Mercury and health

Mercury is considered by WHO (The World Health Organisation) as one of the top ten chemicals or groups of chemicals of major public health concern.

Key facts

  • "Mercury is a naturally occurring element that is found in air, water and soil.
  • Exposure to mercury – even small amounts – may cause serious health problems, and is a threat to the development of the child in utero and early in life.
  • Mercury may have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.
  • People are mainly exposed to methylmercury, an organic compound, when they eat fish and shellfish that contain the compound." (1)   

What is mercury?

Mercury is a natural element found in the earth's crust and exists in various forms:

  • elemental (or metallic) and inorganic (to which people may be exposed through their occupation)
  • organic (e.g., methylmercury, to which people may be exposed through their diet)

Mercury can be released into the environment from a range of natural (volcanic activity and weathering of rocks) and human activities such as mining, coal-fired power stations, waste incinerators, home heating and cooking with coal based products and various industrial processes. 

Bacteria in the environment can transform mercury into organic methylmercury which can then accumulate in the food chain as plankton or shellfish are eaten by fish, which are eaten by larger fish and then by humans.

Mercury is not affected by heat so cooking doesn't protect us from mercury in our foods.

What effects does mercury have on health?

Mercury in all its forms is toxic to humans and animals resulting in damage to our nervous, digestive and immune systems, lungs, kidneys, skin and eyes. The severity can be mild through to fatal.  

Symptoms and signs of mercury toxicity

Symptoms of mercury exposure or toxicity can include:

  • tremors
  • insomnia
  • memory loss
  • skin and eye burns from direct contact to corrosive inorganic salts of mercury
  • gastrointestinal damage from ingestion
  • neuromuscular effects
  • headaches
  • cognition and thinking difficulties
  • behavioural disorders
  • motor dysfunction
  • proteinuria through to kidney failure
  • and more.

Who is most at risk?

Anyone can be exposed to mercury poisoning, but three groups are at higher risk:

  1. Pregnant women and their unborn babies as mercury is toxic to their developing brains (results in learning difficulties, poor coordination, attention, vision and cognition problems)
  2. Workers in industrial activities where mercury can be released into the environment or the vapour inhaled
  3. Low-income populations where fish and shellfish are a stable food. 

Sadly there are many examples of fishing communities in countries such as Brazil, China, Canada, Columbia and Greenland where children show signs of mental retardation due to mercury exposure from eating fish. Other well known mercury poisonings include Minamata, Japan, where a factory discharged waste liquid into Minamata Bay containing high levels of methylmercury from acetic acid production between 1932 to 1968. It took many years to realise the strange disease (later known as Minamata disease) so many locals were getting was due to mercury in the bay's fish and shellfish.

Prevention – how to reduce human exposure to mercury

The World Health Organisation and other large groups have identified key changes to reduce and prevent mercury exposure. These include:

  • promoting the use of clean energy sources that do not burn coal 
  • stopping the use of mercury in gold mining
  • eliminating the mining of mercury
  • phasing out non-essential mercury-containing products such as batteries, thermometers, dental fillings, lamps, skin lighting products
  • careful recycling of mercury 
  • safer work practices where mercury is used.

Read more about global measures to reduce mercury exposure. World Health Organisation.

Cleaning up mercury spills in your house

If a mercury thermometer breaks (or other items containing around ¼ teaspoon or less of mercury), you may be able to clean it up yourself by following the Ministry of Health information sheet.

If you spill more than this amount, you should follow this advice and seek help from professional hazardous waste disposal companies to clean up the spill. Contractors can be contacted through the Yellow Pages under “Waste Disposal”.

View the Ministry of Health advice about mercury spills. 


  1. Mercury and food fact sheet World Health Organisation, July 2013
  2. Public health round up  Bulletin of the World Health Organisation Vol 91 (3) March 2013
Credits: Health Navigator team.