Mercury

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Changed on: 08.08.2017
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Mercury is a heavy metal that is found in the environment via natural (e.g. volcanic eruptions) and industrial processes (e.g. mining, burning coal or fuel oil). Mercury also gets into the food chain and, thus, into foodstuffs through sediments in soil and water.

We differentiate between elemental (metallic) mercury (Hg0), inorganic mercury (iHg) and organic mercury compounds, such as methylmercury (MeHg).

Elemental mercury is of no significance in food. However, inorganic mercury may be found in all foodstuffs: fish and shellfish, plant-based food products and (land) animal-based food products. Inorganic mercury that gets into water is transformed into the even more toxic organic methylmercury by bacteria. It is then ingested by various water organisms, which in turn are food sources for some types of fish. Long-living predatory fish that eat other fish already contaminated with methylmercury show particularly high concentrations of methylmercury in their bodies. Thus, methylmercury is solely found in fish and other seafood (crustaceans, clams, and squid). This form of mercury is considered very dangerous in foods. As a result, mercury is a subject discussed in connection with fish consumption.

Mercury in fish

AGES topical report: Ingestion of Mercury via Food (in German)

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Mercury is a heavy metal that is found in the environment via natural (e.g. volcanic eruptions) and industrial processes (e.g. mining, burning coal or fuel oil). Mercury also gets into the food chain and, thus, into foodstuffs through sediments in soil and water.

We differentiate between elemental (metallic) mercury (Hg0), inorganic mercury (iHg) and organic mercury compounds, such as methylmercury (MeHg).

Elemental mercury is of no significance in food. However, inorganic mercury may be found in all foodstuffs: fish and shellfish, plant-based food products and (land) animal-based food products. Inorganic mercury that gets into water is transformed into the even more toxic organic methylmercury by bacteria. It is then ingested by various water organisms, which in turn are food sources for some types of fish. Long-living predatory fish that eat other fish already contaminated with methylmercury show particularly high concentrations of methylmercury in their bodies. Thus, methylmercury is solely found in fish and other seafood (crustaceans, clams, and squid). This form of mercury is considered very dangerous in foods. As a result, mercury is a subject discussed in connection with fish consumption.

Mercury in fish

AGES topical report: Ingestion of Mercury via Food (in German)

Foods

Occurance in food

Recent research findings from Austria and the EU show that terrestrial contamination of foodstuffs -- i.e. plant-based products and products from land animals -- is very low. The majority of these foods had such low mercury concentration levels that they could not even be measured.

However, the situation in fish and shellfish is very different: concentration levels could be measured in many instances. About 80 to 100 % of the mercury in fish is methylmercury -- in shellfish (prawns, clams, squid) it is 50 to 80 percent. The remaining mercury is inorganic mercury.

Food Examinations in Austria

AGES examines mercury in fish and shellfish, as well as in foods of terrestrial origin, such as corn, fruit, vegetables, dairy products, meat, baby food, and sport and other dietary supplements. The results of the tests carried out from 2007 to 2015 are summarised in the latest Topical Report: Mercury.

No measurable levels of mercury were found in over 90 % of the 3,695 terrestrial samples (plant-based products, products from land animals) carried out. Increased values were found sporadically in dietary supplements and in one cep mushroom (porcini mushroom).

A total of 1,751 specimens taken from fish and shellfish were also examined. The samples taken from freshwater fish came mainly from trout, carp, char and pikeperch from both local waters and imported products. Additionally, exotic freshwater fish, such as iridescent shark, Tilapia and popular sea fish, such as tuna, cod, herring, mackerel, sardines, anchovies, plaice, gilthead sea bream, halibut, Alaska pollock, sea bass, pollock, sprats, snappers and butterfish. An additional focus was crustaceans (prawns), water molluscs (squid, clams) and fish products (fish fingers and surimi). Moreover, individual samples were tested from over 30 other species of fish. The maximum levels permitted were exceeded in seven sea fish.

Health Effects

Health Effects

There are different forms of mercury, each having a different effect on our health. Inorganic mercury concentrates mainly in the kidneys. It can also affect the liver, nervous system, reproductive system and immune system. Methylmercury can get past the blood-brain barrier and the placenta, resulting in neurological damage. The neural system development in unborn children is easily affected by methylmercury.

Methylmercury was responsible for the mass poisoning of people in Minamata (Japan) in the 1950s, when industrial waste containing mercury was dumped in the sea. The methylmercury became concentrated in local fish and shellfish, the main food sources of the coastal population. High intake levels lead to a large number of acute poisoning cases, resulting in irreversible, neurological disorders, deaths and brain damage in newborns.

The mining of ores containing mercury was stopped in the EU from 2000 (Environmental Agency Austria, 2014). The United Nations also decided on measures to reduce worldwide mercury emissions as part of the Minamata Convention in 2013. This convention also includes a ban on activating new mercury mines and an exit plan for existing mines, among other measures (UNEP, 2013).


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