Mercury poisoning: sources, symptoms and what to do after exposure

Mercury is a naturally occurring element that is widely distributed in the environment. UKHSA describes elemental mercury as a shiny, silver-white liquid metal at room temperature that evaporates to form mercury vapour. Inorganic mercury compounds, which combine mercury with other elements, are mostly white powders or crystals. Organic mercury, a third form, is outside the scope of the UKHSA pages used here.

Everyone is exposed to mercury to a small extent through air, water and food. Poisoning describes harmful exposure, and what happens depends on the dose, how you were exposed, for how long, the form of mercury and whether other chemicals were involved. A single tiny spill and a long period working in a poorly ventilated space are very different situations.

UKHSA lists uses of elemental mercury in the electrolysis of sodium chloride to make caustic soda and chlorine, in extracting gold from ores, and in lamps, electrical switches, thermometers and barometers. Some types of dental amalgam contain elemental mercury; UKHSA reports that the European scientific committee which looked at this concluded that dental amalgam already in place is not considered a health risk for the general population.

Spillages from broken thermometers, barometers or compact fluorescent light bulbs may result in exposure to mercury vapour. UKHSA also notes that some traditional medicinal products and illegal skin-lightening creams may contain mercury and that their use can lead to exposure.

• Spills from broken mercury thermometers, barometers or low-energy bulbs.

• Factories making electrical equipment or thermometers and chemical processing plants.

• Dental practices where amalgam is handled.

• Illegal skin-lightening creams and some traditional medicines.

UKHSA says breathing elemental mercury fumes can cause nausea, vomiting and flu-like symptoms such as fever and muscle aches and pains, with cough, breathlessness and chest pain a few hours later. Larger amounts of fumes may cause lung damage and can affect the kidneys, liver and muscles. Elemental mercury can also affect the central nervous system, causing tiredness, nervousness, tremor, headaches, personality changes, memory loss and hallucinations.

With longer-term exposure by inhalation, UKHSA's toxicological overview describes neurotoxicity, with decreased psychomotor skills and symptoms including fatigue, tremor, headaches, depression, irritability and hallucinations, as well as kidney effects such as protein in the urine and mouth effects such as sore gums and ulceration of the lining of the mouth.

Swallowing inorganic mercury compounds can cause stomach irritation, nausea, vomiting and diarrhoea, and large amounts can cause stomach ulcers and damage the kidneys, intestines and nervous system. UKHSA notes that if people survive damage to the gut, acute kidney failure may occur within 24 hours of ingestion.

UKHSA says children may be more susceptible to the neurotoxic effects of mercury because their central nervous system is still developing. Rarely, some children exposed to high levels of metallic or inorganic mercury have developed a condition called acrodynia, with muscle cramps, irritability, skin redness and swelling, peeling skin, itching, fever and sweating.

There is little evidence on exposure during pregnancy, so no definitive conclusions can be drawn. UKHSA says effects on the unborn child are more likely to occur at levels that harm the mother.

UKHSA advises removing yourself from the source of exposure. If mercury is on the skin, remove soiled clothing, wash the area with lukewarm water and soap for at least 10 to 15 minutes and seek medical advice. If it is in the eyes, remove contact lenses, irrigate with lukewarm water for at least 10 to 15 minutes and seek medical advice. If you have inhaled or swallowed mercury, seek medical advice, for example by calling NHS 111, a poison information service or, if someone is very unwell, 999.

For a small spill such as a broken thermometer or bulb, UKHSA lists these steps: put on disposable gloves, pick up broken glass carefully into a double bag, collect droplets with sticky tape or pieces of paper into the double bag, double bag and discard affected bedding or clothing rather than washing it, use a torch to check for droplets, ventilate the room for at least 24 hours, never vacuum, and contact the local authority environmental health department about disposal. For larger spills, such as from barometers, contact the local authority environmental health department for advice.

Doctors consider the history of exposure, the symptoms and the examination. The sources used here do not describe testing in detail. UKHSA does note that the kidneys are a main target organ, with protein, blood or reduced volume in the urine reported after exposure, so kidney effects are an obvious thing for clinicians to look for.

UKHSA notes that elimination is mainly through urine and faeces, with a half-life of approximately 1 to 2 months, which is why exposure that has stopped may still show up in tests for some time.

The first and most important step, as UKHSA advises, is to remove yourself from the source of exposure and seek medical advice after any inhalation, ingestion or contact with eyes or skin. Further treatment is guided by a clinician or poison information service and depends on the form, amount and route of exposure.

UKHSA notes that safe workplace levels are set below those thought to cause harmful effects, which is the main protection for people who work with mercury.

On the NHS, concerns about exposure are assessed by a GP, NHS 111 or emergency department, who can seek advice from national poisons services. Workplace exposure is also a matter for employers and occupational health services, who must keep exposure below safe levels, and the Health and Safety Executive is the regulator.

Private occupational health or toxicology consultations are sometimes used for second opinions on long-term exposure. Anyone with symptoms after a significant exposure should not wait for a private appointment.