Is Mercury in Fish Bad for You?

From trans fats to e-numbers, there are a range of things in in food that can be harmful to us. We’re becoming increasingly aware of these damaging components, but what sometimes slip under the radar are chemicals making their way into food before production. One example is mercury, which gets into all the fish we eat. How much? How does it get there? And what risks does it pose? Keep reading to find out.

Entering the food chain

Water pollution is an easy way for pollutants to make their way into the food chain. Once it has polluted tiny organisms like algae and plankton, it can make its way into small fish that feed on them and further up the food chain. This is exactly what happens with mercury.

It is released mostly by industrial activity into rivers or seas. After being converted into methylmercury by bacteria in the water, it is absorbed by algae and subsequently eaten by the likes of shrimp and krill. These organisms are eaten by small fish, which are eventually eaten by bigger fish, which are preyed upon by even bigger fish. You get the idea.

Because of biomagnification – chemicals increasing in concentration when they are ingested by fish at each step of the food chain – larger fish tend to have more methylmercury than smaller fish. This can vary, of course, based on the location of the fish.

The effects of mercury

While mercury on its own has been linked to effects on the nervous system, it does not impact all people equally. For most people, the benefits of eating fish outweigh, and possibly counteract the mercury content. But there are some risks for foetuses when pregnant mothers eat fish.

According to the World Health Organisation, the methylmercury can have an adverse effect on the growth of a baby’s nervous system and brain. While pregnant and breast-feeding mothers should continue eating fish, they should avoid high-mercury fish like swordfish and eat no more than two portions of oily fish per week.

Testing mercury in fish

To avoid excessive consumption of mercury, we need a sound understanding of the mercury content in seafood. So far, we know that swordfish are best to avoid. But mercury levels can vary depending on different populations of fish. ‘Accurate Analysis of Low Levels of Mercury in Fish Using Vapour Generation AA’ explores how we can optimise methods of mercury detection in fish.