Guidance

Mercury: general information

Updated 8 June 2022

Overview

Mercury occurs widely in the environment, owing to natural and human processes. It is present in 3 forms, namely elemental (metallic) mercury, inorganic and organic mercury. This general information section will focus on elemental and inorganic mercury only.

Elemental mercury is a shiny, silver-white liquid metal at room temperature and may also be referred to as quick silver. It evaporates to form mercury vapour, which is the predominant form of mercury in the atmosphere.

Inorganic mercury compounds contain mercury combined with other elements: mercuric sulphide contains sulphur; mercuric oxide contains oxygen; and mercuric chloride contains chlorine. These compounds are mostly white powders or crystals.

Uses of mercury

Elemental mercury is used in the electrolysis of sodium chloride, to make caustic soda and chlorine and in extracting gold from ores. It is used to make lamps, electrical switches, thermometers and barometers.

Some types of dental amalgam (used in dental fillings) also contain elemental mercury. Inorganic mercury compounds have been used in pharmaceuticals, preservatives, fungicides and antiseptics although their use in these areas has been largely discontinued over the last few decades. Inorganic mercury may also be found in illegal skin-lighteners and traditional medicines.

How mercury gets into the environment

Small amounts of mercury exist in the environment in soil, water and air owing to natural and human (anthropogenic) processes.

The major natural sources of mercury in the environment are degassing from the earth’s crust, emissions from volcanoes and evaporation from water bodies.

Most of the mercury released from man-made activities is elemental mercury released into the air due to mining, burning fossil fuels and incinerating waste. Mercury also enters the soil from fertilizers, fungicides and from solid waste such as thermometers, light bulbs or electrical switches.

Exposure to mercury

Exposure to mercury may occur from breathing contaminated air, eating contaminated food or water, or by skin contact. Everyone is exposed to mercury to a small extent from air, water and food. People may be exposed to mercury from dental amalgam used in dental fillings.

The EU Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) considered the safety of dental amalgam and concluded that dental amalgam already in place is not considered a health risk for the general population.

Spillages of elemental mercury from broken thermometers, barometers or compact fluorescent light bulbs may result in exposure to mercury vapour. Some traditional medicinal products and illegal skin lightening creams may contain mercury and their use can lead to exposure.

Occupational exposure to mercury can occur in a number of workplaces that use mercury, such as in factories making electrical equipment or thermometers, chemical processing plants and dental practices. Safe levels are enforced to protect employees who may be exposed to mercury at work. Such levels are below those that are thought to cause harmful effects.

How exposure to mercury can affect your health

The presence of mercury in the environment does not always lead to exposure. In order for it to cause any adverse health effects, you must come into contact with it. You may be exposed to mercury by breathing or ingesting it, or by skin contact with it.

Following exposure to any chemical, the adverse health impacts you may encounter depend on several factors, including the amount to which you are exposed (dose), the way you are exposed, the duration of exposure, the form of the chemical and if you were exposed to any other chemicals.

Swallowing small amounts of elemental mercury is unlikely to cause adverse health effects. If large amounts are swallowed, nausea, vomiting and stomach pain can occur.

Breathing elemental mercury fumes can cause nausea, vomiting and flu-like symptoms such as fever and muscle aches and pains. Cough, breathlessness and chest pain can also occur a few hours after exposure. Breathing in larger amounts of mercury 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.

Eye exposure to elemental mercury fumes may cause eye irritation, conjunctivitis, blurred vision and sensitivity to light. Skin itching and redness can occur following skin contact with elemental mercury.

Inorganic mercury compounds do not vaporise, hence are not generally breathed in and only small amounts may pass through the skin.

Swallowing inorganic mercury can cause stomach irritation, leading to nausea, vomiting and diarrhoea. Ingesting large amounts of inorganic mercury can cause stomach ulcers and can damage the kidneys, intestines and nervous system.

Mercury and cancer

The International Agency for Research on Cancer (IARC) found that there was not enough evidence to determine whether mercury could cause cancer in humans.

Pregnancy and the unborn child

There is little evidence on the effects of exposure to inorganic or elemental mercury during pregnancy. Therefore, is not possible to draw any definitive conclusions. Effects on the unborn child are more likely to occur at levels that harm the mother.

Children

Children may be more susceptible to the neurotoxic effects of mercury as 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. The symptoms and features of this are muscle cramps, irritability, skin redness and swelling, peeling of skin, itching, fever and sweating.

What to do if you are exposed to mercury

You should remove yourself from the source of exposure.

If you have got mercury on your skin, remove soiled clothing, wash the affected area with lukewarm water and soap for at least 10 to 15 minutes and seek medical advice.

If you have got mercury in your eyes, remove contact lenses, irrigate the affected eye with lukewarm water for at least 10 to 15 minutes and seek medical advice.

If you have inhaled or ingested mercury seek medical advice.

If you spill mercury or break a mercury-containing device

Small mercury spills (such as broken thermometer or compact fluorescent light bulb) in the home can be cleaned up as follows:

• put disposable gloves on before cleaning up the spill
• any broken glass should be carefully picked up and placed in a double-bag
• mercury droplets should be collected with sticky tape or pieces of paper and placed in a double-bag
• if the spill has occurred on bed sheets or clothing, they should be double bagged and discarded; they should not to be washed and reused
• a torch can be used to check all mercury droplets have been collected
• the room should be ventilated (as mercury can volatilise and be breathed in) for at least 24 hours
• the mercury should not, under any circumstances, be vacuumed as this can increase exposure via inhalation – if a vacuum has been used to clean up a small amount of mercury, the current advice is to ventilate the room and to double bag and dispose of the vacuum cleaner
• the disposal of the collected mercury may differ between local authorities; therefore, you should contact their local environmental health department to query appropriate disposal – find your local authority website

For spills involving barometers and other larger devices, where they may be a larger amount of mercury, you should contact your local authority environmental health department for further advice.

Additional sources of information

NHS.UK provides information on:

• skin lightening
• poisoning

The information contained in this document from the UK Health Security Agency (UKHSA) Radiation, Chemicals and Environment Directorate is correct at the time of its publication. Email chemcompendium@phe.gov.uk if you have any questions about this guidance or for other questions email phe.enquiries@phe.gov.uk