Mercury: answering some of the current controversies about it (page 1 of 5)
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Elemental mercury
Elemental mercury (Hg) is a metallic liquid under normal conditions, and has been used in thermometers and sphygmomanometers. Ingestion of liquid elemental mercury is of low toxicity, since it is very poorly absorbed from the gastrointestinal tract. Therefore broken oral or rectal thermometers are usually of little toxicological significance, unless the patient has significantly reduced gastrointestinal transit time, or has ingested very large amounts of elemental mercury. However, if the contents are spilled onto a surface such as a carpet and the vapour is then inhaled over a period of time, systemic absorption and toxicity can occur. It is important that a vacuum cleaner is not used to clean up spilt elemental mercury, due to volatilisation of the mercury and inhalation of the vapour. Spilt elemental mercury can be cleaned up using specialised kits available from most chemists and these include instructions on its safe disposal. It is poorly absorbed following dermal contact.
Toxicity from elemental mercury occurs from volatilisation of significant quantities since it is freely absorbed through the respiratory tract epithelium. Initial symptoms include nausea, vomiting, acute breathlessness, pyrexia, headache and visual disturbances. Patients may also complain of a metallic taste and associated hypersalivation. Respiratory symptoms can progress to pulmonary oedema and respiratory failure. Patients will require good supportive care, with ventilatory support if significant respiratory symptoms occur. Blood and urinary mercury concentrations should be obtained and chelation therapy may be required, following discussion with a clinical toxicologist. Patients who develop severe respiratory symptoms and survive, may develop late sequelae, including interstitial fibrosis and residual restrictive pulmonary disease
Chronic exposure to elemental mercury can lead to non-specific symptoms, which include gastrointestinal disturbances, headache and neurological features including depression, irritability, insomnia, confusion, forgetfulness and intellectual deterioration. Chronic exposure can occur following repeated oral ingestion of low concentrations of mercury or by wrongly using a vacuum cleaner to clean up elemental mercury spillages, where the mercury continues to be vaporised each time it is used. Blood and urine mercury concentrations should be measured following discussion with a clinical toxicologist; chelation therapy may be required.
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