The Making of the Eat-fish-(ad)wiser

The Eat-fish-(ad)wiser was an indirect result of my research on plastic waste in our oceans. At one point I found an article on Google describing how mercury particles in the air (mostly originating from coal fired energy plants and other industries) end up in the ocean and accumulate in algae and other micro-organisms. As plastic is a favorite habitat for such small organisms, drifting plastic waste soon is bound to become a veritable mercury mine.

This got me thinking of further links in the food chain, cause fish are known to feed on the prolific plankton tied to nicely visible plastic waste particles. Soon I found myself discovering fish species after fish species that indeed showed high mercury concentrations in various body parts.

Why not systematize the known data for the benefit of consumers, I reasoned. I ran into the American websites of the Environmental Defense Fund (, Health Alert) and the Monterey Bay Aquarium ( providing that very service. But I also discovered that a similar consumers’ guide was lacking for the European market.

So I set out collecting media articles as well as scientific and official government publications dealing with contaminants, both in wild and in farmed fish.

Two important ones were a PhD thesis on contaminants in commercial fish species by the Belgian scientist Isabelle Sioen and the WWF/North Sea Foundation consumers’ tool Viswijzer, ranking fish according to the degree of ‘sustainability’ with which they are caught and/or bred.

I drew up a list of relevant seafood species for European consumers and ranked them according to the measured concentrations I could find in the literature. As I needed to publish without too much delay, I started out confining myself to the two most thoroughly documented types of contaminant: (methylated) mercury and dioxine/PCB-like compounds.

Because consumer safety was my starting point and because so little is known about the effects of all kinds of contamination in fish, I wielded a heavy stick. Even incidental high concentrations, led to a considerably lower safety score.

The Eet-vis-wijzer (Eat-fish-(ad)wiser) therefore is certainly not a scientific publication but a journalist’s piece of work. In the near future I plan to deepen and broaden the underlying data. I need to include several other types of contaminants and make use of many more scientific data from various international sources.