Mercury, the only liquid metal at room temperature, has long been known for its dual nature. While elemental mercury found use in medical therapy, mercury toxicity has also been appreciated from the Middle-Ages. Mercury toxicity results when this heavy metal interferes with critical cellular enzymes and functional proteins. All three forms of mercury, elemental, inorganic and organic, have unique patterns of toxicity.

Elemental mercury, used in traditional remedies, dental amalgam, barometers, thermometers and photography, can cause toxicity when absorbed as vapors through the lung. Even a small accidental spill of elemental mercury can result in acute toxicity. Effects of elemental mercury toxicity are mainly seen in the lung and the brain. The airways and alveoli of the lung become irritated, leading to bronchitis and pneumonia. In severe cases respiratory failure presents with cough, breathlessness and low oxygen levels in blood. Involvement of the central nervous system in mercury toxicity causes convulsions and headache. Ingestion of elemental mercury does not cause mercury toxicity as long as the intestinal mucosa is normal. However, people with gut problems like gastrointestinal disorders like diverticulosis and fistula may be at risk of mercury toxicity after ingestion.

Besides the tremors, irritation of the oral cavity, excessive salivation and sweating, chronic elemental mercury toxicity causes some unique symptoms labeled as erethism. It includes extreme shyness, emotional instability, nervousness, insomnia, memory problems, and an inability to concentrate. Signs of chronic toxicity may even mimic Parkinson