, headaches) in anecdotal reports in the popular press and in a few case reports in scientific publications. Currently, there are no good studies to support these claims; however, if people have concerns about their symptoms and health problems related to mercury exposure, they should discuss their concerns with their doctor.

Mercury Poisoning Causes

Mercury binds to sulfhydryl groups in many tissue enzymes and proteins, and thereby causes direct damage to cells and their functions. This damage can be drastic and eventually precipitate failure of organ systems such as the lungs, kidneys or the nervous system.

Outbreaks of mercury poisoning usually occur when there is an industrial release of mercury or methylmercury into the environment. The classic example of such a disaster is the contamination of Minamata Bay in Japan, where the term Minamata disease originated. Studies from about 1956 to 1960 suggested the unusual symptoms (neurological) found in people in this area could be traced back to industrial wastewater containing methylmercury. Over 2,200 people were diagnosed and over 1,700 deaths were eventually attributed to methylmercury toxicity. Mercury has been used in skin creams. The most recent problem cream was identified in 1996 from Mexico named "Crèma de Belleza-Manning."

Mercury poisoning can be caused by all forms of mercury (elemental, vapor, inorganic, and organic). Poisoning of humans can occur from inhalation, ingestion, or skin contact with the various forms of mercury.

Inhalation Mercury Poisoning

Inhalation poisoning occurs when elemental mercury is vaporized, usually in a closed indoor space, when products such as thermometers, medical equipment, valves or other products are broken open and elemental mercury escapes. Any heating of elemental mercury increases its rate of vaporization (slow vaporization occurs at room temperature) which worsens inhalation exposure.

Ingestion and Skin Contact Mercury Poisoning

Ingestion is one of the most frequent ways in which people get mercury poisoning; and mercury is most frequently ingested in the organic methylmercury form of mercury. Methylmercury (also termed methyl mercury, monomethylmercury or monomethylmercuric cation) is generated by two general processes; as an industrial production byproduct and microbially produced when elemental and vaporized mercury eventually reaches water. Unfortunately, methylmercury enters the tissues of fish (and shellfish) where it remains. The more methylmercury that is present in the environment, the higher the concentration in the fish tissue. Methylmercury is not cleared out of fish tissue; the older and larger the fish, especially those fish that eat other fish (for example, shark, sailfish, tuna, and marlin) the higher the methylmercury levels can be in their tissue. People that eat a lot of these fish may get mercury poisoning.

Inorganic mercury (for example, mercury compounds in batteries) most frequently causes human toxicity when ingested or adsorbed by the skin. Many inorganic mercury compounds are caustic (dissolve tissue).

Uncommon and Common Food-Poisoning Dangers in Pictures Slideshow

Uncommon and Common Food-Poisoning Dangers in Pictures Slideshow

Listeria bacteria can contaminate fresh produce, like cantaloupes, as well as some processed foods, like cheeses. Symptoms of infection include fever, muscle aches, upset stomach, or diarrhea -- occurring 2 days to 2 months after exposure.

Safety: Scrub raw produce and dry before cutting. Store in fridge below 40 F. Clean everything in contact with a whole melon.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.