Rising Mercury Levels in Our Food Is Grave Cause For Concern


The United Nation’s Environment Programme has recently released The Global Mercury Assessment 2013, which reveals that localized gold mining operations have doubled in South America, Africa and Asia since 2005.

Mercury is often used by small-scale gold miners because the metal binds to gold, allowing it to be extracted from the surrounding minerals, after which, the mercury is burned away. This is an inexpensive method of gold extraction (mercury-free alternatives are often more costly), and it is believed this method will continue to expand during this decade, so long as the price of gold continues to rise.


Coal also contains variable concentrations of mercury, and since the Industrial Revolution there has been a steady increase of mercury emissions into the atmosphere and oceans. Today, in Southern and Eastern Asia, rapid rates of industrialization have led to these areas producing almost half of the world’s annual mercury emissions due to this region’s reliance on coal combustion for power generation and an increase in small-scale gold mining. The report also shows that the rates of mercury emissions in Latin America and Sub-Saharan Africa are also rising, although there is a reduction in North America and Europe.

In the past, pollution incidents have demonstrated the problems that arise when mercury is released into the environment. It would be wise to learn from the lessons of history and take measures to prevent mercury poisoning events from occurring again; lessons that should also be remembered when implementing climate change policies, rather than relying – predominantly – on computer models and projections.

Toxic Chemistry

Years ago, a typical school science experiment involved playing with beads of mercury – also known as quicksilver – to observe the element’s chemical properties. Today, however, even thermometers, which would have typically contained mercury, are being phased-out and usually contain alcohol or other less-hazardous substances. Liquid at room temperature, mercury is an extremely toxic heavy metal that readily evaporates. Despite this, the metal is still used in medical and electrical equipment, batteries, light bulbs and some cosmetics. When ingested or inhaled, mercury can affect the biochemistry of the neurones that comprise the central nervous system, which can lead to itching, numbness, insomnia, sight, hearing and speech impairment, a lack of co-ordination, coma and ultimately death. Inside the body, the element also seriously affects the respiratory, digestive, urinary, and immune systems, and is particularly toxic to developing embryos, especially as the element can be passed from mother to fetus. In nature, mercury can be found in a range of substances, including minerals frequently used in industrial processes, such as limestone and coal. Today, metal working, mining, cement production and the burning of coal are all responsible for the release of mercury into the atmosphere.

Chain Reactions

Another major problem with mercury is that it accumulates in the environment. Studies from the United Nations suggest that the level of mercury in the upper 100 meters of most marine systems have doubled over the last 100 years. This is because mercury is absorbed by living tissues, and thus bio-accumulates along marine food-chains, which is significant considering some 2.5 billion people – especially in Latin America, Africa, Asia and Oceania – rely on fish consumption as a main source of dietary protein. Microscopic plankton absorbs small amounts of mercury from the surrounding sea water. Such organisms at the base of the food chain are consumed by molluscs, crustaceans or small fish, allowing the mercury levels to become concentrated. These animals are further eaten by squid and larger fish, which are subsequently consumed by top predatory fish (such as sharks, mackerel, tuna, swordfish and marlin – all highly prized by humans), at which point the mercury levels have concentrated and can be dangerously high; and once ingested, around 95% of the element is absorbed by the human body. And this is not the first time that a major mercury poisoning event has entered the marine food-web and devastated coastal human communities.

Initially a producer of fertilizers during the early 20th century, the Chisso Corporation Chemical Factory, located on the shores of southwest Japan, changed its production to synthesise hydrocarbons. By the 1930s and 1940s, the factory became one of the most advanced in Japan, boosting the local economy and employing around a quarter of the population from the neighbouring town of Minamata. One of the main chemicals the factory produced was a hydrocarbon called acetaldehyde. To make this substance, mercury sulphate is used as a catalyst; this results in small quantities of organic mercury being produced as a by-product, which was discharged with the wastewater into Minamata Bay.

In April 1956, local doctors were confused by the symptoms of a five-year old girl from Minamata, who could not walk or talk properly and suffered from convulsions. Soon it was discovered that the girl’s sister and several neighbours suffered from similar symptoms and by May that year, an epidemic of an unknown disease affecting the central nervous system was reported – this was to be known as Minamata disease. As the months progressed, specialists came to observe more patients suffering from numbness, weakness and sight and speech problems; cat and fish fatalities and dead seaweed was also noted. By October 1956, 40 patients were reported with extreme symptoms of insanity and paralysis, 14 of which had died. Specialists realized that the victims were consuming fish and shellfish from the bay, and suspected heavy metal poisoning. Accordingly, the wastewater from Chisso was tested, which revealed dangerously high levels of mercury. Chisso finally closed in 1968, and today, over 2,200 victims have been officially certified as suffering from mercury poisoning, caused by consuming contaminated fish and shellfish due to the Chisso discharges and the congenital effects from poisoning; it is thought that over 1,700 individuals have died.

Regulating Harmful Emissions to Combat other Environmental Problems

We are aware that unregulated emissions of carbon dioxide, methane, and other greenhouse gases could have detrimental effects on global weather patterns and that computer projections predict large-scale climate changes. Even so, the Earth’s climate has passed through major shifts throughout geological time and carbon dioxide and methane are gaseous components of the atmosphere. The releases of heavy metals, however, such as mercury, as well as cadmium, lead, arsenic and so on, are extremely damaging to the environment and human health. Undeniably, it is important to be concerned about greenhouse gas emissions. Yet regulating the releases of heavy metals are also important, and indeed, could secondarily help control the release of greenhouse gases, such as those emitted from coal burning and industrial processes.

In Geneva this week, the United Nations aims to finalize negotiations to form an agreement to cut anthropogenic mercury emissions and reduce global mercury demands by 2015. However, because the majority of current mercury releases originate from the developing world, any proposed regulations will not only pose problems with implementing legislation, but also affect regional socio-economic growth, which often relies on burning fossil fuels and small-scale mining.

Whether there will be further disasters, such as the events that happened in Minamata, are yet to be known – but it is likely that the problems posed by rising mercury levels in the oceans and our seafood have still yet to surface.