The ‘diabolical spiral’ of tuna: this is how you end up eating a contaminated fish

Part of the polluting components of our electronic devices end up in the meat of some fish consumed in Europe.

A tuna steak ready to be devoured.

Who does not have a mobile phone, a tablet and even an electric car? Who doesn’t complain when their electronic devices they begin to charge worse and decrease the durability of their batteries? How often do we change our electronic devices?

But who knows how and where the materials needed to make those batteries come from? Who knows what happens to the devices we throw away? The electronic devices that we all have are a complex mixture of hundreds of materials. Among which are heavy metals such as lead, mercury or cadmium.

To give you an idea, a mobile phone has between 500 and 1,000 different compounds. In addition, it must be known that obtaining these materials puts the health of the workers who extract the metals in the mines and manufacture the products at risk. And at the end of their useful life, if these materials are not treated properly, the hazardous substances they contain can pollute the environment and affect people’s health.

a vicious circle

Most of the metals needed for the production of electronic devices are mined in developing countries, such as Africa. Once obtained, they are bought by large Asian companies to produce the components of electronic devices.

Ultimately, the smartphones, tablets and electric cars produced will be sold worldwide. Although hehe majority of consumers will live in developed countries, such as those in North America and Europe.

But this is not all. When our electronic devices are already obsolete and their battery does not last long enough, the journey of heavy metals that began in the African mines ends with shipping our electronic waste back to the African continent.

Rich countries will pay poor countries to take care of their garbage, being an important part of their economy. But causing a big environmental problemsince recycling in these areas is not sufficiently developed.

The Ghana Landfill

For example, in Ghana, a West African country, there is one of the largest e-waste dumps in the world, and receives mainly European e-waste. In this landfill, technological waste accumulates to be later burned.

That waste can start to decompose, producing gases that go into the atmosphere and liquids that will soak into the ground. Its burning will also emit dangerous gases that pass into the atmosphere. Previous studies have already shown that the Ghanaian e-waste dump causes a significant soil contamination and the atmosphere by heavy metals.

However, the local populations are unaware of the environmental problems that this electronic waste produces, breathing those gases and consuming the surrounding natural resources. There is no prior health control.

Pollution returns to Europe

The return of European electronic waste to African countries closes a circle that is a clear example of current global politics: the first world extracts what it needs and returns what it no longer wants.

The enormous environmental cost of the metals needed to satisfy the growing need for electrical and electronic devices in developed countries is being paid by waste-producing and receiving countries in Africa. In the meantime, European states benefit from new gadgets and green transport carbon-free thanks to electric cars that carry African minerals in their batteries.

But perhaps that circle is not perfect and this contamination is reaching European citizens. Seafood could be a possible vector of heavy metal contamination between Africa and Europe.

Heavy metals produced in mining areas and e-waste dumps reach coastal waters through rivers and streams and accumulate in marine sediments. From there, they will enter the food chain through plankton. They will then move on to the fish that consume that plankton, eventually ending up with the big predators. The accumulation of these polluting metals will depend on the species, depending on their trophic level, their life history and their feeding habits.

Tuna with heavy metals

An example of a highly predatory fish that accumulates heavy metals is tuna. This fish is not recommended for children and pregnant women due to the high content of mercury that it can present. The presence of metals in these fish depends on the species, sex and the area in which it develops.

Fish caught in African waters enters world trade and can be sold anywhere, appearing on the European market. The sustainable fisheries partnership agreements of the European Union allow Union vessels to catch tuna as it migrates along African waters. Therefore, if African heavy metal contamination reaches tuna in the open sea through river pens and the food chain, Europe could be consuming heavy metal pollution through the ingestion of marine species caught in African waters.

What would we obtain if we analyzed tuna from different fishing areas and marketed in Spain? Would the metals extracted in African mines, present in electronic waste, be concentrated in tuna coming from African waters? The answer is yes. The results of a study we recently published show higher concentrations of all metals analyzed in tuna caught in African waters, especially mercury and lead.

Furthermore, the concentrations of metals in the tuna are related to the concentrations found in the waters where they were caught, showing that the fish are incorporating the metals present in the environment in which they live.

What can we do?

Now that we know that the ocean returns everything we send to it, and that it may be damaging our health, what can we do? Some good examples would be to study in depth how metal pollution passes from rivers and land to the sea, how these metals accumulate in the marine food chain, the risk of ingesting heavy metals through the consumption of contaminated seafood with metals from mining and electronic waste and work towards improving the treatment of electronic waste in producing and importing countries.

*This article was originally published on The Conversation.

**Alba Ardura Gutiérrez is a postdoctoral researcher in the Genetics Area of ​​the University of Oviedo.

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