Why we need action on mercury – now

The Minamata Convention entered into force in August this year and recently the parties to the Convention held their first meeting. The delegates went home with the intention to “make mercury history.”

Some of the potential history makers are from the 70 or so states where the use of mercury in artisanal and small scale gold mining has been steadily increasing. They face a big challenge to eliminate mercury from a largely unregulated activity where it is valued for its low cost and simple use in the extraction of gold. But replacing mercury with one of the available safe options is a matter of life and death for many miners and their families. It also has major implications for aquatic ecosystems and health of people living in the north.

The mercury released from gold mining activities in South East Asia is recognised as the major source of mercury to the Arctic and sub-Arctic regions. It contributes to increasing levels of mercury in fish, marine mammals and people in these areas. One of the main consequences is that an estimated 60 thousand children are born each year in Nordic countries with mercury levels that can cause developmental damage.

Everyone around the globe wants the best possible future for children. The elimination of mercury emissions from gold mining – one of the primary goals of the Minamata Convention – will reduce the exposure of every child to toxic mercury, no matter where they live.

Health and cost implications for northern peoples

Scientific studies suggest that a large proportion of the mercury emitted to the atmosphere from artisanal and small scale gold mining comes to rest in the Arctic and Sub-Arctic regions. It makes its way into rivers, lakes and the ocean and mercury levels in fish, shellfish and marine mammals are continually increasing. Nowadays people consuming diets high in seafood can potentially ingest damaging amounts of mercury. A powerful neurotoxin, mercury readily passes through the protective blood-brain barrier, damaging the central nervous system. Unborn children and babies are especially at risk because mercury can cross the placenta into the foetus where it accumulates in the brain and other tissues. It can also be passed to babies through breast milk.

Everyone has some mercury in their body but the World Health Organisation recognises that even small amounts can cause serious health problems. Consequently, they have set a safe limit of 0.58 µg/g* – below which, for example, current evidence suggests there is no substantial risk of developmental neurotoxicity (e.g. deficits in fine motor skills, language and memory). However, many children around the world are exposed in utero to unsafe levels of mercury. This is the case in Norway, Sweden, Denmark and Finland, where each year nearly 60,000 children are born who have been exposed to mercury levels that can result in long-term intelligence quotient (IQ) deficits. Minor IQ losses may go unnoticed in an individual, but on a large scale they can cause an important shift in the intellectual capacity of a community or population. IQ loss is not the only documented effect of neonatal mercury exposure – there are many other health impacts such as cardiovascular disease.

The economic costs of projected wage losses and medical expenses related to prenatal mercury exposure have been calculated. For example, across Norway, Sweden, Denmark and Finland these costs are estimated at 180 million euros annually. So, in addition to the health improvements that will stem from reducing global mercury emissions, the need for action is highlighted by the potential widespread economic benefits from the Minamata Convention. This action is especially critical in supporting the many developing states that signed on to the Convention and committed to drastically decreasing mercury emissions.

How does mercury get from tropical gold mines into Arctic fish?

Artisanal and small-scale gold mining is confined to places where people mostly use simple tools to separate small amounts of gold from sediments and rock. Many of these miners mix mercury with the crushed gold ore to form an amalgam. This amalgam is heated to drive off the mercury, leaving behind the gold. The mercury forms a toxic plume that remains in the atmosphere, carried by the wind for up to two years. In this way mercury vapour can be transported long distances.

At the beginning of every Arctic spring something happens that causes the mercury that has been circulating in the atmosphere to rain out of the sky. The mechanism by which this occurs is similar to the one responsible for producing the hole in the ozone layer – with the help of sunlight, the mercury in the atmosphere is oxidized. This oxidised mercury is quickly deposited on ice, soil and water surfaces. But this process occurs mostly around the coast and does not account for the very high concentrations of mercury found in river systems in the Arctic.

A recent study has suggested that a large part of the mercury entering the Arctic Ocean could involve tundra vegetation. Monitoring in the Arctic has revealed that during the summer there is an increase in the uptake of atmospheric mercury by vegetation, with much of this mercury eventually ending up in the tundra soil. The contaminated soil washes into the river systems which transport the mercury to the ocean. This movement of mercury could be the most important pathway for mercury entering the aquatic ecosystems in the Arctic. These are complex processes we are just beginning to understand.

Turning it toxic

After its long journey in the atmosphere, mercury can undergo a transformation that makes it extremely toxic to people and other living organisms. Bacteria in soil and water convert the inorganic mercury to methylmercury, the form in which it most easily makes its way into the food chain.

Mercury contaminated seafood

The majority of human exposure to mercury comes from the consumption of seafood. Fish eat contaminated algae and other vegetation that convert mercury into its most toxic form – methylmercury. Once ingested, fish protein retains more than 90% of the methylmercury. These fish are in turn eaten by other fish and so the mercury content progressively increases as you move up the food chain – a process known as biomagnification.

Eating fish provides many recognised health benefits and consumption is encouraged as part of a balanced diet. Many fish species in the Arctic and sub-Arctic contain mercury levels well below toxic levels. However, most health authorities advise that pregnant women and small children should avoid or limit eating long-lived and predatory fish and marine mammal species such as beluga, seal, canned albacore tuna, shark, king mackerel and swordfish, as these can contain high concentrations of mercury. Species like salmon, cod and Arctic char, generally have low levels of mercury. It is thought that mercury concentrations in fish and seafood respond proportionally to changes in atmospheric inputs, so reducing the amount of atmospheric mercury reaching the Arctic and sub-Arctic will reduce mercury concentrations in all fish.