Mercury Exposure: Causes, Symptoms and Treatment

What is Mercury Exposure?

Mercury is a naturally occurring heavy metal found in several chemical forms: elemental mercury, inorganic mercury compounds, and organic compounds such as methylmercury. Mercury exposure occurs when the human body absorbs mercury through food, air, water, or skin contact, and concentrations reach levels harmful to health. Mercury is classified as one of the most toxic heavy metals and is recognized as neurotoxic (damaging to the nervous system), nephrotoxic (damaging to the kidneys), and immunotoxic.

Causes and Sources of Mercury Exposure

Mercury is present in the environment through both natural processes and human activity. The most common sources of exposure include:

• Fish consumption: Large predatory fish such as tuna, swordfish, shark, and marlin frequently contain high levels of methylmercury due to biological accumulation (bioaccumulation) in the food chain.
• Dental amalgam fillings: Dental amalgams contain elemental mercury. Small amounts may be released during chewing or tooth brushing.
• Industrial emissions: Coal-fired power plants, waste incineration facilities, and the chlor-alkali industry are significant sources of mercury emissions into the environment.
• Certain medical devices and instruments: Older thermometers, blood pressure monitors, and some vaccines (thimerosal) may contain mercury.
• Skin care products: Some illegally marketed skin-lightening creams and cosmetics contain mercury compounds.
• Artisanal gold mining: In developing countries, mercury is widely used in gold extraction, causing significant environmental and health burdens.

Symptoms of Mercury Exposure

The symptoms of mercury exposure depend largely on the type of mercury compound, the dose, and the duration of exposure. A distinction is made between acute and chronic poisoning.

Acute Mercury Poisoning

• Severe cough and shortness of breath (when inhaling mercury vapor)
• Nausea, vomiting, and diarrhea
• Metallic taste in the mouth
• Inflammation of the gums and tooth loss
• Kidney damage, potentially leading to kidney failure

Chronic Mercury Exposure

• Neurological symptoms: Tremors, memory problems, difficulty concentrating, mood swings, and personality changes
• Sensory disturbances: Tingling or numbness in the hands and feet
• Visual disturbances and hearing loss
• Muscle weakness and coordination problems
• Fatigue and general malaise
• In children: developmental delays and behavioral issues

High-Risk Groups

Certain population groups are particularly sensitive to mercury:

• Pregnant women: Methylmercury can cross the placenta and seriously impair the brain development of the unborn child.
• Infants and young children: The developing nervous system is especially vulnerable to mercury.
• People with kidney disease: The kidneys are a primary target organ for inorganic mercury.
• Individuals with frequent fish consumption, particularly from contaminated waters.

Diagnosis

The diagnosis of mercury exposure is established through various methods:

• Blood test: Provides information about acute or recent exposure, as mercury is cleared from the blood relatively quickly.
• Urine analysis: Suitable for detecting chronic exposure to inorganic or elemental mercury.
• Hair analysis: Particularly useful for assessing methylmercury exposure over a longer period, as mercury is incorporated into the hair structure.
• Neurological examinations: Imaging techniques (MRI) and neurological tests may be used when nerve damage is suspected.

Treatment and Therapy

Treatment of mercury exposure depends on the severity and type of exposure:

Reduction of Exposure

The first and most important step is to stop further mercury intake, for example by avoiding contaminated foods, removing amalgam fillings (only by a specialized dentist), or changing the work environment.

Chelation Therapy

In cases of clinically significant poisoning, so-called chelating agents are used. These substances bind mercury in the body and enable its excretion through the kidneys. Agents used include DMPS (dimercaptopropanesulfonate) and DMSA (dimercaptosuccinic acid). Chelation therapy should only be carried out under medical supervision.

Symptomatic Treatment

Supportive measures include treatment of impaired kidney function, neurological damage, and other secondary conditions. In cases of severe acute poisoning, intensive medical care may be required.

Prevention

To minimize the risk of mercury exposure, health authorities recommend the following measures:

• Limit consumption of fish with high mercury content (tuna, swordfish, shark), especially for pregnant women and children
• Use only certified and regulated cosmetics and skin care products
• Dispose of mercury thermometers and old measuring devices safely
• Follow workplace safety regulations when handling mercury
• Regular monitoring of mercury levels in occupationally exposed individuals

References

1. World Health Organization (WHO): Mercury and health. Fact sheet. Geneva, 2017. Available at: https://www.who.int/news-room/fact-sheets/detail/mercury-and-health
2. European Food Safety Authority (EFSA): Scientific opinion on the risk for public health related to the presence of mercury and methylmercury in food. EFSA Journal. 2012;10(12):2985.
3. Clarkson TW, Magos L: The toxicology of mercury and its chemical compounds. Critical Reviews in Toxicology. 2006;36(8):609-662.