How did all the Mercury End up in the Fish?

Fact: Mercury is highly toxic and is the only metal known to be liquid at standard pressure and temperature.

Recent articles published about whaling in both the Faroes and Japan are littered with warnings that whale meat is full of mercury, it is advised, therefore, that pregnant women and young children do not eat such meat, but what is it that is making not only whale meat but also fish meat to have such high levels of mercury in their bodies and what does it mean to you?

Mercury itself isn’t that dangerous, it is naturally found in low levels in rock, soil and water throughout the entire world. But today half of all mercury found in the atmosphere comes from burning fossil fuels like coal, oil and natural gas, with other contributions from mining, incineration of waste and various other industrial activities. This mercury pollution will either fall directly into the sea or will remain on land only to be washed into waterways, which eventually end up in the sea. In this form mercury still isn’t that dangerous because all living things can get rid of it very quickly. HOWEVER bacteria can convert mercury very quickly into a highly-toxic form called methylmercury.

The food chain then takes over here, the methylmercury is absorbed by phytoplankton which get eaten by zooplankton, these are then feasted upon by small fish and onward and upwards as the amount of toxin grows in ever larger quantities through the food chain. The largest predatory organisms in the sea like sharks, whales and swordfish, can have mercury concentrations in their muscles (the bit we humans eat) that are 10 million times higher than those of their surrounding habitat. No, that was typed correctly, 10 million times!

Above all these methylmercury fish in the food chain is the human, and accordingly nearly all the methylmercury that we accumulate over our lives come from the seafood we eat.

There is still a lot to be learnt about the effect of methylmercury on adults, it is possible that susceptibility to mercury could be genetic, or the result of diet or stress. However there is very little debate that methylmercury posses a great danger to unborn babies, infants and children. Their growing brains and nervous systems can be seriously affected by the mercury.

So what do we do to save ourselves from methylmercury? Well there are two answers; changes to the world’s energy supply and simpler consumer choices.

The US are planning to cut back on their mercury emissions which is good news and is one step towards safer fish for everyone, however in Asia about ten steps have been take backwards as 2/3 of human-generated mercury now originates from the rapidly industrializing region.

As far as consumer choice is concerned the best answer is not to avoid seafood but to avoid mercury. The FDA mercury guidelines are nothing short of confusing and many of their suggestions are… questionable but you can always try online mercury calculators from NRDC and Turtle Island Restoration Network. Or check out a graphic here which clearly illustrates the fish with the highest and lowest levels of mercury in their system and also suggested monthly servings.

It just goes to show how closely knit and linked the food we eat, the energy we use and the water all life depends on is so inextricably and undeniably linked to one another.

Mercury should be considered as one more reason why the world should shift from using fossil fuels to more renewable means of power.

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