The mercury that humans are exposed to comes in a number of different forms:
1. Elemental Mercury is insoluble in water, a liquid at room temperature and poorly absorbed from the gastrointestinal tract. It vapourizes very easily and is more readily absorbable and dangerous as a vapour.
2. Inorganic Mercury Salts are also poorly absorbed.
3. Organic Mercury Compounds are converted from elemental mercury and inorganic mercury by micro-organisms and human blood enzymatic reactions and they are readily absorbed.
The symptoms of mercury toxicity depend on the type of mercury and the type of exposure (acute or chronic).
Elemental Mercury is also known as metallic mercury or quicksilver. It is readily absorbed in vapour form and accumulates in the brain, kidneys, lungs and fatty tissues causing cellular dysfunction and inflammation. It accumulates in the central nervous system and damages brain cells.
Acute Mercury Exposure can cause the following symptoms to develop within hours:
Cough; a tight feeling in the chest; chills; fever; weakness; salivation;, nausea; vomiting; diarrhoea; and a metallic taste in the mouth. Acute exposure can cause pneumonia; emphysema; the incomplete expansion or collapse of the lungs; lung damage or destruction; anaemia; damage to the cilia (the tiny, waving, and hair-like structures that move small objects through the nose, bronchi, fallopian tubes & male epididymis) and pulmonary oedema. Permanent damage to the lungs and psychological and neurological symptoms can occur.
Chronic Mercury Vapour Exposure over a period of weeks, months or years can cause the following symptoms:
Psychological and neurological symptoms including tremors and erethism (anxiety, emotional instability, irritability, depression, forgetfulness, insomnia, regressive behaviour). Problems with the mouth, teeth and gums, nausea, vomiting, diarrhoea, tunnel vision, dim or double vision, muscular weakness, anorexia, loss of sense of smell, headache, vertigo, inflammation and pain of the peripheral nerves, proteinuria, excess or lack of urine, chronic lung congestion, damage to the cilia, low grade fever and dermatitis. It can also cause chest pain, breathing difficulties, irregular heartbeat and pulse, and problems with blood pressure. Other symptoms include oedema, numbness and tingling and in some severe cases, bipolar disorder.
Inorganic Mercury Salts include mercurous chloride (also known as calomel), mercuric chloride (a corrosive poison), mercury fulminate (used in explosive detonators) and mercuric sulphide (vermilion, a high-grade paint pigment).
Acute Inorganic Mercury Salt Exposure can cause the following symptoms:
Mercuric chloride is corrosive and may produce severe nausea, vomiting, vomiting up blood, strained and painful bowel motions and urination, abdominal pain, metallic taste in mouth, bloody diarrhoea, colitis, and damage to the mucous membranes. Dehydration and cardiovascular collapse may follow. There are red blood cells, casts and protein in the urine, a decrease in or an absence of urine production and kidney failure develops.
Chronic Inorganic Mercury Salt Exposure can cause the following symptoms:
Symptoms are similar to chronic mercury vapour exposure including tremors, erethism, ataxia, slurring of speech, mouth and digestive difficulties, excessive salivation, loosening of teeth, anxiety, insomnia and mental deterioration. Intra-uterine exposure to inorganic mercury may result in tremors and involuntary movements in the infant.
Organic Mercury Compounds include methyl-mercury, ethyl-mercury including ethylmercurithiosalicylate which is also called Merthiolate or thimerosal, phenyl-mercury (merbromin which is also known as mercurochrome), and alkyl mercury halides.
Organic Mercury Compounds cause symptoms that vary with the type of compound:
Methyl mercury exposure may trigger symptoms that occur weeks to months later. The symptoms are primarily neurological. Symptoms include lack of coordination, unsteadiness, tunnel vision, blind spots in the eyes, numbness & tingling, chronic mental & physical weakness and fatigue. Other symptoms include loss of libido, death of spermatozoa, hearing loss, pain in the joints, memory loss, depression, mental deterioration, emotional instability, involuntary movements including tremors, writhing movements of the hands and arms and abnormal muscle contractions, paralysis and coma.
Intra-uterine exposure to methyl mercury has resulted in impairment of motor and mental development to various degrees, with cerebral palsy, deafness, blindness, microcephaly, fretfulness, irritability, and excessive crying described.
Ethyl mercury can produce gastrointestinal symptoms and renal damage in addition to the central nervous system symptoms of methyl mercury.
Alkyl mercury halides irritate the eyes, mucous membranes, and skin and may cause dermatitis and burns.
Phenyl mercury produces the symptoms of inorganic mercury exposure although a much smaller dose is needed because it is absorbed 4 times better via the gastrointestinal tract than inorganic salts are.